Patent Publication Number: US-2020299351-A1

Title: Antigen-Presenting Synthetic Surfaces, Covalently Functionalized Surfaces, Activated T Cells, and Uses Thereof

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Patent Application No. PCT/US2018/043146, filed Jul. 20, 2018, which claims priority from U.S. Provisional Application No. 62/664,279, filed Apr. 30, 2018; U.S. Provisional Application No. 62/660,779, filed Apr. 20, 2018; and U.S. Provisional Application No. 62/535,742, filed Jul. 21, 2017, the contents of each of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Immunotherapy offers a potentially powerful approach to treating cancers successfully. T lymphocyte activation by antigen presenting dendritic cells is one aspect of preparing tumor-targeting cytotoxic T lymphocytes for use in immunotherapy. Activation by dendritic cells may be improved by using more reproducible and better characterizable technologies. Some embodiments of the present invention include modified surfaces configured to activate T lymphocytes, related methods of using such modified surfaces to activate T lymphocytes, and compositions containing such activated T lymphocytes. 
     SUMMARY OF THE INVENTION 
     In a first aspect, an antigen-presenting surface for activating a T lymphocyte (T cell) is provided, comprising: a plurality of primary activating molecular ligands, wherein each primary activating molecular ligand comprises a major histocompatibility complex (MHC) Class I molecule configured to bind to a T cell receptor (TCR) of the T cell; and, a plurality of co-activating molecular ligands each comprising a TCR co-activating molecule or an adjunct TCR activating molecule, wherein each of the plurality of primary activating molecular ligands and the plurality of co-activating molecular ligands is specifically bound to the antigen presenting surface. In some embodiments, the plurality of co-activating molecular ligands comprise TCR co-activating molecules and an adjunct TCR activating molecules. In some embodiments, the ratio of the TCR co-activating molecules to the adjunct TCR activating molecule may be about 10:1 to about 1:20. In some embodiments, the plurality of primary activating molecular ligands may be disposed upon at least a portion of the antigen-presenting surface at a density from about 4×10 2  to about 3×10 4  molecules per square micron. In other embodiments, the plurality of primary activating molecular ligands is disposed upon at least a portion of a surface of the antigen-presenting surface at a density from about 5×10 3  to about 3×10 4  molecules per square micron. In any of these embodiments, the antigen-presenting surface can be the surface of a bead. In any of these embodiments, the antigen-presenting surface can be the surface of a wafer. In any of these embodiments, the antigen-presenting surface can be at least one inner surface of a microfluidic device. In any of these embodiments, the antigen-presenting surface can be an inner surface of a tube. 
     In another aspect, a method of preparing an antigen-presenting surface for activating a T lymphocyte (T cell) is provided, comprising: reacting a plurality of primary activating molecules, each comprising a major histocompatibility complex (MHC) Class I molecule configured to bind to a T cell receptor of the T cell, with a first plurality of binding moieties of a covalently functionalized surface, wherein each of the first plurality of binding moieties is configured for binding the primary activating molecule; and reacting a plurality of co-activating molecules, each comprising: a T cell receptor (TCR) co-activating molecule; or an adjunct TCR activating molecule, with a second plurality of binding moieties of the covalently functionalized surface configured for binding the co-activating molecule, thereby providing a plurality of specifically bound primary activating molecular ligands and a plurality of specifically bound co-activating molecular ligands on the antigen-presenting surface. In any of these embodiments, the antigen-presenting surface can be the surface of a bead. In any of these embodiments, the antigen-presenting surface can be the surface of a wafer. In any of these embodiments, the antigen-presenting surface can be at least one inner surface of a microfluidic device. In any of these embodiments, the antigen-presenting surface can be an inner surface of a tube. 
     In another aspect, a kit is provided for preparing an antigen-presenting synthetic surface for activating a T lymphocyte (T cell), including: a. any covalently functionalized synthetic surface as described herein, which includes a plurality of noncovalently or covalently associated first coupling agents; and a first modification reagent including a plurality of major histocompatibility complex (MHC) I molecules configured to bind with a T cell receptor of the T cell, and further wherein the MHC molecules are configured to bind to one of a first subset of the plurality of noncovalently or covalently associated first coupling agents of the covalently functionalized synthetic surface. In some embodiments, the first coupling agents may be a biotin-binding agent. The biotin-binding agent may be streptavidin. In some embodiments, each of the plurality of MHC molecules may further include at least one biotin functionality. In some embodiments, the kit further includes a reagent comprising a plurality of co-activating molecules, each configured to bind one of a second subset of the noncovalently or covalently associated first coupling agents of the covalently functionalized synthetic surface. In some embodiments, the co-activating molecules may be T cell receptor (TCR) co-activating molecules, adjunct TCR activating molecules, or any combination thereof. The co-activating molecules may further include at least one biotin functionality. 
     In yet another aspect, a method of preparing a covalently functionalized surface comprising a plurality of streptavidin or biotin functionalities and at least a first plurality of surface-blocking molecular ligands, wherein the method comprises: reacting at least a first subset of reactive moieties of an intermediate reactive synthetic surface with a plurality of linking reagents, each linking reagent of the plurality comprising streptavidin or biotin; and reacting at least a second subset of reactive moieties of the intermediate reactive synthetic surface with a plurality of surface-blocking molecules, thereby providing the covalently functionalized synthetic surface comprising at the least one plurality of streptavidin or biotin functionalities and at the least first plurality of surface-blocking molecular ligands. In some embodiments, if the linking reagents comprise biotin, the method optionally further comprises noncovalently associating streptavidin with the biotin functionalities. 
     In another aspect, a method of activating T lymphocytes (T cells) is provided, comprising: contacting a plurality of T cells with an antigen-presenting synthetic surface comprising: a plurality of primary activating molecular ligands, each comprising a major histocompatibility (MHC) Class I molecule configured to bind to a T cell receptor of the T cell; and a plurality of co-activating molecular ligands each comprising a T cell receptor (TCR) co-activating molecule or an adjunct TCR activating molecule; and culturing the plurality of T cells in contact with the antigen-presenting synthetic surface, thereby converting at least a portion of the plurality of T cells to activated T cells. The antigen-presenting synthetic surface may be any antigen-presenting synthetic surface described herein, e.g., an antigen-presenting bead, antigen-presenting wafer, antigen-presenting tube, or antigen-presenting microfluidic device described herein or a product of any one of the methods described herein. In some embodiments, the T cells comprise CD8+ T cells. In some embodiments, the method further comprises contacting the plurality of T cells with a plurality of growth stimulatory molecular ligands. In some embodiments, each of the growth stimulatory molecular ligands comprises a growth factor receptor ligand. In some embodiments, the growth factor receptor ligand comprises IL-21 or a fragment thereof. 
     In another aspect, a method of performing an antigen-specific cytotoxicity assay is provided, comprising: loading one or more target cells in a sequestration pen of a microfluidic device; loading one or more T cells in the sequestration pen, such that the one or more T cells can contact the one or more target cells; contacting the target cells with a detectable marker that labels apoptotic cells; and detecting whether the target cells become apoptotic. In certain embodiments, the microfluidic device further comprises a microfluidic channel, and the sequestration pen comprises an opening which opens to the microfluidic channel such that the sequestration pen is fluidically connected to the microfluidic channel. In certain embodiments, a plurality of target cells are loaded into the sequestration pen. In other embodiments, a single target cell is loaded into the sequestration pen. In certain embodiments, a single T cell is loaded into the sequestration pen. In other embodiments, a plurality of T cells are loaded into the sequestration pen. In certain embodiments, the target cell(s) and/or T cell(s) are loaded into the sequestration pen by flowing them into the microfluidic channel, then tilting the microfluidic chip and allowing gravity to pull the target cell(s) and/or T cell(s) into the sequestration pen. In certain embodiments, the microfluidic device comprises a DEP configuration and DEP force is used to load the target cell(s) and/or T cell(s) into the sequestration pen. In certain embodiments, the DEP force is activated by structured light. In certain embodiments, the detectable marker is provided in a solution that is flowed through the microfluidic channel, whereupon the detectable marker can diffuse from the microfluidic channel into the sequestration pen and contact the target cells. In certain embodiments, the detectable marker is a enzymatic substrate, such as a Caspase 3 substrate. In other embodiments, the detectable marker is a labeled antibody that specifically binds to apoptotic cells and/or apoptotic bodies. In certain embodiments, detecting whether the target cells become apoptotic is determined 2 or more hours (e.g., 3, 4, 5, 6, 7, or more hours) after contacting the target cell(s) with the detectable marker. In certain embodiments, the target cell(s) are cancer cells, such as cells from a cancer cell line. In certain embodiments, the target cell(s) are cells from a cell line that express a cancer-associated or cancer-specific antigen. In certain embodiments, the target cell(s) express an antigen associated with melanoma, breast cancer, or lung cancer. In certain embodiments, the T cells express a chimeric antigen receptor (CAR). For example, the T cells can be CAR T cells. In other embodiments, the T cells do not express a chimeric antigen receptor. For example, the T cells can be therapeutic endogenous T cells (ETCs). 
     In another aspect, a method of treating a subject in need of treating a cancer is provided; comprising: obtaining a plurality of T lymphocytes (T cells) from the subject; contacting the plurality of T cells with an antigen-presenting synthetic surface comprising a plurality of major histocompatibility complex (MHC) I molecules configured to bind to a T cell receptor of each of the plurality of T cells, wherein the MHC molecules comprise an antigen specific for the cancer of the subject and wherein the antigen-presenting synthetic surface is an antigen-presenting surface described herein or is produced according to a method as described herein; producing a plurality of activated T cells, wherein the activation is configured to be specific against the cancer of the subject; separating the plurality of specific activated T cells from unactivated cells; and, introducing the plurality of antigen-specific activated T cells into the subject. In some embodiments, the antigen-presenting surface is an antigen-presenting bead, an antigen-presenting wafer, an antigen-presenting tube, or an antigen-presenting microfluidic device as described herein. 
     In another aspect, a kit for activating T lymphocytes (T cells) is provided, comprising: an antigen-presenting surface described herein. In some embodiments, the antigen-presenting surface is an antigen-presenting bead, an antigen-presenting wafer, an antigen-presenting tube, or an antigen-presenting microfluidic device as described herein. 
     In another aspect, a kit for performing an antigen-specific cytotoxicity assay is provided, comprising: a microfluidic device (e.g., a microfluidic device having a microfluidic channel and a sequestration pen); and a reagent for detecting apoptosis. In certain embodiments, the microfluidic device is an antigen-presenting microfluidic device. The microfluidic device or antigen-presenting microfluidic device can be any microfluidic device or antigen-presenting microfluidic device described herein. In certain embodiments, the reagent for detecting apoptosis is a substrate for a caspase enzyme, such as Caspase 3. In certain embodiments, the reagent for detecting apoptosis specifically binds to apoptotic cells, such as an apoptosis-specific antibody. 
     In a further aspect, a covalently functionalized synthetic surface is provided, comprising at least one plurality of streptavidin functionalities and at least one plurality of surface-blocking molecular ligands, wherein the plurality of surface-blocking molecular ligands are covalently attached to the covalently functionalized synthetic surface, and the streptavidin functionalities are (i) covalently attached to the covalently functionalized synthetic surface or (ii) noncovalently attached to the covalently functionalized synthetic surface through a biotin moiety covalently attached to the covalently functionalized synthetic surface. In some embodiments, the covalently functionalized synthetic surface may be a covalently functionalized bead, a covalently functionalized wafer, or a covalently functionalized microfluidic device, as described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates an example of a system for use with a microfluidic device and associated control equipment according to some embodiments of the disclosure. 
         FIGS. 1B and 1C  illustrate a microfluidic device according to some embodiments of the disclosure. 
         FIGS. 2A and 2B  illustrate sequestration pens according to some embodiments of the disclosure. 
         FIG. 2C  illustrates a detailed sequestration pen according to some embodiments of the disclosure. 
         FIGS. 2D-F  illustrate sequestration pens according to some other embodiments of the disclosure. 
         FIG. 2G  illustrates a microfluidic device according to an embodiment of the disclosure. 
         FIG. 2H  illustrates a coated surface of the microfluidic device according to an embodiment of the disclosure. 
         FIG. 3A  illustrates a specific example of a system for use with a microfluidic device and associated control equipment according to some embodiments of the disclosure. 
         FIG. 3B  illustrates an imaging device according to some embodiments of the disclosure. 
         FIG. 4  is a graphical representation of T cell activation pathways according to an embodiment of the disclosure. 
         FIGS. 5A and 5B  are schematic representations of preparation of antigen-presenting surfaces according to various embodiments of the disclosure. 
         FIG. 6  is a schematic representation of the process of preparing an antigen presenting surface according to an embodiment of the disclosure 
         FIGS. 7A and 7B  are scanning electron micrograph representations of patterned antigen presenting surfaces according to some embodiments of the disclosure. 
         FIGS. 8A-8D  are graphical representations of various characterization parameters for activation of T lymphocytes at 7 days of culturing, according to some embodiments of the disclosure. 
         FIG. 9  is a graphical representation of the distribution of characteristics for activated T lymphocytes according to some embodiments of the disclosure. 
         FIG. 10  is a graphical representation of the distribution of activated T lymphocytes after a first period of stimulation and culturing, comparing the use of antigen-presenting bead activation to dendritic cell activation, according to one embodiment of the disclosure. 
         FIG. 11  is a graphical representation of the distribution of activated T lymphocytes after a second period of stimulation and culturing, comparing the use of antigen-presenting bead activation to dendritic cell activation, according to one embodiment of the disclosure. 
         FIG. 12  is a graphical representation of various characterization parameters for activation of T lymphocytes at 7 and 14 days, compared to dendritic cell activation. 
         FIG. 13  is a graphical representation of Fourier Transform Infrared spectra of a covalently functionalized polystyrene bead at selected steps of the functionalization. 
         FIGS. 14A-14D  are graphical representations of various characterization parameters for activation of T cells, according to an embodiment of the disclosure. 
         FIGS. 15A-15E  are graphical representations of cell product characterization according to an embodiment of the disclosure. 
         FIG. 16  is a graphical representation of cell product characterization according to an embodiment of the disclosure. 
         FIG. 17  is a graphical representation of cytotoxicity experiments according to one embodiment of the disclosure. 
         FIGS. 18A-180  are graphical representations of cell product characterization according to an embodiment of the disclosure. 
         FIGS. 19A-19F  are graphical representations of the characterization of activation using an antigen-presenting surface according to some embodiments of the disclosure. 
         FIGS. 20A-20I  are graphical representations of the characterization of activation using an antigen-presenting surface according to some embodiments of the disclosure. 
         FIGS. 21A-21F  are graphical representations of characterization of activation using antigen-presenting surfaces according to some embodiments of the disclosure. 
         FIGS. 22A-22B  are images of target cells taken at selected time points after being contacted with T lymphocytes and a Caspase 3 substrate in an antigen specific cytotoxicity assay according to some embodiments of the disclosure. 
         FIG. 22C  is a graphical representation of the course of an antigen specific cytotoxicity assay according to some embodiments of the disclosure. 
         FIGS. 23A-23E  are graphical representations of the characterization of the cellular product obtained using an antigen-presenting surface according to some embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This specification describes exemplary embodiments and applications of the disclosure. The disclosure, however, is not limited to these exemplary embodiments and applications or to the manner in which the exemplary embodiments and applications operate or are described herein. Moreover, the figures may show simplified or partial views, and the dimensions of elements in the figures may be exaggerated or otherwise not in proportion. In addition, as the terms “on,” “attached to,” “connected to,” “coupled to,” or similar words are used herein, one element (e.g., a material, a layer, a substrate, etc.) can be “on,” “attached to,” “connected to,” or “coupled to” another element regardless of whether the one element is directly on, attached to, connected to, or coupled to the other element or there are one or more intervening elements between the one element and the other element. Also, unless the context dictates otherwise, directions (e.g., above, below, top, bottom, side, up, down, under, over, upper, lower, horizontal, vertical, “x,” “y,” “z,” etc.), if provided, are relative and provided solely by way of example and for ease of illustration and discussion and not by way of limitation. In addition, where reference is made to a list of elements (e.g., elements a, b, c), such reference is intended to include any one of the listed elements by itself, any combination of less than all of the listed elements, and/or a combination of all of the listed elements. The term “or” is used in an inclusive sense, i.e., equivalent to “and/or,” unless the context dictates otherwise. It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” and any singular use of any word, include plural referents unless expressly and unequivocally limited to one referent. As used herein, the terms “comprise,” “include,” and grammatical variants thereof are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items. Section divisions in the specification are for ease of review only and do not limit any combination of elements discussed. In case of any contradiction or conflict between material incorporated by reference and the expressly described content provided herein, the expressly described content controls. 
     Where dimensions of microfluidic features are described as having a width or an area, the dimension typically is described relative to an x-axial and/or y-axial dimension, both of which lie within a plane that is parallel to the substrate and/or cover of the microfluidic device. The height of a microfluidic feature may be described relative to a z-axial direction, which is perpendicular to a plane that is parallel to the substrate and/or cover of the microfluidic device. In some instances, a cross sectional area of a microfluidic feature, such as a channel or a passageway, may be in reference to a x-axial/z-axial, a y-axial/z-axial, or an x-axial/y-axial area. 
     For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages, or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about,” to the extent they are not already so modified. “About” indicates a degree of variation that does not substantially affect the properties of the described subject matter, e.g., within 10%, 5%, 2%, or 1%. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed considering the number of reported significant digits and by applying ordinary rounding techniques. 
     Definitions 
     As used herein, “substantially” means sufficient to work for the intended purpose. The term “substantially” thus allows for minor, insignificant variations from an absolute or perfect state, dimension, measurement, result, or the like such as would be expected by a person of ordinary skill in the field but that do not appreciably affect overall performance. When used with respect to numerical values or parameters or characteristics that can be expressed as numerical values, “substantially” means within ten percent. 
     The term “ones” means more than one. As used herein, the term “plurality” can be 2, 3, 4, 5, 6, 7, 8, 9, 10, or more. 
     As used herein, “alkyl” refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, containing no unsaturation, having from one to six carbon atoms (e.g., C 1 -C 6  alkyl). Whenever it appears herein, a numerical range such as “1 to 6” refers to each integer in the given range; e.g., “1 to 6 carbon atoms” means that the alkyl group may consist of 1 carbon atom, 2 carbon atoms, 3 carbon atoms, etc., up to and including 6 carbon atoms, although the present definition also covers the occurrence of the term “alkyl” where no numerical range is designated. In some embodiments, it is a C 1 -C 3  alkyl group. Typical alkyl groups include, but are in no way limited to, methyl, ethyl, propyl, isopropyl, n-butyl, iso-butyl, sec-butyl isobutyl, tertiary butyl, pentyl, isopentyl, neopentyl, hexyl, and the like. The alkyl is attached to the rest of the molecule by a single bond, for example, methyl (Me), ethyl (Et), n-propyl, 1-methylethyl (iso-propyl), n-butyl, n-pentyl, 1,1-dimethylethyl (t-butyl); hexyl, and the like. 
     Unless stated otherwise specifically in the specification, an alkyl group may be optionally substituted by one or more substituents which independently are: aryl, arylalkyl, heteroaryl, heteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl, trifluoromethoxy, nitro, trimethylsilanyl, —OR′, —SR′, —OC(O)—R′, —C(O)R′, —C(O)OR′, —OC(O)N(R′) 2 , —C(O)N(R) 2 , —N(R′)C(O)OR′, —N(R′)C(O)R′, —N(R′)C(O)N(R′) 2 , N(R′)C(NR′)N(R′) 2 , —N(R′)S(O) t R′ (where t is 1 or 2), —S(O) t OR′ (where t is 1 or 2), —S(O) t N(R)2 (where t is 1 or 2), or PO 3 (R′) 2  where each R′ is independently hydrogen, alkyl, fluoroalkyl, aryl, aralkyl, heterocycloalkyl, or heteroaryl. 
     As referred to herein, a fluorinated alkyl moiety is an alkyl moiety having one or more hydrogens of the alkyl moiety replaced by a fluoro substituent. A perfluorinated alkyl moiety has all hydrogens attached to the alkyl moiety replaced by fluoro substituents. 
     As referred to herein, a “halo” moiety is a bromo, chloro, or fluoro moiety. 
     As referred to herein, an “olefinic” compound is an organic molecule which contains an “alkene” moiety. An alkene moiety refers to a group consisting of at least two carbon atoms and at least one carbon-carbon double bond. The non-alkene portion of the molecule may be any class of organic molecule, and in some embodiments, may include alkyl or fluorinated (including but not limited to perfluorinated) alkyl moieties, any of which may be further substituted. 
     As used herein, “air” refers to the composition of gases predominating in the atmosphere of the earth. The four most plentiful gases are nitrogen (typically present at a concentration of about 78% by volume, e.g., in a range from about 70-80%), oxygen (typically present at about 20.95% by volume at sea level, e.g. in a range from about 10% to about 25%), argon (typically present at about 1.0% by volume, e.g. in a range from about 0.1% to about 3%), and carbon dioxide (typically present at about 0.04%, e.g., in a range from about 0.01% to about 0.07%). Air may have other trace gases such as methane, nitrous oxide or ozone, trace pollutants and organic materials such as pollen, diesel particulates and the like. Air may include water vapor (typically present at about 0.25%, or may be present in a range from about 10 ppm to about 5% by volume). Air may be provided for use in culturing experiments as a filtered, controlled composition and may be conditioned as described herein. 
     As used herein, the term “plurality” can be 2, 3, 4, 5, 6, 7, 8, 9, 10, or more. 
     As used herein, the term “disposed” encompasses within its meaning “located.” 
     As used herein, a “microfluidic device” or “microfluidic apparatus” is a device that includes one or more discrete microfluidic circuits configured to hold a fluid, each microfluidic circuit comprised of fluidically interconnected circuit elements, including but not limited to region(s), flow path(s), channel(s), chamber(s), and/or pen(s), and at least one port configured to allow the fluid (and, optionally, micro-objects suspended in the fluid) to flow into and/or out of the microfluidic device. Typically, a microfluidic circuit of a microfluidic device will include a flow region, which may include a microfluidic channel, and at least one chamber, and will hold a volume of fluid of less than about 1 mL, e.g., less than about 750, 500, 250, 200, 150, 100, 75, 50, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, or 2 μL. In certain embodiments, the microfluidic circuit holds about 1-2, 1-3, 1-4, 1-5, 2-5, 2-8, 2-10, 2-12, 2-15, 2-20, 5-20, 5-30, 5-40, 5-50, 10-50, 10-75, 10-100, 20-100, 20-150, 20-200, 50-200, 50-250, or 50-300 μL. The microfluidic circuit may be configured to have a first end fluidically connected with a first port (e.g., an inlet) in the microfluidic device and a second end fluidically connected with a second port (e.g., an outlet) in the microfluidic device. 
     As used herein, a “nanofluidic device” or “nanofluidic apparatus” is a type of microfluidic device having a microfluidic circuit that contains at least one circuit element configured to hold a volume of fluid of less than about 1 μL, e.g., less than about 750, 500, 250, 200, 150, 100, 75, 50, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 nL or less. A nanofluidic device may comprise a plurality of circuit elements (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 75, 100, 150, 200, 250, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 6000, 7000, 8000, 9000, 10,000, or more). In certain embodiments, one or more (e.g., all) of the at least one circuit elements is configured to hold a volume of fluid of about 100 μL to 1 nL, 100 μL to 2 nL, 100 μL to 5 nL, 250 μL to 2 nL, 250 μL to 5 nL, 250 μL to 10 nL, 500 μL to 5 nL, 500 μL to 10 nL, 500 μL to 15 nL, 750 μL to 10 nL, 750 μL to 15 nL, 750 μL to 20 nL, 1 to 10 nL, 1 to 15 nL, 1 to 20 nL, 1 to 25 nL, or 1 to 50 nL. In other embodiments, one or more (e.g., all) of the at least one circuit elements are configured to hold a volume of fluid of about 20 nL to 200 nL, 100 to 200 nL, 100 to 300 nL, 100 to 400 nL, 100 to 500 nL, 200 to 300 nL, 200 to 400 nL, 200 to 500 nL, 200 to 600 nL, 200 to 700 nL, 250 to 400 nL, 250 to 500 nL, 250 to 600 nL, or 250 to 750 nL. 
     A microfluidic device or a nanofluidic device may be referred to herein as a “microfluidic chip” or a “chip”; or “nanofluidic chip” or “chip”. 
     A “microfluidic channel” or “flow channel” as used herein refers to flow region of a microfluidic device having a length that is significantly longer than both the horizontal and vertical dimensions. For example, the flow channel can be at least 5 times the length of either the horizontal or vertical dimension, e.g., at least 10 times the length, at least 25 times the length, at least 100 times the length, at least 200 times the length, at least 500 times the length, at least 1,000 times the length, at least 5,000 times the length, or longer. In some embodiments, the length of a flow channel is about 100,000 microns to about 500,000 microns, including any value therebetween. In some embodiments, the horizontal dimension is about 100 microns to about 1000 microns (e.g., about 150 to about 500 microns) and the vertical dimension is about 25 microns to about 200 microns, (e.g., from about 40 to about 150 microns). It is noted that a flow channel may have a variety of different spatial configurations in a microfluidic device, and thus is not restricted to a perfectly linear element. For example, a flow channel may be, or include one or more sections having, the following configurations: curve, bend, spiral, incline, decline, fork (e.g., multiple different flow paths), and any combination thereof. In addition, a flow channel may have different cross-sectional areas along its path, widening and constricting to provide a desired fluid flow therein. The flow channel may include valves, and the valves may be of any type known in the art of microfluidics. Examples of microfluidic channels that include valves are disclosed in U.S. Pat. Nos. 6,408,878 and 9,227,200, each of which is herein incorporated by reference in its entirety. 
     As used herein, the term “obstruction” refers generally to a bump or similar type of structure that is sufficiently large so as to partially (but not completely) impede movement of target micro-objects between two different regions or circuit elements in a microfluidic device. The two different regions/circuit elements can be, for example, a microfluidic sequestration pen and a microfluidic channel, or a connection region and an isolation region of a microfluidic sequestration pen. 
     As used herein, the term “constriction” refers generally to a narrowing of a width of a circuit element (or an interface between two circuit elements) in a microfluidic device. The constriction can be located, for example, at the interface between a microfluidic sequestration pen and a microfluidic channel, or at the interface between an isolation region and a connection region of a microfluidic sequestration pen. 
     As used herein, the term “transparent” refers to a material which allows visible light to pass through without substantially altering the light as is passes through. 
     As used herein, the term “micro-object” refers generally to any microscopic object that may be isolated and/or manipulated in accordance with the present disclosure. Non-limiting examples of micro-objects include: inanimate micro-objects such as microparticles; microbeads (e.g., polystyrene beads, Luminex™ beads, or the like); magnetic beads; microrods; microwires; quantum dots, and the like; biological micro-objects such as cells; biological organelles; vesicles, or complexes; synthetic vesicles; liposomes (e.g., synthetic or derived from membrane preparations); lipid nanorafts, and the like; or a combination of inanimate micro-objects and biological micro-objects (e.g., microbeads attached to cells, liposome-coated micro-beads, liposome-coated magnetic beads, or the like). Beads may include moieties/molecules covalently or non-covalently attached, such as fluorescent labels, proteins, carbohydrates, antigens, small molecule signaling moieties, or other chemical/biological species capable of use in an assay. Lipid nanorafts have been described, for example, in Ritchie et al. (2009) “Reconstitution of Membrane Proteins in Phospholipid Bilayer Nanodiscs,” Methods Enzymol., 464:211-231. 
     As used herein, the term “cell” is used interchangeably with the term “biological cell.” Non-limiting examples of biological cells include eukaryotic cells, plant cells, animal cells, such as mammalian cells, reptilian cells, avian cells, fish cells, or the like, prokaryotic cells, bacterial cells, fungal cells, protozoan cells, or the like, cells dissociated from a tissue, such as muscle, cartilage, fat, skin, liver, lung, neural tissue, and the like, immunological cells, such as T cells, B cells, natural killer cells, macrophages, and the like, embryos (e.g., zygotes), oocytes, ova, sperm cells, hybridomas, cultured cells, cells from a cell line, cancer cells, infected cells, transfected and/or transformed cells, reporter cells, and the like. A mammalian cell can be, for example, from a human, a mouse, a rat, a horse, a goat, a sheep, a cow, a primate, or the like. 
     A colony of biological cells is “clonal” if all of the living cells in the colony that are capable of reproducing are daughter cells derived from a single parent cell. In certain embodiments, all the daughter cells in a clonal colony are derived from the single parent cell by no more than 10 divisions. In other embodiments, all the daughter cells in a clonal colony are derived from the single parent cell by no more than 14 divisions. In other embodiments, all the daughter cells in a clonal colony are derived from the single parent cell by no more than 17 divisions. In other embodiments, all the daughter cells in a clonal colony are derived from the single parent cell by no more than 20 divisions. The term “clonal cells” refers to cells of the same clonal colony. 
     As used herein, a “colony” of biological cells refers to 2 or more cells (e.g. about 2 to about 20, about 4 to about 40, about 6 to about 60, about 8 to about 80, about 10 to about 100, about 20 to about 200, about 40 to about 400, about 60 to about 600, about 80 to about 800, about 100 to about 1000, or greater than 1000 cells). 
     As used herein, the term “maintaining (a) cell(s)” refers to providing an environment comprising both fluidic and gaseous components and, optionally a surface, that provides the conditions necessary to keep the cells viable and/or expanding. 
     As used herein, the term “expanding” when referring to cells, refers to increasing in cell number. 
     As referred to herein, “gas permeable” means that the material or structure is permeable to at least one of oxygen, carbon dioxide, or nitrogen. In some embodiments, the gas permeable material or structure is permeable to more than one of oxygen, carbon dioxide and nitrogen and may further be permeable to all three of these gases. 
     A “component” of a fluidic medium is any chemical or biochemical molecule present in the medium, including solvent molecules, ions, small molecules, antibiotics, nucleotides and nucleosides, nucleic acids, amino acids, peptides, proteins, sugars, carbohydrates, lipids, fatty acids, cholesterol, metabolites, or the like. 
     As used herein in reference to a fluidic medium, “diffuse” and “diffusion” refer to thermodynamic movement of a component of the fluidic medium down a concentration gradient. 
     The phrase “flow of a medium” means bulk movement of a fluidic medium primarily due to any mechanism other than diffusion. For example, flow of a medium can involve movement of the fluidic medium from one point to another point due to a pressure differential between the points. Such flow can include a continuous, pulsed, periodic, random, intermittent, or reciprocating flow of the liquid, or any combination thereof. When one fluidic medium flows into another fluidic medium, turbulence and mixing of the media can result. 
     The phrase “substantially no flow” refers to a rate of flow of a fluidic medium that, when averaged over time, is less than the rate of diffusion of components of a material (e.g., an analyte of interest) into or within the fluidic medium. The rate of diffusion of components of such a material can depend on, for example, temperature, the size of the components, and the strength of interactions between the components and the fluidic medium. 
     As used herein in reference to different regions within a microfluidic device, the phrase “fluidically connected” means that, when the different regions are substantially filled with fluid, such as fluidic media, the fluid in each of the regions is connected so as to form a single body of fluid. This does not mean that the fluids (or fluidic media) in the different regions are necessarily identical in composition. Rather, the fluids in different fluidically connected regions of a microfluidic device can have different compositions (e.g., different concentrations of solutes, such as proteins, carbohydrates, ions, or other molecules) which are in flux as solutes move down their respective concentration gradients and/or fluids flow through the device. 
     As used herein, a “flow path” refers to one or more fluidically connected circuit elements (e.g. channel(s), region(s), chamber(s) and the like) that define, and are subject to, the trajectory of a flow of medium. A flow path is thus an example of a swept region of a microfluidic device. Other circuit elements (e.g., unswept regions) may be fluidically connected with the circuit elements that comprise the flow path without being subject to the flow of medium in the flow path. 
     As used herein, “isolating a micro-object” confines a micro-object to a defined area within the microfluidic device. 
     A microfluidic (or nanofluidic) device can comprise “swept” regions and “unswept” regions. As used herein, a “swept” region is comprised of one or more fluidically interconnected circuit elements of a microfluidic circuit, each of which experiences a flow of medium when fluid is flowing through the microfluidic circuit. The circuit elements of a swept region can include, for example, regions, channels, and all or parts of chambers. As used herein, an “unswept” region is comprised of one or more fluidically interconnected circuit element of a microfluidic circuit, each of which experiences substantially no flux of fluid when fluid is flowing through the microfluidic circuit. An unswept region can be fluidically connected to a swept region, provided the fluidic connections are structured to enable diffusion but substantially no flow of media between the swept region and the unswept region. The microfluidic device can thus be structured to substantially isolate an unswept region from a flow of medium in a swept region, while enabling substantially only diffusive fluidic communication between the swept region and the unswept region. For example, a flow channel of a micro-fluidic device is an example of a swept region while an isolation region (described in further detail below) of a microfluidic device is an example of an unswept region. 
     As used herein, a “non-sweeping” rate of fluidic medium flow means a rate of flow in a flow region, such as a microfluidic channel, which is sufficient to permit components of a second fluidic medium in an isolation region of the sequestration pen to diffuse into the first fluidic medium in the flow region and/or components of the first fluidic medium to diffuse into the second fluidic medium in the isolation region; and further wherein the first medium does not substantially flow into the isolation region. 
     As used herein, “synthetic surface” refers to an interface between a support structure and a gaseous/liquid medium, where the synthetic surface is prepared by non-biological processes. The synthetic surface may have biologically derived materials connected to it, e.g., primary and co-activating molecules as described herein, to provide an antigen-presenting synthetic surface, provided that the synthetic surface is not expressed by a biological organism. Typically, the support structure is solid, such as the non-surface exposed portions of a bead, a wafer, or a substrate, cover or circuit material of a microfluidic device and does not enclose a biological nucleus or organelle. 
     As used herein, “co-activating” refers to a binding interaction between a biological macromolecule, fragment thereof, or synthetic or modified version thereof and a T cell, other than the primary T cell receptor/antigen:MHC binding interaction, that enhances a productive immune response to produce activation of the T cell. Co-activating interactions are antigen-nonspecific interactions, e.g., between a T-cell surface protein able to engage in intracellular signaling such as CD28, CD2, ICOS, etc., and an agonist thereof. “Co-activation” and “co-activating” as used herein is equivalent to the terms co-stimulation and co-stimulating, respectively. 
     As used herein, a “TCR co-activating molecule” is a biological macromolecule, fragment thereof, or synthetic or modified version thereof that binds to one or more co-receptors on a T Cell that activate distal signaling molecules which amplify and/or complete the response instigated by antigen specific binding of the TCR. In one example, signaling molecules such as transcription factors Nuclear Factor kappa B (NF kB) and Nuclear factor of activated T cells (NFAT) are activated by the TCR co-activating molecule. The TCR co-activating molecule can be, for example, an agonist of the CD28 receptor, which signals through the phosphoinositide 3 kinase (PI3K)/Akt pathway. See  FIG. 4 . 
     As used herein, “CD28high” refers to a phenotype of high CD28 surface expression in a T cell. Those skilled in the art are familiar with the CD28high phenotype and appropriate ways of identifying CD28high T cells. Unless otherwise indicated, CD28high T cells include T cells that meet any of the following criteria. In some embodiments, a CD28high T cell is a T cell that expresses higher levels of CD28 than a resting CD8+ T cell. A CD28high T cell may also express higher levels of CD28 than an irrelevant non-antigen specific T cell. In some embodiments, CD28high T cells are a population in which the level of surface CD28 which can be measured by FACS is equal to or greater than the level of surface CD28 present on circulating memory T cells which can be measured by FACS. In some embodiments, a CD28high T cell has a level of surface CD28 equal to or greater than the level of surface CD28 present on circulating memory T cells from the same sample or individual. Expression of surface CD28 can be determined by FACS and the mean (e.g., geometric mean) or median level of surface CD28 present on circulating memory T cells can be used for determining whether a given T cell is CD28high. In some embodiments, a CD28high T cell is a T cell that expresses CD28 at a significantly higher level than expression typical of naïve CD8 T cells from the same sample or individual, e.g., higher than 75%, 80%, 85%, 87.5%, 90%, 92.5%, or 95% of the naïve T cells. Naïve CD8 T cells can be identified and characterized by known methods, e.g., flow cytometrically, as CD8+ cells expressing detectable CD28 and minimal or no CD45RO. 
     As used herein, a “TCR adjunct activating molecule” stimulates classes of signaling molecules which amplify the antigen-specific TCR interaction and are distinct from the TCR co-activating molecules. For example, TCR proximal signaling by phosphorylation of the TCR proximal signaling complex is one route by which TCR adjunct activating molecules can act. The TCR adjunct activating molecule may be, for example, an agonist of the CD2 receptor. See  FIG. 4 . 
     As used herein, an “activated T cell” is a T cell that has experienced antigen (or a descendant thereof) and is capable of mounting an antigen-specific response to that antigen. Activated T cells are generally positive for at least one of CD28, CD45RO, CD127, and CD197. 
     Overview. 
     Immunotherapy for cancer is a promising development, but requires specifically activated T lymphocytes which are compatible with the subject of the therapy. However, the current use of antigen presenting dendritic cells to activate T lymphocytes presents several disadvantageous aspects. Dendritic cells must be obtained from donor sources, limiting throughput. Dendritic cells must be matured for each sequence of T lymphocyte activation, which requires a lead time of about 7 days. Irradiation of dendritic cells is also required, which limits where such processing can be performed. 
     Replacing the use of autologous antigen presenting dendritic cells with antigen presenting synthetic surfaces for activating T lymphocytes may afford greater reproducibility to stimulate and expand T lymphocytes for a therapeutically relevant population. Antigen presenting synthetic surfaces may be engineered for antigen-specific activation of T lymphocytes, providing more controllable, characterizable, reproducible and/or more rapid development of populations of activated T lymphocytes having desirable phenotypes for treatment of cancer. Antigen-presenting synthetic surfaces can also allow for more control and selectivity over T cell activation, including more precise targeting of desired T cell phenotypes following activation, e.g., enrichment of particular forms of memory T cells. Furthermore, antigen-presenting synthetic surfaces can also exploit economies of scale and/or provide reproducibility to a greater degree than using autologous antigen presenting dendritic cells. As such, this technology can make cellular therapies available to patients in need thereof in greater numbers and/or in less time. Providing T cells useful for cellular therapies more rapidly can be especially important for patients with advanced disease. The structure of such antigen-presenting synthetic surfaces and their methods of preparation and use are described herein. In some embodiments, the antigen-presenting synthetic surfaces comprise primary activating ligands in combination with TCR co-activating molecules and/or adjunct TCR activating molecules, which together serve to activate T cells. Surface density ranges for these components and ratios of one to another that can further improve efficacy are also disclosed herein. In some embodiments, the antigen-presenting synthetic surfaces and their methods of preparation and use provide one or more of the foregoing advantages, or at least provide the public with a useful choice. 
     Antigen-Presenting Synthetic Surface for T Cell Activation. 
     An antigen-presenting synthetic surface is provided herein for activating a T lymphocyte (T cell) comprising: a plurality of primary activating molecular ligands, and a plurality of co-activating molecular ligands each comprising a T cell receptor (TCR) co-activating molecule or an adjunct TCR activating molecule, wherein each of the plurality of primary activating molecular ligands and the plurality of co-activating molecular ligands is specifically bound to the antigen presenting synthetic surface. Each primary activating molecular ligand can comprise a major histocompatibility complex (MHC) molecule configured to bind to a T cell receptor of the T cell. In some embodiments, the MHC molecule is an MHC Class 1 molecule. In some other embodiments, the MHC molecule is an MHC Class II molecule. In some embodiments, the primary activating molecular ligand comprises an antigenic peptide (e.g., covalently or non-covalently bound to an MHC molecule). In some embodiments, the plurality of co-activating molecular ligands comprises a plurality of T cell receptor (TCR) co-activating molecules and a plurality of adjunct TCR activating molecules. In some embodiments, the T cell receptor (TCR) co-activating molecules and the adjunct TCR activating molecules are present in a ratio of about 1:100 to about 100:1, e.g., about 20:1 to about 1:20, or about 10:1 to about 1:20. In some embodiments, one or more of the plurality of co-activating molecular ligands is a TCR co-activating molecule which can activate signaling molecules such as transcription factors Nuclear Factor kappa B (NF kB) and Nuclear factor of activated T cells (NFAT). In some embodiments, the TCR co-activating molecule is an agonist of the CD28 receptor, which signals through the phosphoinositide 3 kinase (PI3K)/Akt pathway. In some embodiments, one or more of the plurality of co-activating molecular ligands is a TCR adjunct activating molecule which activates TCR proximal signaling, e.g., by phosphorylation of the TCR proximal signaling complex. The TCR adjunct activating molecule may be, for example, an agonist of the CD2 receptor. Exemplary pathways that can be activated through the CD28 and CD2 receptors (and additional details) are shown in  FIG. 4 . The T cell activated by this antigen-presenting synthetic surface may be a naïve T cell. The antigen-presenting synthetic surface may be an antigen-presenting bead, antigen-presenting wafer, an antigen-presenting inner surface of a tube (e.g., glass or polymer tube), or an antigen-presenting inner surface of a microfluidic device. The antigen-presenting microfluidic device may be any microfluidic device as described herein, and may have any combination of features described herein. 
     In various embodiments, the antigen-presenting synthetic surface is configured to activate a T lymphocyte in vitro. The primary activating molecular ligand may comprise a MHC molecule having an amino acid sequence and may be connected covalently to the surface of the antigen-presenting synthetic surface via a C-terminal connection. The MHC molecule may present a N-terminal portion of the MHC molecule oriented away from the surface, thereby facilitating specific binding of the MHC molecule with the TCR of a T lymphocyte disposed upon the surface. The MHC molecule may include a MHC peptide. Clusters of at least four of the MHC molecules may be disposed at locations upon the antigen-presenting synthetic surface such that when the surface is exposed to an aqueous environment, a MHC tetramer may be formed. 
     In some embodiments, each of the plurality of primary activating molecular ligands may be covalently connected to the antigen presenting synthetic surface via a linker. In some embodiments, an MHC molecule of a primary activating molecular ligand may be connected to the antigen-presenting synthetic surface through a covalent linkage. Covalent linkages can be formed, for example, using Click chemistry and an appropriate Click reagent pair. Likewise, other ligands described herein, such as co-activating molecular ligands (comprising TCR co-activating molecules and/or adjunct TCR activating molecules), growth stimulatory molecular ligands, and additional stimulatory molecular ligands may be covalently connected to the surface of the antigen presenting synthetic surface via a linker, and the linkage can be formed using Click chemistry and an appropriate Click reagent pair. 
     In other embodiments, the MHC molecule may be connected to the antigen presenting synthetic surface noncovalently through a coupling group (CG), such as a biotin/streptavidin binding pair interaction. In some embodiments, one member of the coupling group is covalently associated with the surface (e.g., streptavidin). Further examples of coupling groups include, but are not limited to biotin/avidin, biotin/NeutrAvidin, and digoxygenin/anti-digoxygenin. Streptavidin, avidin, and NeutrAvidin represent examples of biotin-binding agents. Likewise, other ligands described herein, such as co-activating molecular ligands (comprising TCR co-activating molecules and/or adjunct TCR activating molecules), growth stimulatory molecular ligands, and additional stimulatory molecular ligands may be noncovalently coupled to the antigen presenting synthetic surface, and the coupling group may include biotin or digoxygenin. 
     In some embodiments, one member of the CG binding pair may itself be covalently bound to the surface, e.g., through one or more linkers. The covalent linkange to the surface can be through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetwteen. In some embodiments, the member of the CG binding pair covalently bound to the surface is bound through a Click reagent pair. This may also be true for CG binding pair members involved in associating other ligands described herein (such as co-activating molecular ligands, TCR co-activating molecules, adjunct TCR activating molecules, growth stimulatory molecules, and additional stimulatory molecules) with the surface. Further, since some binding pair members such as streptavidin have multiple binding sites (e.g., four in streptavidin), a primary activating molecular ligand may be coupled to the antigen presenting synthetic surface by a biotin/streptavidin/biotin linkage. Again, this may also be true for CG binding pair members involved in associating other ligands described herein (such as co-activating molecular ligands, TCR co-activating molecules, adjunct TCR activating molecules, growth stimulatory molecules, and additional stimulatory molecules) with the surface. 
     In some embodiments, a first member of the CG binding pair is covalently associated with the primary activating molecular ligand and a second member of the CG binding pair is non-covalently associated with the surface. For example, the first member of the CG binding pair can be a biotin covalently associated with the primary activating molecular ligand; and the second member of the CG binding pair can be a streptavidin non-covalently associated with the surface (e.g., through an additional biotin, wherein the additional biotin is covalently associated with the surface). In some embodiments, the biotin covalently associated with the surface is linked to the surface through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetwteen. For example, the biotin covalently associated with the surface may be linked to the surface through a series of one or more linkers having a total length as described. Again, this may also be true for CG binding pair members involved in associating other ligands described herein (such as co-activating molecular ligands, TCR co-activating molecules, adjunct TCR activating molecules, growth stimulatory molecules, and additional stimulatory molecules) with the surface. Noncovalently associating the second member of the CG binding pair, such as streptavidin, with the surface may facilitate loading ligands such as primary activating molecular ligands, co-activating molecular ligands, TCR co-activating molecules, and adjunct TCR activating molecules at greater densities than if the second member of the CG binding pair is covalently associated with the surface. 
     The primary activating molecular ligand (e.g., comprising a MHC molecule) may further include an antigenic peptide that comprises a tumor associated antigen. The tumor associated antigen may be noncovalently associated with the primary activating molecular ligand (e.g., MHC molecule). The tumor associated antigen may be presented by the primary activating molecular ligand (e.g., MHC molecule) in an orientation which can initiate activation of a T lymphocyte. The tumor associated antigen may be a peptide. Some non-limiting examples of tumor associated antigens include MART1 (peptide sequence ELAGIGILTV), for melanoma, NYESO1 (peptide sequence SLLMWITQV), involved in melanoma and some carcinomas, SLC45A2, TCL1, and VCX3A, but the disclosure is not so limited. Additional examples of tumor antigens include peptides comprising a segment of amino acid sequence from a protein expressed on the surface of a tumor cell such as CD19, CD20, CLL-1, TRP-2, LAGE-1, HER2, EphA2, FOLR1, MAGE-A1, mesothelin, SOX2, PSM, CA125, T antigen, etc. The peptide can be from an extracellular domain of the tumor associated antigen. An antigen is considered tumor associated if it is expressed at a higher level on a tumor cell than on a healthy cell of the type from which the tumor cell was derived. The T cell which recognizes this tumor associated antigen is an antigen specific T cell. Any tumor associated antigen may be utilized in the antigen presenting surface described herein. In some embodiments, the tumor associated antigen is a neoantigenic peptide, e.g., encoded by a mutant gene in a tumor cell. For detailed discussion of neoantigenic peptides, see, e.g., US 2011/0293637. 
     The antigen presenting synthetic surface includes a plurality of co-activating molecular ligands each comprising a TCR co-activating molecule or an adjunct TCR activating molecule. In some embodiments, the plurality of co-activating molecular ligands include a plurality of TCR co-activating molecules. In some embodiments, the plurality of co-activating molecular ligands include a plurality of adjunct TCE activating molecules. In other embodiments, the plurality of co-activating molecular ligands may include TCR co-activating molecules and adjunct TCR activating molecules. The TCR co-activating molecules and the adjunct TCR activating molecules can be present in a ratio of one to the other such as 100:1 to 1:100, 10:1 to 1:20, 5:1 to 1:5, 3:1 to 1:3, 2:1 to 1:2, or the like, wherein each of the foregoing values can be modified by “about.” In some embodiments, the plurality of co-activating molecular ligands may include TCR co-activating molecules and adjunct TCR activating molecules in a ratio ranging from about 3:1 to about 1:3. 
     The TCR co-activating molecule or adjunct TCR activating molecule may include a protein, e.g., an antibody or a fragment thereof. In some embodiments, the TCR co-activating molecule may be a CD28 binding molecule (e.g., including a CD80 molecule) or a fragment thereof which retains binding ability to CD28. In some embodiments, the TCR co-activating molecule may be a CD28 binding molecule (e.g., including a CD80 molecule) or a fragment thereof which specifically binds to CD28. In some embodiments, the TCR co-activating molecule may be a CD28 binding molecule (e.g., including a CD80 molecule) or a CD28-binding fragment thereof. In some embodiments, the TCR co-activating molecule may include an anti-CD28 antibody or a fragment thereof (e.g., a CD28-binding fragment). 
     In some embodiments, each of the plurality of co-activating molecular ligands may be covalently connected to the antigen-presenting synthetic surface via a linker. In other embodiments, each of the plurality of co-activating molecular ligands may be noncovalently bound to a linker covalently bound to the antigen-presenting synthetic surface. The TCR co-activating molecule or adjunct TCR activating molecule may be connected to the covalently modified surface noncovalently through a CG, such as a biotin/streptavidin binding pair interaction. For example, the TCR co-activating molecule or adjunct TCR activating molecule may further comprise a site-specific C-terminal biotin moiety that interacts with a streptavidin, which may be associated covalently or noncovalently with the surface as described herein. A site-specific C-terminal biotin moiety can be added to a TCR co-activating molecule or adjunct TCR activating molecule using known methods, e.g., using a biotin ligase such as the BirA enzyme. See, e.g., Fairhead et al., Methods Mol Biol 1266:171-184, 2015. Further examples of coupling groups include biotin/avidin, biotin/NeutrAvidin, and digoxygenin/anti-digoxygenin. In some embodiments, one of the CG binding pair may itself be covalently bound to the surface, e.g., through a linker, as described above. See the examples for exemplary TCR co-activating molecules or adjunct TCR activating molecules. 
     In some other embodiments, the co-activating molecular ligands of the antigen-presenting synthetic surface may include a plurality of adjunct TCR activating molecules, e.g., in addition to or instead of a TCR co-activating molecule as described herein. In some further embodiments, there may be additional co-activating molecular ligands. In some embodiments, the adjunct TCR activating molecules or additional co-activating molecular ligands comprise one or more of a CD2 agonist, a CD27 agonist, or a CD137 agonist. For example, the adjunct TCR activating molecule may be a CD2 binding protein or a fragment thereof, where the fragment retains binding ability with CD2. In some embodiments, the adjunct TCR activating molecule may be CD58 or a fragment thereof which retains binding ability with CD2. The adjunct TCR activating molecule may be a CD2 binding protein (e.g., CD58) or a fragment thereof, where the fragment specifically binds CD2. The adjunct TCR activating molecule may be a CD2 binding protein (e.g., CD58) or a CD2-binding fragment thereof. The adjunct TCR activating molecules or additional co-activating molecular ligands may each be an antibody to CD2, CD27, or CD137, or there may be any combination of such antibodies. The adjunct TCR activating molecules or additional co-activating molecular ligands may alternatively each be a fragment of an antibody to CD2, CD27, or CD137, or any combination thereof. Varlilumab (CDX-1127) is an exemplary anti-CD27 antibody. Utomilumab (PF-05082566) is an exemplary anti-CD137 antibody. CD70 or an extracellular portion thereof may also be used as a CD27 agonist. TNFSF9, also known as CD137L, or an extracellular portion thereof may also be used as a CD137 agonist. In some embodiments, the adjunct TCR activating molecules comprise an agonist of CD2, such as an anti-CD2 antibody. In some embodiments, each of the adjunct TCR activating molecules may be covalently connected to the surface via a linker. In other embodiments, each of the adjunct TCR activating molecules may be noncovalently bound to a linker covalently bound to the surface, e.g., through a CG, such as a biotin/streptavidin binding pair interaction. For example, the adjunct TCR activating molecules may comprise a site-specific C-terminal biotin moiety as discussed above that interacts with a streptavidin, which may be associated covalently or noncovalently with the surface as described herein. Further examples of coupling groups include biotin/avidin, biotin/NeutrAvidin, and digoxygenin/anti-digoxygenin. In some embodiments, one of the CG binding pair may itself be covalently bound to the surface, e.g., through a linker. 
     The antigen-presenting synthetic surface may further include at least one growth stimulatory molecular ligand. The growth stimulatory molecular ligand may be a protein or peptide. The growth stimulatory protein or peptide may be a cytokine or fragment thereof. The growth stimulatory protein or peptide may be a growth factor receptor ligand. The growth stimulatory molecular ligand may comprise IL-21 or a fragment thereof. In some embodiments, the growth stimulatory molecular ligand may be connected to the antigen-presenting synthetic surface via a covalent linker. In other embodiments, the growth stimulatory molecular ligand may be connected to the antigen-presenting synthetic surface through a CG, such as a biotin/streptavidin binding pair interaction. Further examples of coupling groups include biotin/avidin, biotin/NeutrAvidin, and digoxygenin/anti-digoxygenin. In some embodiments, one of the CG binding pair may itself be covalently bound to the surface, e.g., through a linker. In other embodiments, the growth stimulatory molecular ligand may be attached to a surface either covalently or via a biotin/streptavidin binding interaction, where the surface is not the same surface as the antigen-presenting synthetic surface having MHC molecules connected thereto. For example, the surface to which the growth stimulatory molecular ligand is attached can be a second surface of a microfluidic device also comprising a first, antigen-presenting synthetic surface. 
     In yet other embodiments, there may be additional growth stimulatory molecular ligands, which may be one or more cytokines, or fragments thereof. In some embodiments, additional stimulatory molecular ligands including, but not limited to IL-2 or IL-7 may be connected to a the antigen-presenting synthetic surface or to another surface that is not the antigen-presenting synthetic surface, as discussed above with respect to growth stimulatory molecular ligands. 
     In some embodiments, the antigen-presenting synthetic surface comprises an adhesion stimulatory molecular ligand, which is a ligand for a cell adhesion receptor including an ICAM protein sequence. 
     The additional stimulatory molecular ligands and/or adhesion stimulatory molecular ligands may be covalently connected to a surface or may be noncovalently connected to a surface through a CG, such as a biotin/streptavidin binding pair interaction. Further examples of coupling groups include biotin/avidin, biotin/NeutrAvidin, and digoxygenin/anti-digoxygenin. In some embodiments, one of the CG binding pair may itself be covalently bound to the surface, e.g., through a linker via a biotin/streptavidin binding interaction. 
     In some embodiments, the antigen-presenting synthetic surface comprises a plurality of surface-blocking molecular ligands, which may include a linker and a terminal surface-blocking group. The linker can include a linear chain of 6 or more atoms (e.g., 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100, or more atoms) covalently linked together. Optionally, the linker has a linear structure. The terminal surface-blocking group may be a hydrophilic moiety, an amphiphilic moiety, a zwitterionic moiety, or a negatively charged moiety. In some embodiments, the terminal blocking group comprises a terminal hydroxyl group. In some embodiments, the terminal blocking group comprises a terminal carboxyl group. In some embodiments, the terminal blocking group comprises a terminal zwitterionic group. The plurality of surface-blocking molecular ligands may have all the same terminal surface-blocking group or may have a mixture of terminal surface-blocking groups. Without being bound by theory, the terminal surface-blocking group as well as a hydrophilic linker of the surface-blocking molecular ligand may interact with water molecules in the aqueous media surrounding the antigen-presenting synthetic surface to create a more hydrophilic surface overall. This enhanced hydrophilic nature may render the contact between the antigen-presenting synthetic surface and a cell more compatible and more similar to natural intercellular interactions and/or cell-extracellular fluidic environment in-vivo. The linker can comprise, for example, a polymer. The polymer may include a polymer including alkylene ether moieties. A wide variety of alkylene ether containing polymers may be suitable for use on the surfaces described herein. One class of alkylene ether containing polymers is polyethylene glycol (PEG M w &lt;100,000 Da), which are known in the art to be biocompatible. In some embodiments, a PEG may have an M w  of about 88 Da, 100 Da, 132 Da, 176 Da, 200 Da, 220 Da, 264 Da, 308 Da, 352 Da, 396 Da, 440 Da, 500 Da, 600 Da, 700 Da, 800 Da, 900 Da, 1000 Da, 1500 Da, 2000 Da, 5000 Da, 10,000 Da or 20,000 Da, or may have a M w  that falls within a range defined by any two of the foregoing values. In some embodiments, the PEG polymer has a polyethylene moiety repeat of about 3, 4, 5, 10, 15, 25 units, or any value therebetween. In some embodiments, the PEG is a carboxyl substituted PEG moiety. In some embodiments, the PEG is a hydroxyl substituted PEG moiety. In some embodiments, each of the plurality of surface-blocking molecular ligands may have a linker having the same length as the linkers of the other ligands of the plurality. In other embodiments, the linkers of the plurality of surface-blocking molecular ligands may have varied lengths. In some embodiments, the surface-blocking group and the length of the linker may be same for each of the plurality of surface-blocking molecular ligands. Alternatively, the surface blocking group and the length of the linker may vary within the plurality of the surface-blocking molecular ligands and may include 2, 3, or 4 different surface-blocking groups and/or 2, 3, 4, or more different lengths, chosen in any combination. In general, the surface-blocking molecular ligands have a length and/or structure that is sufficiently short so as not to sterically hinder the binding and/or function of the primary activating molecular ligands and the co-activating molecular ligands. For example, in some embodiments, the length of the surface-blocking molecular ligands is equal to or less than the length of the other linkers bound to the surface (e.g., linkers that connect coupling groups, primary activating molecular ligands, co-stimulating molecular ligands, or other ligands). In some embodiments, the length of the surface-blocking molecular ligands is about 1 or more angstroms (e.g., about 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100, or more angstroms) less than the length of the other linkers bound to the surface (e.g., linkers that connect coupling groups, primary activating molecular ligands, co-stimulating molecular ligands, or other ligands). In some embodiments, the length of the surface-blocking molecular ligands is about 1 to about 100 angstroms (e.g., about 2 to about 75, about 3 to about 50, about 4 to about 40, or about 5 to about 30 angstroms) less than the length of the other linkers bound to the surface. When the surface-blocking molecular ligands have a length that is the same or somewhat less than the length of the other linkers bound to the surface, the resulting surface effectively presents the ligands attached to the other linkers in a manner that is readily available for coupling and/or interacting with cells. With respect to antigen-presenting beads, it has been found that including a surface-blocking molecular ligand such as a hydrophilic polymer, e.g., a PEG or PEO polymer and/or ligands comprising terminal hydroxyl or carboxyl groups, can beneficially reduce aggregation of the beads through hydrophobic interactions. The surface-blocking molecular ligands can be attached to the surface after the primary and other (e.g., coactivating, adjunct, etc.) ligands discussed above or may be introduced before any of the activating or co-activating species are attached to the surface, as set forth in any embodiments disclosed herein. 
     The antigen-presenting synthetic surface may comprise glass, metal, a polymer, or a metal oxide. In some embodiments, the antigen-presenting synthetic surface is a surface of a wafer having any kind of configuration, a surface of a bead, at least one inner surface of a fluidic circuit containing device (e.g., microfluidic device) configured to contain a plurality of cells, or an inner surface of a tube (e.g., glass or polymer tube). In some embodiments, the wafer having a antigen-presenting synthetic surface configured to activate T lymphocytes may be sized to fit within a well of a standard 48, 96 or 384 wellplate. In various embodiments, beads having a antigen-presenting synthetic surface configured to activate T lymphocytes may be disposed for use within a wellplate or within a fluidic circuit containing device. In some embodiments, the density of the plurality of primary activating molecular ligands on the antigen-presenting synthetic surface (or in each portion or sub-region where it is attached) may be from about 50 to about 500 molecules per square micron; about 4×10 2  to about 2×10 3  molecules per square micron; about 1×10 3  to about 2×10 4  molecules per square micron; about 5×10 3  to about 3×10 4  molecules per square micron; about 4×10 2  to about 3×10 4  molecules per square micron; about 4×10 2  to about 2×10 3  molecules per square micron; about 2×10 3  to about 5×10 3  molecules per square micron; about 5×10 3  to about 2×10 4  molecules per square micron; about 1×10 4  to about 2×10 4  molecules per square micron; or about 1.25×10 4  to about 1.75×10 4  molecules per square micron. 
     In some embodiments, the density of the plurality of co-activating molecular ligands on the antigen-presenting synthetic surface (or in each portion or sub-region where it is attached) is from about 20 to about 250 molecules per square micron; about 2×10 2  to about 1×10 3  molecules per square micron; about 500 to about 5×10 3  molecules per square micron; about 1×10 3  to about 1×10 4  molecules per square micron; about 5×10 2  to about 2×10 4  molecules per square micron; about 5×10 2  to about 1.5×10 4  molecules per square micron; about 5×10 3  to about 2×10 4  molecules per square micron, about 5×10 3  to about 1.5×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  per square micron, about 1×10 4  to about 1.5×10 4  per square micron, about 1.25×10 4  to about 1.75×10 4 , or about 1.25×10 4  to about 1.5×10 4  per square micron. 
     Without wishing to be bound by any particular theory, certain experiments have indicated that it may be advantageous to provide and use beads for T cell activation that have relatively defined surface-area to volume ratios. Such beads may present the relevant ligands in a more accessible way so that they interact more efficiently with T cells during activation. Such beads may provide a desired degree of T cell activation with fewer ligands needed than beads with higher surface-area to volume ratios and/or may provide a higher degree of T cell activation or more T cells with desired features (e.g., antigen specificity and/or marker phenotypes described herein) than beads with higher surface-area to volume ratios. An ideally spherical solid has the lowest possible surface-area to volume ratio. Accordingly, in some embodiments, the bead surface-area is within 10% of the surface-area of a sphere of an equal size (volume or diameter), and is referred to herein as “substantially spherical.” For example, for a bead with a 2.8 μm diameter (1.4 μm radius), the corresponding ideal sphere would have a surface area of 4πr 2 =24.63 μm 2 . A substantially spherical 2.8 μm diameter bead with a surface-area within 10% of the surface-area of an ideal sphere of an equal volume or diameter would therefore have a surface-area less than or equal to 27.093 μm 2 . It is noted that certain commercially available beads are reported as having higher surface areas; for example, Dynabeads M-270 Epoxy are described in their product literature as having a specific surface area of 2-5 m 2 /g and a 2.8 μm diameter, and the literature also indicates that 1 mg of beads is 6-7×10 7  beads. Multiplying the specific surface area by 1 mg/6-7×10 7  beads gives a surface area per bead of 28 to 83 μm 2  per bead, which is more than 10% greater than the surface-area of an ideal sphere with a 2.8 μm diameter. Polymer beads having a surface area more than 10% greater than the surface-area of an ideal sphere are referred to herein as a “convoluted bead.” In some embodiments, a polymer bead may be either substantially spherical or convoluted. In some embodiments, the polymer bead is not convoluted, but is substantially spherical. 
     Unpatterned Surface. 
     In various embodiments, the antigen-presenting synthetic surface may be a unpatterned surface having a plurality of primary activating molecular ligands distributed evenly thereon. The primary activating molecular ligands can comprise MHC molecules, each of which may include a tumor associated antigen. The unpatterned surface may further include a plurality of co-activating molecular ligands (e.g., TCR co-activating molecules and/or adjunct TCR activating molecules) distributed evenly thereon. The co-activating molecular ligands may be as described above for antigen-presenting surfaces, in any combination. The density of the primary activating molecular ligands and the co-activating molecular ligands may the same ranges as described above for antigen-presenting surfaces. The unpatterned antigen-presenting synthetic surface may further include additional growth stimulatory, adhesive, and/or surface-blocking molecular ligands, as described above for antigen-presenting surfaces, each of which (if present) can be evenly distributed on the upatterned surface. For example, the unpatterned surface can include an adjunct stimulatory molecule such as IL-21 connected to the surface. The primary activating molecular ligands, co-activating molecular ligands, and/or additional ligands may be linked to the surface as described above for the antigen-presenting surfaces. As used herein, a surface having a ligand “distributed evenly” thereon is characterized in that no portion of the surface having a size of 10% the total surface area, or greater, has a statistically significant higher concentration of ligand as compared to the average ligand concentration of the total surface area of the surface. 
     Patterned Surface. 
     In various embodiments, the antigen-presenting synthetic surface may be patterned and may have a plurality of regions, each region including a plurality of the primary activating molecular ligands comprising MHC molecules, where the plurality of regions is separated by a region configured to substantially exclude the primary activating molecular ligands. The antigen-presenting synthetic surface may be a planar surface. In some embodiments, each of the plurality of regions including the at least a plurality of the primary activating molecular ligands may further include a plurality of the co-activating molecular ligands, e.g., a TCR co-activating molecule and/or an adjunct TCR activating molecule. The co-activating molecular ligands may be any of the co-activating molecular ligands as described above and in any combination. The primary activating molecular ligands and/or co-activating molecular ligands may be linked to the surface as described above for the antigen-presenting surfaces. The density of the primary activating molecular ligands and/or the co-activating molecular ligands in each of the regions containing the primary activating molecular ligands and/or the co-activating molecular ligands may be in the same range as the densities described above for antigen-presenting surfaces. In some embodiments, each of the plurality of regions comprising at least the plurality of the primary activating molecular ligands has an area of about 0.10 square microns to about 4.0 square microns. In other embodiments, the area of each of the plurality of regions may be about 0.20 square microns to about 0.8 square microns. The plurality of regions may be separated from each other by about 2 microns, about 3 microns, about 4 microns, or about 5 microns. The pitch between each region of the plurality and its neighbor may be about 2 microns, about 3 microns, about 4 microns, about 5 microns, or about 6 microns. See  FIGS. 7A and 7B  showing two embodiments of a patterned surface. 
     In various embodiments, the region configured to substantially exclude the primary activating molecular ligands comprising MHC molecules may also be configured to substantially exclude TCR co-activating molecules and/or adjunct TCR activating molecules. 
     In some embodiments, the region configured to substantially exclude the primary activating molecular ligands and optionally the TCR co-activating molecules and/or adjunct TCR activating molecules may also be configured to include one or more of surface-blocking molecular ligands, growth stimulatory molecules, additional stimulatory molecules, and adhesion stimulatory molecular ligands. In some embodiments, the growth stimulatory molecules and/or additional stimulatory molecules include a cytokine or fragment thereof, and may further include IL-21 or fragment thereof. In some embodiments, the region configured to substantially exclude the primary activating molecular ligands and optionally the TCR co-activating molecules and/or adjunct TCR activating molecules may further be configured to include one or more supportive moieties. The supportive moieties may provide adhesive motifs to support T lymphocyte growth or may provide hydrophilic moieties providing a generally supportive environment for cell growth. The moiety providing adhesive support may include a peptide sequence including a RGD motif. In other embodiments, the moiety providing adhesive support may be an ICAM sequence. A moiety providing hydrophilicity may be a moiety such as a PEG moiety or carboxylic acid substituted PEG moiety. 
     Microfluidic Device. 
     In some embodiments, a microfluidic device comprises a patterned antigen-presenting synthetic surface having a plurality of regions according to any of the foregoing embodiments. While the antigen-presenting surface of microfluidic device may be any microfluidic (or nanofluidic) device as described herein, the disclosure is not so limited. Other classes of microfluidic devices, including but not limited to microfluidic devices including microwells or microchambers such as described in WO2014/153651, WO2016/115337, or WO2017/124101, may be modified to either incorporate an antigen presenting surface as described in this section, or may be used in combination with the antigen-presenting beads or antigen-presenting wafers as described herein in the methods described in this disclosure. 
     In some embodiments, the antigen-presenting synthetic surface is an inner surface of a microfluidic device comprising one or more sequestration pens and a channel. At least part of a surface within one or more such sequestration pens may comprise a plurality of primary activating molecular ligands and a plurality of co-activating molecular ligands, e.g., comprising TCR co-activating molecules and/or adjunct TCR activating molecules. The primary activating molecular ligands and the co-activating molecular ligands may be any described above for antigen-presenting surfaces, and may be present in any concentration or combination as described above. The nature of the ligands attachment to the surface of the microfluidic device may be any described above as for antigen-presenting surfaces. In some embodiments, this surface within the one or more such sequestration pens can further comprise one or more of surface-blocking molecular ligands, growth stimulatory molecular ligands, additional stimulatory molecular ligands, and adhesion stimulatory molecular ligands. At least part of a surface of the channel may comprise surface-blocking molecular ligands, e.g., any of the regions configured to substantially exclude the primary activating molecular ligands described herein. In some embodiments, the surface of the channel comprises surface-blocking molecular ligands and optionally other non-stimulatory ligands, but is substantially free of other ligands present on the surface of the sequestration pen, e.g., primary activating molecular ligands and co-activating molecular ligands. 
     Modulation of Cell-to-Surface Adhesion. 
     In some embodiments, it can be useful to modulate the capacity for cells to adhere to surfaces within the microfluidic device. A surface that has substantially hydrophilic character may not provide anchoring points for cells requiring mechanical stress of adherence to grow and expand appropriately. A surface that presents an excess of such anchoring moieties may prevent successfully growing adherent cells from being exported from within a sequestration pen and out of the microfluidic device. In some embodiments, a covalently bound surface modification comprises surface contact moieties to help anchor adherent cells. The structures of the surfaces described herein and the methods of preparing them provide the ability to select the amount of anchoring moieties that may be desirable for a particular use. A very small percentage of adherent type motifs may be needed to provide a sufficiently adhesion enhancing environment. In some embodiments, the adhesion enhancing moieties are prepared before cells are introduced to the microfluidic device. Alternatively, an adhesion enhancing modified surface may be provided before introducing cells, and a further addition of another adhesion enhancing moiety may be made, which is designed to attach to the first modified surface either covalently or non-covalently (e.g., as in the base of biotin/streptavidin binding). 
     In some embodiments, adhesion enhancing surface modifications may modify the surface in a random pattern of individual molecules of a surface modifying ligand. In some other embodiments, a more concentrated pattern of adhesion enhancing surface modifications may be introduced by using polymers containing multiple adhesion enhancing motifs such as positively charged lysine side chains, which can create small regions of surface modification surrounded by the remainder of the surface, which may have hydrophilic surface modifications to modulate the adhesion enhancement. This may be further elaborated by use of dendritic polymers, having multiple adhesion enhancing ligands. A dendritic polymer type surface modifying compound or reagent may be present in a very small proportion relative to a second surface modification having only hydrophilic surface contact moieties, while still providing adhesion enhancement. Further a dendritic polymer type surface modifying compound or reagent may itself have a mixed set of end functionalities which can additionally modulate the behavior of the overall surface. 
     In some embodiments, it may be desirable to provide regioselective introduction of surfaces. For example, in the context of a microfluidic device comprising a microfluidic channel and sequestration pens, it may be desirable to provide a first type of surface within the microfluidic channel while providing a surface within the sequestration pens opening off of the channel that provides the ability to both culture adherent-type cells successfully as well as easily export them (e.g., using dielectrophoretic or other forces) when desired. In some embodiments, the adhesion enhancing modifications may include cleavable moieties. The cleavable moieties may be cleavable under conditions compatible with the cells being cultured within, such that at any desired timepoint, the cleavable moiety may be cleaved and the nature of the surface may alter to be less enhancing for adhesion. The underlying cleaved surface may be usefully non-fouling such that export is enhanced at that time. While the examples discussed herein focus on modulating adhesion and motility, the use of these regioselectively modified surfaces are not so limited. Different surface modifications for any kind of benefit for cells being cultured therein may be incorporated into the surface having a first and a second surface modification according to the disclosure. 
     Exemplary adherent motifs that may be used include poly-L-lysine, amine and the like, and the tripeptide sequence RGD, which is available as a biotinylated reagent and is easily adaptable to the methods described herein. Other larger biomolecules that may be used include fibronectin, laminin or collagen, amongst others. A surface modification having a structure of Formula XXVI as defined in WO2017/205830, including a polyglutamic acid surface contact moiety, can induce adherent cells to attach and grow viably. Another motif that may assist in providing an adherent site is an Elastin Like Peptide (ELP), which includes a repeat sequence of VPGXG, where X is a variable amino acid which can modulate the effects of the motif. 
     In some embodiments, in the context of a microfluidic device comprising a microfluidic channel and sequestration pens, a surface of the flow region (e.g., microfluidic channel) may be modified with a first covalently bound surface modification and a surface of the at least one sequestration pen may be modified with a second covalently bound surface modification, wherein the first and the second covalently bound surface modification have different surface contact moieties, different reactive moieties, or a combination thereof. The first and the second covalently bound surface modifications may be selected from any of Formula XXX, Formula V, Formula VII, Formula XXXI, Formula VIII, and/or Formula IX, all of which are as defined in WO2017/205830. When the first and the second covalently bound surface modifications both include functionalized surface of Formula XXX, Formula V, or Formula VII as defined in WO2017/205830, then orthogonal reaction chemistries are selected for the choice of the first reactive moiety and the second reactive moiety. In various embodiments, all the surfaces of the flow region may be modified with the first covalent surface modification and all the surfaces of the at least one sequestration pen may be modified with the second covalent modification. 
     Methods of Preparing an Antigen-Presenting Synthetic Surface; Covalently Functionalized Surface 
       FIGS. 5A and 5B  show the structure of an antigen-presenting synthetic surface as it is constructed from an unmodified surface, adding the activating, co-activating and surface-blocking molecular ligands in one or more steps.  FIG. 5A  shows the process and structure for an antigen-presenting synthetic surface having a single region, while  FIG. 5B  shows the process and structure of each intermediate and final product for an antigen-presenting synthetic surface having two regions. 
     Turning to  FIG. 5A , the schematic representation illustrates an exemplary procedure for preparing an antigen-presenting surface starting with a synthetic reactive surface comprising a plurality of surface-exposed moieties (SEM). Reactive moieties RM and surface-blocking molecular ligands SB, if added at this point in the preparation, are introduced by reacting the SEMs with appropriate preparing reagent(s), providing an intermediate reactive surface. The reactive moieties RM introduced to the intermediate reactive surface may be any reactive moiety described herein and may be linked to the intermediate reactive surface by any linker described herein. The intermediate reactive surface includes at least reactive moieties RM, and, in some embodiments, may include surface-blocking molecular ligands SB, which may be any surface-blocking molecular ligand as described herein. 
     The intermediate reactive surface is then treated with functionalizing reagents including binding moieties BM, where the functionalizing reagents react with the reactive moieties RM to introduce binding moiety BM ligands. The binding moieties so introduced may be any binding moiety BM described herein. The binding moiety BM may be streptaviding or biotin. In some embodiments, the binding moiety BM is streptavidin which is covalently attached via a linker to the covalently functionalized surface, through a reaction with a reactive moiety RM. In some other embodiments, the covalently functionalized surface may introduce a streptavidin binding moiety non-covalently, in a two part structure. This two part structure is introduced by contacting the intermediate reactive surface with a first functionalizing reagent to introduce a biotin moiety covalently attached via a linker through reaction with the reactive moieties RM. Subsequent introduction of streptavidin, as a second functionalizing reagent, provides the covalently functionalized surface wherein the binding moiety BM, streptavidin, is non-covalently attached to a biotin moiety which itself is covalently attached to the surface. Surface-blocking molecular ligands SB′ may be introduced at the same time as the introduction of the binding moieties or may be introduced to the covalently functionalized surface subsequent to the introduction of the binding moieties. The surface-blocking molecular ligands SB′ may be any surface-blocking molecular ligand as described herein and may be the same as or different from surface-blocking molecular ligands SB, if surface-blocking molecular ligands SB are present. In some embodiments, surface-blocking molecular ligands SB may be present and there may be no surface-blocking molecular ligands SB′. Alternatively, there may be surface-blocking molecular ligands SB′ but no surface-blocking molecular ligands SB. In some embodiments, both surface-blocking molecular ligands SB and SB′ are present. Without being bound by theory, there may be some reactive moieties RM left unreacted upon the covalently functionalized surface but there are insufficient numbers of reactive moieties RM present to prevent the product antigen presenting synthetic surface from functioning. Primary activating ligands MHC and Co-Activating Ligands Co-A 1  and Co-A 2  are introduced by reacting the binding moieties BM, of the covalently functionalized surface, with appropriate activating ligand reagents, providing the antigen-presenting synthetic surface. Co-A 1  and Co-A 2  may be the same or different co-activating ligands. For example, Co-A 1  and Co-A 2  can comprise one, the other, or collectively both of a TCR co-activating molecule and a TCR adjunct activating molecule. Co-A 1  and/or Co-A 2 , may be any combination of TCR co-activating molecule and a TCR adjunct activating molecule as described herein. In some embodiments, the primary activating ligand MHC may be introduced to the covalently functionalized surface, before the covalently functionalized surface is contacted with the co-activating ligands Co-A 1  and/or Co-A 2 . In other embodiments, the primary activating ligand MHC may be introduced to the covalently functionalized surface concurrently with or subsequently to the introduction of the Co-Activating ligands Co-A 1  and Co-A 2 . In some embodiments, not shown in  FIG. 5A , after introduction of the primary activating ligand MHC and co-activating ligands Co-A 1  and/or Co-A 2 , surface-blocking molecular ligands SB may be introduced to the antigen presenting synthetic surface by reacting surface-blocking molecules with remaining reactive moieties RM still present on the antigen-presenting synthetic surface. Also included but not illustrated in  FIG. 5A , is the introduction of Secondary Ligands SL, which may be one or more growth stimulatory molecular ligands and/or adhesion stimulatory molecular ligands. Secondary Ligands SL may be any of these classes of ligands. 
       FIG. 5B  provides a schematic illustration of an exemplary procedure for preparing an antigen-presenting surface comprising first and second regions starting with a synthetic reactive surface comprising a plurality of surface-exposed moieties (SEM). The surface exposed moieties SEM in Region  1  may be different from the surface exposed moieties SEM 2  in Region  2 , as shown in  FIG. 6 , where different materials may be present at the surface of the synthetic reactive surface. Reactive moieties RM are introduced in region  1  and substantially not in region  2 , while reactive moieties RM 2  are introduced in region  2 , and substantially not in region  1 , due to the use of orthogonal chemistries for each of SEM and SEM 2 . For example, as shown in  FIG. 6 , the SEM of region  1  may be reacted with an alkoxysiloxane reagent comprising an azide RM, while the SEM 2  of region  2  may be reacted with a phosphonic acid reagent comprising an alkynyl RM. Surface-blocking molecular ligands SB 1  are introduced in region  1 , and substantially not in region  2 , by reacting the SEMs with appropriate preparing reagent(s (e.g, for a surface like region  1  of  FIG. 6 , the reagent would be an alkoxysiloxane reagnt including a surface-blocking group SB). An intermediate reactive surface having differentiated reactive moieties result from this process. Based on the differentiated reactive moieties RM and RM 2 , further orthogonal chemistries can introduce binding moieties BM and surface-blocking molecular ligands SB 1 ′ in region  1  and not substantially in region  2 , and surface-blocking molecular ligands SB 2  are introduced in region  2 , and not substantially in region  1 . Thus, a covalently functionalized surface having two different regions is provided. The SB 1 ′ may be the same as or different from SB 1 ; SB 1 ′ may be the same as or different from SB 2 ; and SB 2  may be the same as or different from SB 1 . Primary activating ligands MHC and Co-Activating Ligands Co-A 1  and Co-A 2  are introduced in region  1  by reacting binding moieties BM with appropriate activating ligand reagents, and secondary ligands SL are formed in region  2  by reacting RMs with appropriate reagent(s), providing the antigen-presenting synthetic surface. Secondary Ligands SL may be any of the classes of molecular ligands as described for  FIG. 5A . The primary activating ligand MHC may be introduced before introducing the Co-Activating Ligands, similarly to the process described for  FIG. 5A . Co-A 1  and Co-A 2  may be the same or different co-activating ligands. For example, Co-A 1  and Co-A 2  can comprise one, the other, or collectively both of a TCR co-activating molecule and a TCR adjunct activating molecule. Each of SEM, RM, SB, primary activating ligand MHC, Co-Activating Ligands Co-A 1  and Co-A 2 , and secondary ligands SL may be any SEM, RM, SB, primary activating ligand MHC, Co-Activating Ligands Co-A 1  and Co-A 2 , and secondary ligands SL described herein. 
     Methods of Preparing an Antigen-Presenting Synthetic Surface 
     A method of preparing an antigen-presenting synthetic surface for activating a T lymphocyte (T cell), is provided, comprising: reacting a plurality of primary activating molecules, with a first plurality of binding moieties of a covalently functionalized synthetic surface comprising binding moieties (e.g., a biotin-binding agent such as streptavidin, or biotin moieties that are noncovalently associated with a biotin-binding agent such as streptavidin), wherein each of the first plurality of binding moieties is configured for binding the primary activating molecule; and reacting a plurality of co-activating molecules, each comprising: a T cell receptor (TCR) co-activating molecule; or an adjunct TCR activating molecule, with a second plurality of binding moieties of the covalently functionalized synthetic surface, wherein each of the second plurality of binding moieties is configured for binding the co-activating molecule, thereby providing a plurality of specifically bound primary activating molecular ligands and a plurality of specifically bound co-activating molecular ligands on the antigen-presenting synthetic surface. 
     Also provided is a covalently functionalized synthetic surface comprising binding moieties (e.g., a biotin-binding agent such as streptavidin, or biotin moieties that are noncovalently associated with a biotin-binding agent such as streptavidin) and at least a first plurality of surface-blocking molecular ligands. To the extent that the following discussion describes features of a covalently functionalized synthetic surface, it applies both to embodiments of the covalently functionalized synthetic surface and to embodiments of methods of preparing an antigen-presenting surface in which a covalently functionalized synthetic surface is used. 
     The covalently functionalized synthetic surface may be any of the surface types described herein, e.g., a bead, wafer, inner surface of a microfluidic device, or tube (e.g., glass or polymer tube). The surface material may comprise, e.g., metal, glass, ceramic, polymer, or a metal oxide. The microfluidic device may be any microfluidic device as described herein, and may have any combination of features. The bead can be a bead with a surface-area that is within 10% of the surface-area of a sphere of an equal volume or diameter, as discussed herein in the section regarding antigen-presenting synthetic surfaces. In some embodiments, the bead may be a bead having a surface area that exceeds 10% of the surface area of a sphere of an equal volume or diameter, as discussed herein for antigen presenting surfaces. In some embodiments, the bead is not a bead that has a surface area that exceeds 10% of the surface area of a sphere of an equal volume or diameter, as discussed herein for antigen presenting surfaces. 
     The primary activating molecules and co-activating molecules may each be any such molecule described herein, and any combination thereof may be used. Thus, a primary activating molecule can comprise an MHC molecule and, optionally, an antigenic peptide; and a co-activating molecule can comprise any of the TCR co-activating molecules described herein or any of the adjunt TCR activating molecules described herein. 
     In some embodiments, reacting a plurality of primary activating molecules with a first plurality of binding moieties of a covalently functionalized synthetic surface comprising binding moieties comprises forming a noncovalent association between the primary activating molecules and the binding moieties. For example, the primary activating molecules can comprise biotin and the binding moieties can comprise a biotin-binding agent such as streptavidin (e.g., which may be covalently bound to the surface or which may be non-covalently bound to a second biotin which itself is covalently bound to the surface). In some embodiments, the biotin-binding agent such as streptavidin is linked to the surface through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetwteen. For example, the biotin-binding agent may be linked to the surface through a series of one or more linkers having a selected length as described. In another example, both the binding moieties and the primary activating molecules can comprise biotin and a free, multivalent biotin-binding agent, such as streptavidin, can be used as a noncovalent linking agent. Any other suitable noncovalent binding pair, such as those described elsewhere herein, can also be used. 
     Alternatively, reacting a plurality of primary activating molecules with a first plurality of binding moieties of a covalently functionalized synthetic surface comprising binding moieties can comprise forming a covalent bond. For example, an azide-alkyne reaction (such as any of those described elsewhere herein) can be used to form the covalent bond, where the primary activating molecules and the binding moieties comprise, respectively, an azide and an alkyne, or an alkyne and an azide. Other reaction pairs may be used, as is known in the art, including but not limited to maleimide and sulfides. More generally, exemplary functionalities useful for forming covalent bonds include azide, carboxylic acid and active esters thereof, succiniimide ester, maleimide, keto, sulfonyl halides, sulfonic acid, dibenzocyclooctyne, alkene, alkyne, and the like. Skilled artisans are familiar with appropriate combinations and reaction conditions for forming covalent bonds using such moieties. 
     Where the covalently functionalized synthetic surface comprises a covalently associated biotin, the surface can further comprise noncovalently associated biotin-binding agent (e.g., streptavidin), such that the surface can be reacted with primary activating molecules and co-activating molecules that comprise biotin moieties. In some embodiments, the method of preparing an antigen-presenting synthetic surface comprises reacting a covalently functionalized synthetic surface comprising a covalently associated biotin with a biotin-binding agent (e.g., streptavidin), and then with primary activating molecules and co-activating molecules comprising biotin moieties. In some embodiments, the biotin of the covalently functionalized surface is linked to the surface through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetween. 
     In some embodiments, the reaction provides any of the densities described herein of primary activating molecular ligands on the surface, such as about 4×10 2  to about 3×10 4 , 4×10 2  to about 2×10 3 , about 5×10 3  to about 3×10 4 , about 5×10 3  to about 2×10 4 , or about 1×10 4  to about 2×10 4  molecules per square micron. 
     In some embodiments, reacting a plurality of co-activating molecules, each comprising: a T cell receptor (TCR) co-activating molecule; or an adjunct TCR activating molecule, with a second plurality of binding moieties of the covalently functionalized synthetic surface comprises forming a noncovalent association between the co-activating molecules and the binding moieties. Any of the embodiments described above or set forth in any embodiments disclosed herein with respect to primary activating molecules involving noncovalent binding pairs such as biotin and a biotin-binding agent such as streptavidin may be used. 
     Alternatively, reacting a plurality of co-activating molecules with a second plurality of binding moieties of the covalently functionalized synthetic surface can comprise forming a covalent bond. For example, an azide-alkyne reaction (such as any of those described elsewhere herein) can be used to form the covalent bond, where the primary activating molecules and the binding moieties comprise, respectively, an azide and an alkyne, or an alkyne and an azide. 
     In some embodiments, the reaction provides any of the densities described herein of co-activating molecular ligands on the surface, such as from about 4×10 2  to about 3×10 4 , 4×10 2  to about 2×10 3 , about 5×10 3  to about 3×10 4 , about 5×10 3  to about 2×10 4 , or about 1×10 4  to about 2×10 4  molecules per square micron. 
     In some embodiments, the reaction provides TCR co-activating molecules and adjunct TCR activating molecules on the surface in any of the ratios described herein, such as 100:1 to 1:100, 10:1 to 1:20, 5:1 to 1:5, or 3:1 to 1:3, wherein each of the foregoing values can be modified by “about.” 
     In some embodiments, the reactions described above or set forth in any embodiments disclosed herein provide primary activating molecular ligands and co-activating molecular ligands on the surface in any of the ratios described herein, such as about 1:1 to about 2:1; about 1:1; or about 3:1 to about 1:3. 
     In some embodiments, a method of preparing an antigen-presenting surface further comprises reacting a plurality of surface-blocking molecules with a third plurality of binding moieties of the covalently functionalized surface, wherein each of the binding moieties of the third plurality is configured for binding the surface-blocking molecule. Any surface-blocking molecule described elsewhere herein may be used. Any of the reaction approaches described herein for forming noncovalent associations or a covalent bond may be used. 
     In some embodiments, a method of preparing an antigen-presenting surface further comprises reacting a plurality of adhesion stimulatory molecular ligands, wherein each adhesion stimulatory molecular ligand includes a ligand for a cell adhesion receptor including an ICAM protein sequence, with a fourth plurality of binding moieties of the covalently functionalized bead, wherein each of the binding moieties of the fourth plurality is configured for binding with the cell adhesion receptor ligand molecule. Any of the reaction approaches described herein for forming noncovalent associations or a covalent bond may be used. 
     In some embodiments, a method of preparing an antigen-presenting surface further comprises producing the intermediate reactive surface. This can include, e.g., reacting at least a first portion of surface-exposed moieties disposed at a surface of a synthetic reactive surface with a plurality of intermediate preparation molecules including reactive moieties, thereby producing the intermediate reactive surface. Methods of preparing a covalently functionalized surface, which can be used as the intermediate reactive surface, are described in detail elsewhere herein. Producing the intermediate reactive surface can comprise any of the features described herein with respect to methods of preparing a covalently functionalized surface. 
     In some embodiments, the methods further comprise modulating the capacity for cells to adhere to surfaces within the microfluidic device, e.g., by providing anchoring points for cells requiring mechanical stress of adherence to grow and expand appropriately. This can be accomplished by introducing a covalently bound surface modification comprising surface contact moieties to help anchor adherent cells. Any of the surface contact moieties described elsewhere herein can be used. 
     The covalently functionalized synthetic surface can comprise moieties suitable for use in any of the reactions described herein. 
     Methods of Preparing a Covalently Functionalized Surface 
     Also provided is a method of preparing a covalently functionalized surface including a plurality of streptavidin or biotin functionalities and at least a first plurality of surface-blocking molecular ligands, wherein the method includes: reacting at least a first subset of reactive moieties of an intermediate reactive synthetic surface with a plurality of linking reagents, each linking reagent including streptavidin or biotin; and reacting at least a second subset of reactive moieties of the intermediate reactive synthetic surface with a plurality of surface-blocking molecules, thereby providing the covalently functionalized synthetic surface including at the least one plurality of streptavidin or biotin functionalities and at the least first plurality of surface-blocking molecular ligands. Generally only one or the other of a linking reagent including streptavidin or a linking reagent including biotin is used. The intermediate reactive synthetic surface may be any of the surface types described herein, e.g., a bead, wafer, inner surface of a microfluidic device, or tube (e.g., glass or polymer tube). The surface material may comprise, e.g., metal, glass, ceramic, polymer, or a metal oxide. The antigen-presenting microfluidic device may be any microfluidic device as described herein, and may have any combination of features. The bead can be a bead with a surface-area is within 10% of the surface-area of a sphere of an equal volume or diameter, as discussed herein in the section regarding antigen-presenting synthetic surfaces. 
     In embodiments in which the linking reagents include biotin, the method can further comprise noncovalently associating streptavidin with the biotin. In such embodiments, with reference to  FIG. 5A , the conversion of a reactive moiety RM to a binding moiety BM can comprise covalently attaching a biotin (corresponding to the additional biotin in the above description) through reaction with the RM and then associating a streptavidin noncovalently with the covalently attached biotin. 
     In some embodiments, the reactive moieties of an intermediate reactive synthetic surface are linked to the surface through a series of 5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or, in some embodiments, greater numbers of bonds. For example, the reactive moieties can be linked through a series of 15 bonds, e.g., using (11-(X)undecyl)trimethoxy silane, where X is the reactive moiety (e.g., X can be azido). With respect to linking reagents including biotin, biotin can then be covalently associated using a linking reagent such as one having the general structure DBCO-PEG 4 -biotin (commercially available from BroadPharm). In some embodiments, the biotin is linked to the surface through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetwteen. With respect to linking reagents including streptavidin, streptavidin can then be covalently associated using a linking reagent such as one having the general structure DBCO-PEG 13 -succinimide, followed by reaction of streptavidin with the succinimide. In some embodiments, the streptavidin is linked to the surface through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetwteen. The number of bonds through which a moiety is linked to a surface can be varied, e.g., by using reagents similar to those mentioned above but with alkylene and/or PEG chains of different lengths. 
     In some embodiments, the reactive moieties of at least first region of the intermediate reactive synthetic surface include azide moieties. In some embodiments, covalent bonds are formed through an azide-alkyne reaction, such as any azide-alkyne reaction described elsewhere herein. 
     In some embodiments, the covalently functionalized synthetic surface includes a second region wherein the plurality of streptavidin functionalities is excluded. In some embodiments, the at least first plurality of surface-blocking molecular ligands are disposed in the second region of the covalently functionalized synthetic surface. 
     In some embodiments, a method further includes reacting a second plurality of surface-blocking molecules with a second subset of reactive moieties in the at least first region of the intermediate reactive synthetic surface. 
     In some embodiments, the reacting of the plurality of streptavidin functionalities and the reacting of the at least first plurality of surface-blocking molecules is performed at a plurality of sub-regions of the at least first region of the covalently prepared synthetic surface including reactive moieties. 
     In some embodiments, the second portion of the reactive synthetic surface includes surface exposed moieties configured to substantially not react with the pluralities of the primary activating and co-activating molecules. 
     In some embodiments, a method further includes preparing the intermediate reactive synthetic surface, including: reacting at least a first surface preparing reagent including azide reactive moieties with surface-exposed moieties disposed at at least a first region of a reactive synthetic surface. 
     In some embodiments, the surface-exposed moieties are nucleophilic moieties. In some embodiments, the nucleophilic moiety of the surface is a hydroxide, amino or thiol. In some other embodiments, the nucleophilic moiety of the surface may be a hydroxide. 
     In some embodiments, the surface-exposed moieties are displaceable moieties. 
     In some embodiments, where two modifying reagents are used, the reaction of the first modifying reagent and the reaction of the second modifying reagent with the surface may occur at random locations upon the surface. In other embodiments, the reaction of the first modifying reagent may occurs within a first region of the surface and reaction of the second modifying reagent may occur within a second region of the surface abutting the first region. For example, the surfaces within the channel of a microfluidic device may be selectively modified with a first surface modification and the surfaces within the sequestration pen, which abut the surfaces within the channel, may be selectively modified with a second, different surface modification. 
     In yet other embodiments, the reaction of the first modifying reagent may occurs within a plurality of first regions separated from each other on the at least one surface, and the reaction of the second modifying reaction may occur at a second region surrounding the plurality of first regions separated from each other. 
     In various embodiments, modification of one or more surfaces of a microfluidic device to introduce a combination of a first surface modification and a second surface modification may be performed after the microfluidic device has been assembled. For one nonlimiting example, the first and second surface modification may be introduced by chemical vapor deposition after assembly of the microfluidic device. In another nonlimiting example, a functionalized surface having a first surface modification having a first reactive moiety and a second surface modification having a second, orthogonal reactive moiety may be introduced. Differential conversion to two different surface modifying ligands having two different surface contact moieties can follow. 
     In some embodiments, at least one of the combination of first and second surface modification may be performed before assembly of the microfluidic device. In some embodiments, modifying the at least one surface may be performed after assembly of the microfluidic device. 
     In some embodiments, a covalently functionalized surface is prepared comprising a binding agent. In some embodiments, the distribution of the plurality of binding agent (e.g., plurality of multivalent binding agent, such as a tetravalent binding agent, e.g., streptavidin functionalities, which may be covalently associated or noncovalently associated with a covalently bound biotin) on the covalently functionalized synthetic surface is from about 6×10 2  to about 5×10 3  molecules per square micron, in each region where it is attached. In some embodiments, the distribution of the plurality of binding agent (e.g., plurality of multivalent binding agent, such as a trivalent binding agent) is about about 1.5×10 3  to about 1×10 4 , about 1.5×10 3  to about 7.5×10 3 , or about 3×10 3  to about 7.5×10 3  molecules per square micron, in each region where it is attached. In some embodiments, the distribution of the plurality of binding agent (e.g., plurality of multivalent binding agent, such as a divalent binding agent) is about 2.5×10 3  to about 1.5×10 4 , about 2.5×10 3  to about 1×10 4 , or about 5×10 3  to about 1×10 4  molecules per square micron, in each region where it is attached. In some embodiments, the distribution of the plurality of binding agent (e.g., plurality of monovalent binding agent) is about 5×10 3  to about 3×10 4 , about 5×10 3  to about 2×10 4 , or about 1×10 4  to about 2×10 4  molecules per square micron, in each region where it is attached. 
     In some embodiments, a covalently functionalized surface is prepared comprising a binding agent, in which the distribution of the plurality of binding agent (e.g., streptavidin functionalities, which may be covalently associated or noncovalently associated with a covalently bound biotin) on the covalently functionalized synthetic surface is from about 1×10 4  to about 1×10 6  molecules per square micron, in each region where it is attached. 
     In some embodiments, a combined method comprising preparing a covalently functionalized surface and then preparing an antigen-presenting synthetic surface is provided. As such, any suitable combination of steps for preparing the covalently functionalized surface and steps for preparing the antigen-presenting synthetic surface may be used. 
     Additional Aspects of Surface Preparation and Covalently Functionalized Surfaces. 
     Any method of preparing a surface described herein, including methods of preparing an antigen-presenting synthetic surface and methods of preparing a covalently functionalized surface, may further comprise one or more of the following aspects. A covalently functionalized surface may further comprise one or more of the following aspects applicable to such surfaces, such as reactive groups. 
     Azide-Alkyne Reactions. 
     In some embodiments, covalent bonds are formed by reacting an alkyne, such as an acyclic alkyne, with an azide. For example, a “Click” cyclization reaction may be performed, which is catalyzed by a copper (I) salt. When a copper (I) salt is used to catalyze the reaction, the reaction mixture may optionally include other reagents which can enhance the rate or extent of reaction. When an alkyne, e.g., of a surface modifying reagent or a functionalized surface is a cyclooctyne, the “Click” cyclization reaction with an azide of the corresponding functionalized surface or the surface modifying reagent may be copper-free. A “Click” cyclization reaction can thereby be used to couple a surface modifying ligand to a functionalized surface to form a covalently modified surface. 
     Copper Catalysts. 
     Any suitable copper (I) catalyst may be used. In some embodiments, copper (I) iodide, copper (I) chloride, copper (I) bromide or another copper (I) salt. In other embodiments, a copper (II) salt may be used in combination with a reducing agent such as ascorbate to generate a copper (I) species in situ. Copper sulfate or copper acetate are non-limiting examples of a suitable copper (II) salt. In other embodiments, a reducing agent such as ascorbate may be present in combination with a copper (I) salt to ensure sufficient copper (I) species during the course of the reaction. Copper metal may be used to provide Cu(I) species in a redox reaction also producing Cu(II) species. Coordination complexes of copper such as [CuBr(PPh 3 ) 3 ], silicotungstate complexes of copper, [Cu(CH 3 CN) 4 ]PF 6 , or (Eto) 3 P CuI may be used. In yet other embodiments, silica supported copper catalyst, copper nanoclusters or copper/cuprous oxide nanoparticles may be employed as the catalyst. 
     Other Reaction Enhancers. 
     As described above, reducing agents such as sodium ascorbate may be used to permit copper (I) species to be maintained throughout the reaction, even if oxygen is not rigorously excluded from the reaction. Other auxiliary ligands may be included in the reaction mixture, to stabilize the copper (I) species. Triazolyl containing ligands can be used, including but not limited to tris(benzyl-1H-1,2,3-triazol-4-yl) methylamine (TBTA) or 3 [tris(3-hydroxypropyltriazolylmethyl)amine (THPTA). Another class of auxiliary ligand that can be used to facilitate reaction is a sulfonated bathophenanthroline, which is water soluble, as well, and can be used when oxygen can be excluded. Other chemical couplings as are known in the art may be used to couple a surface modifying reagent to a functionalized surface. 
     Cleaning the Surface. 
     The surface to be modified may be cleaned before modification to ensure that the nucleophilic moieties on the surface are freely available for reaction, e.g., not covered by oils or adhesives. Cleaning may be accomplished by any suitable method including treatment with solvents including alcohols or acetone, sonication, steam cleaning and the like. Alternatively, or in addition, such pre-cleaning can include cleaning (e.g., of the cover, the microfluidic circuit material, and/or the substrate in the context of components of a microfluidic device) in an oxygen plasma cleaner, which can remove various impurities, while at the same time introducing an oxidized surface (e.g. oxides at the surface, which may be covalently modified as described herein). Alternatively, liquid-phase treatments, such as a mixture of hydrochloric acid and hydrogen peroxide or a mixture of sulfuric acid and hydrogen peroxide (e.g., piranha solution, which may have a ratio of sulfuric acid to hydrogen peroxide from about 3:1 to about 7:1) may be used in place of an oxygen plasma cleaner. This can advantageously provide more sites for modification on the surface, thereby providing a more closely packed modified surface layer. 
     Components of Microfluidic Devices. 
     A surface of a material that may be used as a component of a microfluidic device may be modified before assembly thereof. Alternatively, a partially or completely constructed microfluidic device may be modified such that all surfaces that will contact biomaterials including biomolecules and/or micro-objects (which may include biological micro-objects) are modified at the same time. In some embodiments, the entire interior of a device and/or apparatus may be modified, even if there are differing materials at different surfaces within the device and/or apparatus. This discussion also applies to the methods of preparing an antigen-presenting synthetic surface described herein. 
     When an interior surface of a microfluidic device reacted with a surface modifying reagent, the reaction may be performed by flowing a solution of the surface modifying reagent into and through the microfluidic device. 
     Surface Modifying Reagent Solutions and Reaction Conditions. 
     In various embodiments, the surface modifying reagent may be used in a liquid phase surface modification reaction, e.g., wherein the surface modifying reagent is provided in solution, such as an aqueous solution. Other useful solvents include aqueous dimethyl sulfoxide (DMSO), DMF, acetonitrile, or an alcohol may be used. For example, surfaces activated with tosyl groups or labeled with epoxy groups can be modified in liquid phase reactions. Reactions to couple biotin or proteins such as antibodies, MHCs, or streptavidin to a binding moiety can also be performed as liquid phase reactions. 
     The reaction may be performed at room temperature or at elevated temperatures. In some embodiments, the reaction is performed at a temperature in a range from about 15° C. to about 60° C.; about 15° C. to about 55° C.; about 15° C. to about 50° C.; about 20° C. to about 45° C. In some embodiments, the reaction to convert a functionalized surface of a microfluidic device to a covalently modified surface is performed at a temperature of about 15° C., 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., or about 60° C. 
     Alternatively, a surface modifying reagent may be used in a vapor phase surface modification reaction. For example, silica surfaces and other surfaces comprising hydroxyl groups can be modified in a vapor phase reaction. In some embodiments, a surface (e.g., a silicon surface) is treated with plasma (e.g., using an oxygen plasma cleaner; see the Examples for exemplary treatment conditions). In some embodiments, a surface, such as a plasma treated and/or silicon surface, is reacted under vacuum with a preparing reagent, e.g., comprising a methoxysilane and an azide, such as (11-azidoundecyl) trimethoxy silane. The preparing reagent can be provided initially in liquid form in a vessel separate from the surface and can be vaporized to render it available for reaction with the surface. A water source such as a hydrated salt, e.g., magnesium sulfate heptahydrate can also be provided, e.g., in a further separate vessel. For example, foil boat(s) in the bottom of a vacuum reactor can be used as the separate vessel(s). Exemplary reaction conditions and procedures include pumping the chamber to about 750 mTorr using a vacuum pump and then sealing the chamber. The vacuum reactor can then be incubated at a higher-than ambient temperature for an appropriate length of time, e.g., by placing it within an oven heated at 110° C. for 24-48 h. Following the reaction period, the chamber can be allowed to cool and an inert gas such as argon can be introduced to the evacuated chamber. The surface can be rinsed with one or more appropriate liquids such as acetone and/or isopropanol, and then dried under a stream of inert gas such as nitrogen. Confirmation of introduction of the modified surface can be obtained using techniques such as ellipsometry and contact angle goniometry. 
     Additional modified surfaces, surface-modifying reagents, and related methods that can be employed in accordance with this disclosure are described in WO2017/205830, published Nov. 30, 2017, which is incorporated herein by reference for all purposes. 
     Methods of Activating a T Lymphocyte. 
     A method of activating T lymphocytes is provided, comprising: contacting a plurality of T lymphocytes with a antigen-presenting synthetic surface including: a plurality of primary activating molecular ligands, each including a major histocompatibility (MHC) molecule configured to bind to a T cell receptor of the T cell; and a plurality of co-activating molecular ligands each including a T cell receptor (TCR) co-activating molecule or an adjunct TCR activating molecule; and, culturing the plurality of T lymphocytes in contact with the antigen-presenting synthetic surface, thereby converting at least a portion of the plurality of T Lymphocytes to activated T lymphocytes. The antigen-presenting surface may be any antigen-presenting surface as described herein. In some embodiments, the MHC molecule is an MHC Class 1 molecule. Any of the antigen-presenting synthetic surfaces described herein can be used. In various embodiments, the plurality of MHC molecules may each include an amino acid sequence, and further may be connected to the antigen-presenting synthetic surface via a C-terminal connection of the amino acid sequence. Alternatively, the MHC molecule can be connected to the antigen-presenting synthetic surface through a noncovalent association. Any noncovalent association can be used, e.g., biotinylation of the MHC and binding thereof to streptavidin on the surface. In various embodiments, the MHC molecule may further include an antigen molecule, such as a tumor associated antigen, e.g., any of the tumor associated antigens described herein. In some embodiments, the antigen molecule may be MART1, NYESO1, SLC45A2, TCL1, or VCX3A. 
     In some embodiments, the co-activating molecules may be connected to the antigen-presenting synthetic surface, as described herein. The T cell receptor (TCR) co-activating molecule or an adjunct TCR activating molecule of the plurality of co-activating molecules may be any TCR co-activating molecule or any adjunct TCR activating molecule as described herein and may be provided in any ratio described herein. 
     In various embodiments the method may further include contacting the plurality of T lymphocytes with a plurality of growth stimulatory molecular ligands. In some embodiments, each of the growth stimulatory molecular ligands may includes a growth factor receptor ligand. In some embodiments, contacting the plurality of T lymphocytes with the plurality of growth stimulatory molecular ligands may be performed after a first period of culturing of at least one day. In some embodiments, the plurality of growth stimulatory molecular ligands may include IL-21 or a fragment thereof. In various embodiments, the plurality of growth stimulatory molecular ligands may be connected to the antigen-presenting synthetic surface. In some embodiments, the plurality of growth stimulatory molecular ligands may be connected to a surface (e.g., of a bead) that is a different surface than the antigen-presenting synthetic surface including the biomolecules including MHC molecules. In some embodiments, the plurality of growth stimulatory molecular ligands may be connected to the antigen-presenting synthetic surface including MHC molecules. 
     In various embodiments, the method may include using antigen presenting surfaces on beads. When beads having antigen presenting surfaces are used, the ratio of beads to T lymphocytes may be about 1:1; about 3:1; about 5:1; about 7:1 or about 10:1. The beads may have antigen presenting MHC molecules and anti-CD28 antibodies attached thereto in any method as described herein. In some embodiments, IL-21 may also be attached to the antigen presenting surface of the bead. In other embodiments, IL-21 may be attached to a second bead that has IL-21 as the only biomolecule contributing to activation. 
     In other embodiments, the method may be performed using a planar surface which may be patterned or unpatterned. 
     In various embodiments, a first period of culturing may be performed for 4, 5, 6, 7, or 8 days. During the first period of culturing, growth stimulatory molecules such as IL-21, IL-2, and/or IL-7 may be added in solution or may be added on bead to feed the T lymphocytes. 
     At the end of a first period of culture, the population of cells may include a mixture of unactivated and activated T lymphocytes. Flow cytometry using multiple cell surface markers can be performed to determine the extent of activation and the phenotype of the cells analyzed. 
     A second period of culture can be performed. If the antigen presenting surfaces are beads, a second aliquot of beads containing the primary activating molecular ligand including the MHC molecule, which includes the tumor associated antigen and co-activating molecules (e.g., TCR co-activating molecules and/or adjunct TCR activating molecules, such as anti-CD28 antibodies and/or anti-CD2 antibodies, respectively) may be provided to the T lymphocytes, e.g., by addition to the wellplate, chamber of the fluidic circuit containing device, or microfluidic device having sequestration pens as described herein. The antigen presenting beads may further include additional growth stimulatory molecules, e.g., IL-21, connected thereto. The antigen presenting beads may be added to the cells being cultured in about a 1:1; about 3:1, about 5:1; or about 10:1 ratio to the cells. In some embodiments, a second aliquot of IL-21 may be added as a second set of beads having IL-21 connected thereto, or further, may be added as a solution. IL-2 and IL-7 may also be added during the second period of culturing to activate additional numbers of T lymphocytes. 
     When a patterned or unpatterned wafer, inner surface of a fluidic circuit containing device, inner surface of a tube, or inner surface of a microfluidic device having sequestration pens is used, a second period of culturing may be accomplished by continuing to culture in contact with same antigen presenting surface. Alternatively, a new antigen presenting surface may be brought into contact with the T lymphocytes resultant from the first period of culturing. In other embodiments, antigen presenting beads, like any described above or set forth in any embodiments disclosed herein, may be added to the wells or interior chamber of a fluidic circuit containing device or the sequestration pens of a microfluidic device. Growth stimulatory molecules such as IL-21, IL-2, IL-7, or a combination thereof may be added in solution or on beads. In some embodiments, IL-2 and IL-7 are added. 
     At the conclusion of the second culturing period, flow cytometry analysis can be performed to determine the extent of activation and to determine the phenotype of the further activated T lymphocytes present at that time. 
     In some embodiments, a third period of culturing may be included. The third period may have any of the features described herein with respect to the second period. In some embodiments, the third period is performed in the same way as the second period. For example, and all of the actions employed in the second period of culturing may be repeated to further activate T lymphocytes in the wells of the wellplate, in a tube, or in the chamber of a fluidic circuit containing device or a microfluidic device having sequestration pens. 
     In some embodiments, the T lymphocytes being activated comprise CD8+ T lymphocytes, such as naïve CD8+ T lymphocytes. In some embodiments, the T lymphocytes being activated are enriched for CD8+ T lymphocytes, such as naïve CD8+ T lymphocytes. Alternatively, in some embodiments, the T lymphocytes being activated comprise CD4+ T lymphocytes, such as naïve CD4+ T lymphocytes. In some embodiments, the T lymphocytes being activated are enriched for CD4+ T lymphocytes, such as naïve CD4+ T lymphocytes. CD4+ T lymphocytes can be used, e.g., if T cells specific for a Class II-restricted antigen are desired. 
     In some embodiments, the method produces activated T lymphocytes that are CD45RO+. In some embodiments, the method produces activated T lymphocytes that are CD28+. In some embodiments, the method produces activated T lymphocytes that are CD28+CD45RO+. In some embodiments, the method produces activated T lymphocytes that are CD197+. In some embodiments, the method produces activated T lymphocytes that are CD127+. In some embodiments, the method produces activated T lymphocytes that are positive for CD28, CD45RO, CD127 and CD197, or at least any combination of three of the foregoing markers, or at least any combination of two of the foregoing markers. The activated T lymphocytes with any of the foregoing phenotypes can further be CD8+. In some embodiments, any of the foregoing phenotypes that is CD28+ comprises a CD28high phenotype. 
     In some embodiments, the method produces a population of T cells comprising antigen-specific T cells, wherein at least 65%, 70%, 75%, 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 98% of the antigen-specific T cells are CD45RO+/CD28High cells, wherein each of the foregoing values can be modified by “about.” Alternatively or in addition, in some embodiments, the method produces a population of T cells wherein at least 1%, 1.5%, 2%, 3,%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% of the T cells are antigen-specific T cells; or wherein 1%-2%, 2%-3%, 3%-4%, 4%-5%, 5%-6%, 6%-7%, 7%-8%, 8%-9%, 9%-10%, 10%-11%, or 11%-12% of the T cells are antigen-specific T cells, wherein each of the foregoing values can be modified by “about.” The content of the population of T cells can be determined on the “crude” product of the method following contact with the antigen-presenting surface and optionally further expansion steps, i.e., before/without enriching or separating product T cells having a particular phenotype. The determination of antigen-specificity and/or T cell marker phenotype can exclude dead cells. 
     In some embodiments, the method provides a population of T cells in which the fraction of T cells that are antigen-specific is increased relative to the starting population. 
     Cells and Compositions. 
     An activated T lymphocyte produced by any method described herein is provided. 
     In some embodiments, the activated T lymphocytes are CD45RO+. In some embodiments, the activated T lymphocytes are CD28+. In some embodiments, the activated T lymphocytes are CD28+CD45RO+. In some embodiments, the activated T lymphocytes are CD197+. In some embodiments, the activated T lymphocytes are CD127+. In some embodiments, the activated T lymphocytes are positive for CD28, CD45RO, CD127 and CD197, at least any combination of three of the foregoing markers, or at least any combination of two of the foregoing markers. The activated T lymphocytes with any of the foregoing phenotypes can further be CD8+. In some embodiments, any of the foregoing phenotypes that is CD28+ comprises a CD28high phenotype. 
     In some embodiments, a population of T cells comprising activated T cells produced by any method described herein is provided. The population can have any of the features described above for T cell populations. 
     In some embodiments, a microfluidic device is provided comprising a population of T cells provided herein. The microfluidic device can be any of the antigen-presenting microfluidic devices or other microfluidic devices (e.g., for performing an antigen-specific cytotoxicity assay) described herein. 
     In some embodiments, a pharmaceutical composition is provided comprising a population of T cells provided herein. The pharmaceutical composition can further comprise, e.g., saline, glucose, and/or Human Serum Albumin The composition may be an aqueous composition and can be provided in frozen or liquid form. A pharmaceutical composition can be provided as a single dose, e.g., within a syringe, and can comprise 10 million, 100 million, 1 billion, or 10 billion cells. The number of cells administered is indication specific, patient specific (e.g., size of patient), and will also vary with the purity and phenotype of the administered cells. 
     Methods of Performing an Antigen-Specific Cytotoxicity Assay. 
     Provided herein is a method of performing an antigen-specific cytotoxicity assay, comprising: loading one or more target cells into a sequestration pen of a microfluidic device; 
     loading one or more T cells in the sequestration pen, such that the one or more T cells can contact the one or more target cells;
 
contacting the target cells with a detectable marker that labels apoptotic cells; and
 
detecting whether the target cells become apoptotic.
 
     The microfluidic device can be any device described herein. The microfluidic device included in a kit for performing an antigen-specific cytotoxicity assay need not comprise an antigen-presenting synthetic surface. The one or more T cells can be produced or activated according to any method described herein for producing or activating such cells. Any type of CD8+ T cell described herein can be used. In some embodiments, the one or more T cells express a chimeric antigen receptor (CAR). In some embodiments, the one or more T cells do not express a CAR. 
     The target cells can express a tumor antigen, such as any of the tumor antigens described herein. In some embodiments, the T cell is specific for the antigen expressed by the target cells. In some embodiments, the target cells are from an immortal cell line and/or are derived from a cancer such as a melanoma, breast cancer, or lung cancer. 
     In some embodiments, a single target cell and/or a single T cell is loaded into the sequestration pen. In some embodiments, a plurality of target cells and/or a plurality of T cells are loaded into the sequestration pen. In some embodiments, the plurality of T cells is a clonal population. In some embodiments, a single T cell and plurality of target cells are loaded into the sequestration pen. 
     Loading cells into the sequestration pen may be performed using gravity, e.g., by tilting the microfluidic device so that cells are pulled gravitationally into the pen. Alternatively, with a microfluidic device having a dielectrophoresis (DEP) configuration, DEP force can be used to load the cells. In some embodiments, the DEP force is activated by structured light. 
     Any suitable marker that labels apoptotic cells can be used. Markers that label apoptotic cells include those that label dead cells distinguishably from live cells, e.g., dyes that do not cross live cell membranes but do cross compromised dead cell membranes, and labels that are dependent on an apoptosis-associated protein or enzymatic activity (e.g., an apoptosis-associated protease) for labeling. In some embodiments, the marker comprises a nucleic acid-binding moiety. In some embodiments, the marker is a fluorogenic or cleavable marker that is activated by cleavage by a protease, such as an apoptosis-associated protease, such as a caspase, e.g., caspase-3. In some embodiments, the marker comprises a binding agent (e.g., antibody) that specifically binds to apoptotic cells and/or apoptotic bodies; the binding agent can further comprise a detectable moiety, such as a fluorophore. 
     The method can comprise detecting whether target cells have become apoptotic one time or periodically, e.g., two, three, or more times. The method can comprise detecting whether target cells have become apoptotic 2 or more hours after contacting the cells with the marker and/or the T cell(s). 
     Kits for Performing an Antigen-Specific Cytotoxicity Assay. 
     Also provided herein are kits for performing an antigen-specific cytotoxicity assay. In some embodiments, the kit comprises a microfluidic device. The microfluidic device can be any of the microfluidic devices described herein. In some embodiments, the microfluidic device is as described above in the section regarding methods for performing an antigen-specific cytotoxicity assay or as set forth in any embodiments disclosed herein. The microfluidic device included in a kit for performing an antigen-specific cytotoxicity assay need not comprise an antigen-presenting synthetic surface. In some embodiments, the kit comprises a reagent for detecting apoptotic cells. In some embodiments, the reagent for detecting apoptotic cells is a detectable marker that labels apoptotic cells as described above in the section regarding methods for performing an antigen-specific cytotoxicity assay or as set forth in any embodiments disclosed herein. 
     Methods of Treatment. 
     Provided herein is a method of treating a subject in need of treating a cancer; including: obtaining a sample comprising T lymphocytes from the subject; separating the T lymphocytes from other cells in the sample; contacting the T lymphocytes with a antigen-presenting synthetic surface including MHC molecules according to any method described herein, where the MHC molecules include an antigen specific for the cancer of the subject; producing a plurality of T lymphocytes activated to be specific against the cancer of the subject; separating the plurality of specific activated T lymphocytes from non-activated T lymphocytes; and, introducing the plurality of specific activated T lymphocytes into the subject. Also provided herein is a plurality of specific activated T lymphocytes for use in treating a cancer, wherein the plurality is prepared by a method including: obtaining a sample comprising T lymphocytes from the subject; separating the T lymphocytes from other cells in the sample; contacting the T lymphocytes with a antigen-presenting synthetic surface including MHC molecules according to any method described herein, where the MHC molecules include an antigen specific for the cancer of the subject; producing a plurality of T lymphocytes activated to be specific against the cancer of the subject; and separating the plurality of specific activated T lymphocytes from non-activated T lymphocytes. Also provided herein is the use of a plurality of specific activated T lymphocytes for the manufacture of a medicament for treating a cancer, wherein the plurality is prepared by a method including: obtaining a sample comprising T lymphocytes from the subject; separating the T lymphocytes from other cells in the sample; contacting the T lymphocytes with a antigen-presenting synthetic surface including MHC molecules according to any method described herein, where the MHC molecules include an antigen specific for the cancer of the subject; producing a plurality of T lymphocytes activated to be specific against the cancer of the subject; and separating the plurality of specific activated T lymphocytes from non-activated T lymphocytes. 
     Also provided is a method of treating a subject in need of treating a cancer; including introducing a plurality of specific activated T lymphocytes into the subject, wherein the plurality of specific activated T lymphocytes were produced by a method described herein. Also provided is a method of treating a subject in need of treating a cancer, including introducing a population of specific activated T lymphocytes described herein into the subject. Such methods can further comprise separating activated T lymphocytes from non-activated T lymphocytes. Also provided is a plurality of specific activated T lymphocytes for use in treating a subject in need of treating a cancer, wherein the plurality of specific activated T lymphocytes were produced by a method described herein. Also provided is a population of specific activated T lymphocytes described herein for use in treating a subject in need of treating a cancer. Also provided is a use of a plurality of specific activated T lymphocytes for the manufacture of a medicament for treating a subject in need of treating a cancer, wherein the plurality of specific activated T lymphocytes were produced by a method described herein. Also provided is a use of a population of specific activated T lymphocytes described herein for the manufacture of a medicament for treating a subject in need of treating a cancer. Such a plurality or population of specific activated T lymphocytes can be further prepared by separating activated T lymphocytes from non-activated T lymphocytes. 
     In some embodiments, separating the plurality of specific activated T lymphocytes may further include detecting surface biomarkers of the specific activated T lymphocytes. 
     In some embodiments, the specific activated T lymphocytes are autologous (i.e., derived from the subject to which they are to be administered). 
     In various embodiments, the methods or the preparation of the plurality or population of specific activated T lymphocytes may further include rapidly expanding the activated T lymphocytes to provide an expanded population of activated T lymphocytes. In some embodiments, the rapid expansion may be performed after separating the specific activated T lymphocytes from the non-activated T lymphocytes. The generation of sufficient levels of T lymphocytes may be achieved using rapid expansion methods described herein or known in the art. See, e.g., the Examples below; Riddell, U.S. Pat. No. 5,827,642; Riddell et al., U.S. Pat. No. 6,040,177, and Yee and Li, PCT Patent App. Pub. No. WO2009/045308 A2. 
     Uses of T cells in treatment of human subjects (e.g., for adoptive cell therapy) are known in the art. T cells prepared according to the methods described herein can be used in such methods. For example, adoptive cell therapy using tumor-infiltrating lymphocytes including MART-1 antigen specific T cells have been tested in the clinic (Powell et al., Blood 105:241-250, 2005). Also, administration of T cells coactivated with anti-CD3 monoclonal antibody and IL-2 was described in Chang et al., J. Clinical Oncology 21:884-890, 2003. Additional examples and/or discussion of T cell administration for the treatment of cancer are provided in Dudley et al.,  Science  298:850-854, 2002; Roszkowski et al.,  Cancer Res  65(4): 1570-76, 2005; Cooper et al.,  Blood  101: 1637-44, 2003; Yee, US Patent App. Pub. No. 2006/0269973; Yee and Li, PCT Patent App. Pub. No. WO2009/045308 A2; Gruenberg et al., US Patent App. Pub. No. 2003/0170238; Rosenberg, U.S. Pat. No. 4,690,915; and Alajez et al., Blood 105:4583-89, 2005. 
     In some embodiments, the cells are formulated by first harvesting them from their culture medium, and then washing and concentrating the cells in a medium and container system suitable for administration (a “pharmaceutically acceptable” carrier) in a treatment-effective amount. Suitable infusion medium can be any isotonic medium formulation, typically normal saline, Normosol R (Abbott) or Plasma-Lyte A (Baxter), but also 5% dextrose in water or Ringer&#39;s lactate can be utilized. The infusion medium can be supplemented with human serum albumin. 
     In some embodiments, the number of cells in the composition is at least 10 9 , or at least 10 19  cells. In some embodiments, a single dose can comprise at least 10 million, 100 million, 1 billion, or 10 billion cells. The number of cells administered is indication specific, patient specific (e.g., size of patient), and will also vary with the purity and phenotype of the administered cells. The number of cells will depend upon the ultimate use for which the composition is intended as will the type of cells included therein. For example, if cells that are specific for a particular antigen are desired, then the population will contain greater than 70%, generally greater than 80%, 85% and 90-95% of such cells. For uses provided herein, the cells are generally in a volume of a liter or less, can be 500 mls or less, even 250 mls or 100 mls or less. Hence the density of the desired cells may be greater than 10 6  cells/ml, greater than 10 7  cells/ml, or 10 8  cells/ml or greater. The clinically relevant number of immune cells can be apportioned into multiple infusions that cumulatively equal or exceed 10 9 ,  10   10  or 10 11  cells. 
     In some embodiments, T lymphocytes described herein or prepared according to a method described herein of the invention may be used to confer immunity to individuals against a tumor or cancer cells. By “immunity” is meant a lessening of one or more physical symptoms associated with cancer cells or a tumor against an antigen of which the lymphocytes have been activated. The cells may be administered by infusion, with each infusion in a range of at least 10 6  to 10 10  cells/m 2 , e.g., in the range of at least 10 7  to 10 9  cells/m 2 . The clones may be administered by a single infusion, or by multiple infusions over a range of time. However, since different individuals are expected to vary in responsiveness, the type and amount of cells infused, as well as the number of infusions and the time range over which multiple infusions are given are determined by the attending physician, and can be determined by examination. 
     Following the transfer of cells back into patients, methods may be employed to maintain their viability by treating patients with cytokines that could include IL-21 and IL-2 (Bear et al.,  Cancer Immunol. Immunother.  50:269-74, 2001; and Schultze et al.,  Br. J. Haematol.  113:455-60, 2001). In another embodiment, cells are cultured in the presence of IL-21 before administration to the patient. See, e.g., Yee, US Patent App. Pub. No. 2006/0269973. IL-21 can increase T cell frequency in a population comprising activated T cells to levels that are high enough for expansion and adoptive transfer without further antigen-specific T cell enrichment. Accordingly, such a step can further decrease the time to therapy and/or obviate a need for further selection and/or cloning. 
     Kits for Preparing an Antigen-Presenting Synthetic Surface. 
     A kit is also provided for preparing an antigen-presenting synthetic surface for activating a T lymphocyte (T cell), including: a. any covalently functionalized synthetic surface as described herein, which includes a plurality of noncovalently or covalently associated first coupling agents; and a first modification reagent including a plurality of major histocompatibility complex (MHC) I molecules configured to bind with a T cell receptor of the T cell, and further wherein the MHC molecules are configured to bind to one of a first subset of the plurality of noncovalently or covalently associated first coupling agents of the covalently functionalized synthetic surface. In some embodiments, the first coupling agents may be a biotin-binding agent. The biotin-binding agent may be streptavidin. In some embodiments, each of the plurality of MHC molecules may further include at least one biotin functionality. Other coupling chemistries may be used, as is known in the art, wherein other site specific protein tags may be attached to the MHC protein, which are configured to covalently attach to recognition protein based species attached to the bead. These coupling strategies can provide the equivalent site specific and specifically orienting attachment of the MHC molecule as provided by C-terminal biotinylation of the MHC molecule. The covalently functionalized synthetic surface may be a wafer, a bead, at least one inner surface of a microfluidic device, or a tube. 
     The kit may further include a reagent including a plurality of co-activating molecules, each configured to bind one of a second subset of the plurality of noncovalently or covalently associated biotin-binding agents of the covalently functionalized synthetic surface. In some embodiments, each of the plurality of co-activating molecules may include a biotin functionality. Each of the co-activating molecules may include a T cell receptor (TCR) co-activating molecule, an adjunct TCR activating molecule, or any combination thereof. In some embodiments, the reagent is provided in individual containers containing the T cell receptor (TCR) co-activating molecule and/or an adjunct TCR activating molecule. Alternatively, the reagent including the plurality of co-activating molecules may be provided in one container containing the TCR co-activating molecules and/or the adjunct TCR activating molecules of the plurality of co-activating molecular ligands in a ratio from about 100:1 to 1:100. In some embodiments the reagent including the plurality of co-activating molecules includes a mixture of TCR co-activating molecules and adjunct TCR activating molecules wherein the ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is 100:1 to 90:1, 90:1 to 80:1, 80:1 to 70:1, 70:1 to 60:1, 60:1 to 50:1, 50:1 to 40:1, 40:1 to 30:1, 30:1 to 20:1, 20:1 to 10:1, 10:1 to 1:1, 1:1 to 1:10, 1:10 to 1:20, 1:20 to 1:30, 1:30 to 1:40, 1:40 to 1:50, 1:50 to 1:60, 1:60 to 1:70, 1:70 to 1:80, 1:80 to 1:90, or 1:90 to 1:100, wherein each of the foregoing values is modified by “about”. In some embodiments, the reagent including a plurality of co-activating molecules contains the TCR co-activating molecules and the adjunct TCR activating molecules of the plurality of co-activating molecular ligands in a ratio from about 20:1 to about 1:20. 
     In some embodiments, the kit for preparing an antigen presenting synthetic surface may further include a reagent including adhesion stimulatory molecules, wherein each adhesion stimulatory molecule includes a ligand for a cell adhesion receptor including an ICAM protein sequence configured to react with a third subset of the plurality of noncovalently or covalently associated biotin-binding agent functionalities of the covalently functionalized synthetic surface. In some embodiments, the adhesion stimulatory molecule may include a biotin functionality. 
     In some embodiments, the kit for preparing an antigen presenting synthetic surface may further include a reagent including growth stimulatory molecules, wherein each growth stimulatory molecule may include a growth factor receptor ligand. In some embodiments, the growth factor receptor ligand may include a cytokine or a fragment thereof. In some embodiments, the cytokine may include IL-21 or a fragment thereof. In some embodiments, the growth stimulatory molecule may be attached to a covalently modified bead. 
     In some embodiments, the kit for preparing an antigen presenting synthetic surface may further include a reagent including one or more additional growth-stimulatory molecules. In some embodiments, the one or more additional growth-stimulatory molecules include IL2 and/or IL7, or fragments thereof. In some embodiments, the growth stimulatory molecule may be attached to a covalently modified bead. 
     Kits for Activating T Lymphocytes. 
     Also provided is a kit for activating T lymphocytes, including an antigen-presenting synthetic surface as described herein. The kit can further comprise growth stimulatory molecules, wherein each growth stimulatory molecule may include a growth factor receptor ligand. The growth stimulatory molecules can be provided as free molecules, attached to the antigen presenting synthetic surface (in the same or a different region than the primary activating molecular ligand), or attached to a different covalently modified synthetic surface. For example, the kit can further comprise a plurality of covalently modified beads comprising an adjunct stimulatory molecule. In some embodiments, the growth factor receptor ligand molecule may include a cytokine or a fragment thereof. In some embodiments, the growth factor receptor ligand may include IL-21. In other embodiments, the kit may include one or more additional (e.g., a second or second and third) growth stimulatory molecules). In some embodiments, the one or more additional growth stimulatory molecules may include IL-2 and/or IL-7, or fragments thereof. Additional growth stimulatory molecules can be provided as a free molecule, attached to the antigen presenting synthetic surface (in the same or a different region than the primary activating molecular ligand), or attached to a different covalently modified synthetic surface, such as a bead. 
     Additional Aspects of Microfluidic Device Structure, Loading, and Operation; Related Systems 
     Microfluidic devices and uses thereof described herein may have any of the following features, and can be used in conjunction with systems described below. 
     Methods of Loading. 
     Loading of biological micro-objects or micro-objects such as, but not limited to, beads, can involve the use of fluid flow, gravity, a dielectrophoresis (DEP) force, electrowetting, a magnetic force, or any combination thereof as described herein. The DEP force can be generated optically, such as by an optoelectronic tweezers (OET) configuration and/or electrically, such as by activation of electrodes/electrode regions in a temporal/spatial pattern. Similarly, electrowetting force may be provided optically, such as by an opto-electro wetting (OEW) configuration and/or electrically, such as by activation of electrodes/electrode regions in a temporal spatial pattern. 
     Microfluidic Devices and Systems for Operating and Observing Such Devices. 
       FIG. 1A  illustrates an example of a microfluidic device  100  and a system  150  which can be used for maintaining, isolating, assaying or culturing biological micro-objects. A perspective view of the microfluidic device  100  is shown having a partial cut-away of its cover  110  to provide a partial view into the microfluidic device  100 . The microfluidic device  100  generally comprises a microfluidic circuit  120  comprising a flow path  106  through which a fluidic medium  180  can flow, optionally carrying one or more micro-objects (not shown) into and/or through the microfluidic circuit  120 . Although a single microfluidic circuit  120  is illustrated in  FIG. 1A , suitable microfluidic devices can include a plurality (e.g., 2 or 3) of such microfluidic circuits. Regardless, the microfluidic device  100  can be configured to be a nanofluidic device. As illustrated in  FIG. 1A , the microfluidic circuit  120  may include a plurality of microfluidic sequestration pens  124 ,  126 ,  128 , and  130 , where each sequestration pens may have one or more openings in fluidic communication with flow path  106 . In some embodiments of the device of  FIG. 1A , the sequestration pens may have only a single opening in fluidic communication with the flow path  106 . As discussed further below, the microfluidic sequestration pens comprise various features and structures that have been optimized for retaining micro-objects in the microfluidic device, such as microfluidic device  100 , even when a medium  180  is flowing through the flow path  106 . Before turning to the foregoing, however, a brief description of microfluidic device  100  and system  150  is provided. 
     As generally illustrated in  FIG. 1A , the microfluidic circuit  120  is defined by an enclosure  102 . Although the enclosure  102  can be physically structured in different configurations, in the example shown in  FIG. 1A  the enclosure  102  is depicted as comprising a support structure  104  (e.g., a base), a microfluidic circuit structure  108 , and a cover  110 . The support structure  104 , microfluidic circuit structure  108 , and cover  110  can be attached to each other. For example, the microfluidic circuit structure  108  can be disposed on an inner surface  109  of the support structure  104 , and the cover  110  can be disposed over the microfluidic circuit structure  108 . Together with the support structure  104  and cover  110 , the microfluidic circuit structure  108  can define the elements of the microfluidic circuit  120 . 
     The support structure  104  can be at the bottom and the cover  110  at the top of the microfluidic circuit  120  as illustrated in  FIG. 1A . Alternatively, the support structure  104  and the cover  110  can be configured in other orientations. For example, the support structure  104  can be at the top and the cover  110  at the bottom of the microfluidic circuit  120 . Regardless, there can be one or more ports  107  each comprising a passage into or out of the enclosure  102 . Examples of a passage include a valve, a gate, a pass-through hole, or the like. As illustrated, port  107  is a pass-through hole created by a gap in the microfluidic circuit structure  108 . However, the port  107  can be situated in other components of the enclosure  102 , such as the cover  110 . Only one port  107  is illustrated in  FIG. 1A  but the microfluidic circuit  120  can have two or more ports  107 . For example, there can be a first port  107  that functions as an inlet for fluid entering the microfluidic circuit  120 , and there can be a second port  107  that functions as an outlet for fluid exiting the microfluidic circuit  120 . Whether a port  107  function as an inlet or an outlet can depend upon the direction that fluid flows through flow path  106 . 
     The support structure  104  can comprise one or more electrodes (not shown) and a substrate or a plurality of interconnected substrates. For example, the support structure  104  can comprise one or more semiconductor substrates, each of which is electrically connected to an electrode (e.g., all or a subset of the semiconductor substrates can be electrically connected to a single electrode). The support structure  104  can further comprise a printed circuit board assembly (“PCBA”). For example, the semiconductor substrate(s) can be mounted on a PCBA. 
     The microfluidic circuit structure  108  can define circuit elements of the microfluidic circuit  120 . Such circuit elements can comprise spaces or regions that can be fluidly interconnected when microfluidic circuit  120  is filled with fluid, such as flow regions (which may include or be one or more flow channels), chambers, pens, traps, and the like. In the microfluidic circuit  120  illustrated in  FIG. 1A , the microfluidic circuit structure  108  comprises a frame  114  and a microfluidic circuit material  116 . The frame  114  can partially or completely enclose the microfluidic circuit material  116 . The frame  114  can be, for example, a relatively rigid structure substantially surrounding the microfluidic circuit material  116 . For example, the frame  114  can comprise a metal material. 
     The microfluidic circuit material  116  can be patterned with cavities or the like to define circuit elements and interconnections of the microfluidic circuit  120 . The microfluidic circuit material  116  can comprise a flexible material, such as a flexible polymer (e.g. rubber, plastic, elastomer, silicone, polydimethylsiloxane (“PDMS”), or the like), which can be gas permeable. Other examples of materials that can compose microfluidic circuit material  116  include molded glass, an etchable material such as silicone (e.g. photo-patternable silicone or “PPS”), photo-resist (e.g., SU8), or the like. In some embodiments, such materials—and thus the microfluidic circuit material  116 —can be rigid and/or substantially impermeable to gas. Regardless, microfluidic circuit material  116  can be disposed on the support structure  104  and inside the frame  114 . 
     The cover  110  can be an integral part of the frame  114  and/or the microfluidic circuit material  116 . Alternatively, the cover  110  can be a structurally distinct element, as illustrated in  FIG. 1A . The cover  110  can comprise the same or different materials than the frame  114  and/or the microfluidic circuit material  116 . Similarly, the support structure  104  can be a separate structure from the frame  114  or microfluidic circuit material  116  as illustrated, or an integral part of the frame  114  or microfluidic circuit material  116 . Likewise, the frame  114  and microfluidic circuit material  116  can be separate structures as shown in  FIG. 1A  or integral portions of the same structure. 
     In some embodiments, the cover  110  can comprise a rigid material. The rigid material may be glass or a material with similar properties. In some embodiments, the cover  110  can comprise a deformable material. The deformable material can be a polymer, such as PDMS. In some embodiments, the cover  110  can comprise both rigid and deformable materials. For example, one or more portions of cover  110  (e.g., one or more portions positioned over sequestration pens  124 ,  126 ,  128 ,  130 ) can comprise a deformable material that interfaces with rigid materials of the cover  110 . In some embodiments, the cover  110  can further include one or more electrodes. The one or more electrodes can comprise a conductive oxide, such as indium-tin-oxide (ITO), which may be coated on glass or a similarly insulating material. Alternatively, the one or more electrodes can be flexible electrodes, such as single-walled nanotubes, multi-walled nanotubes, nanowires, clusters of electrically conductive nanoparticles, or combinations thereof, embedded in a deformable material, such as a polymer (e.g., PDMS). Flexible electrodes that can be used in microfluidic devices have been described, for example, in U.S. 2012/0325665 (Chiou et al.), the contents of which are incorporated herein by reference. In some embodiments, the cover  110  can be modified (e.g., by conditioning all or part of a surface that faces inward toward the microfluidic circuit  120 ) to support cell adhesion, viability and/or growth. The modification may include a coating of a synthetic or natural polymer. In some embodiments, the cover  110  and/or the support structure  104  can be transparent to light. The cover  110  may also include at least one material that is gas permeable (e.g., PDMS or PPS). 
       FIG. 1A  also shows a system  150  for operating and controlling microfluidic devices, such as microfluidic device  100 . System  150  includes an electrical power source  192 , an imaging device (incorporated within imaging module  164 , and not explicitly illustrated in  FIG. 1A ), and a tilting device (part of tilting module  166 , and not explicitly illustrated in  FIG. 1A ). 
     The electrical power source  192  can provide electric power to the microfluidic device  100  and/or tilting device  190 , providing biasing voltages or currents as needed. The electrical power source  192  can, for example, comprise one or more alternating current (AC) and/or direct current (DC) voltage or current sources. The imaging device  194  (part of imaging module  164 , discussed below) can comprise a device, such as a digital camera, for capturing images inside microfluidic circuit  120 . In some instances, the imaging device  194  further comprises a detector having a fast frame rate and/or high sensitivity (e.g. for low light applications). The imaging device  194  can also include a mechanism for directing stimulating radiation and/or light beams into the microfluidic circuit  120  and collecting radiation and/or light beams reflected or emitted from the microfluidic circuit  120  (or micro-objects contained therein). The emitted light beams may be in the visible spectrum and may, e.g., include fluorescent emissions. The reflected light beams may include reflected emissions originating from an LED or a wide spectrum lamp, such as a mercury lamp (e.g. a high pressure mercury lamp) or a Xenon arc lamp. As discussed with respect to  FIG. 3B , the imaging device  194  may further include a microscope (or an optical train), which may or may not include an eyepiece. 
     System  150  further comprises a tilting device  190  (part of tilting module  166 , discussed below) configured to rotate a microfluidic device  100  about one or more axes of rotation. In some embodiments, the tilting device  190  is configured to support and/or hold the enclosure  102  comprising the microfluidic circuit  120  about at least one axis such that the microfluidic device  100  (and thus the microfluidic circuit  120 ) can be held in a level orientation (i.e. at 0° relative to x- and y-axes), a vertical orientation (i.e. at 90° relative to the x-axis and/or the y-axis), or any orientation therebetween. The orientation of the microfluidic device  100  (and the microfluidic circuit  120 ) relative to an axis is referred to herein as the “tilt” of the microfluidic device  100  (and the microfluidic circuit  120 ). For example, the tilting device  190  can tilt the microfluidic device  100  at 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, 1°, 2°, 3°, 4°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 90° relative to the x-axis or any degree therebetween. The level orientation (and thus the x- and y-axes) is defined as normal to a vertical axis defined by the force of gravity. The tilting device can also tilt the microfluidic device  100  (and the microfluidic circuit  120 ) to any degree greater than 90° relative to the x-axis and/or y-axis, or tilt the microfluidic device  100  (and the microfluidic circuit  120 ) 180° relative to the x-axis or the y-axis in order to fully invert the microfluidic device  100  (and the microfluidic circuit  120 ). Similarly, in some embodiments, the tilting device  190  tilts the microfluidic device  100  (and the microfluidic circuit  120 ) about an axis of rotation defined by flow path  106  or some other portion of microfluidic circuit  120 . 
     In some instances, the microfluidic device  100  is tilted into a vertical orientation such that the flow path  106  is positioned above or below one or more sequestration pens. The term “above” as used herein in the context of microfluidic devices denotes that the flow path  106  is positioned higher than the one or more sequestration pens on a vertical axis defined by the force of gravity (i.e. an object in a sequestration pen above a flow path  106  would have a higher gravitational potential energy than an object in the flow path). The term “below” as used herein in the context of microfluidic devices denotes that the flow path  106  is positioned lower than the one or more sequestration pens on a vertical axis defined by the force of gravity (i.e. an object in a sequestration pen below a flow path  106  would have a lower gravitational potential energy than an object in the flow path). 
     In some instances, the tilting device  190  tilts the microfluidic device  100  about an axis that is parallel to the flow path  106 . Moreover, the microfluidic device  100  can be tilted to an angle of less than 90° such that the flow path  106  is located above or below one or more sequestration pens without being located directly above or below the sequestration pens. In other instances, the tilting device  190  tilts the microfluidic device  100  about an axis perpendicular to the flow path  106 . In still other instances, the tilting device  190  tilts the microfluidic device  100  about an axis that is neither parallel nor perpendicular to the flow path  106 . 
     System  150  can further include a media source  178 . The media source  178  (e.g., a container, reservoir, or the like) can comprise multiple sections or containers, each for holding a different fluidic medium  180 . Thus, the media source  178  can be a device that is outside of and separate from the microfluidic device  100 , as illustrated in  FIG. 1A . Alternatively, the media source  178  can be located in whole or in part inside the enclosure  102  of the microfluidic device  100 . For example, the media source  178  can comprise reservoirs that are part of the microfluidic device  100 . 
       FIG. 1A  also illustrates simplified block diagram depictions of examples of control and monitoring equipment  152  that constitute part of system  150  and can be utilized in conjunction with a microfluidic device  100 . As shown, examples of such control and monitoring equipment  152  include a master controller  154  comprising a media module  160  for controlling the media source  178 , a motive module  162  for controlling movement and/or selection of micro-objects (not shown) and/or medium (e.g., droplets of medium) in the microfluidic circuit  120 , an imaging module  164  for controlling an imaging device  194  (e.g., a camera, microscope, light source or any combination thereof) for capturing images (e.g., digital images), and a tilting module  166  for controlling a tilting device  190 . The control equipment  152  can also include other modules  168  for controlling, monitoring, or performing other functions with respect to the microfluidic device  100 . As shown, the equipment  152  can further include a display device  170  and an input/output device  172 . 
     The master controller  154  can comprise a control module  156  and a digital memory  158 . The control module  156  can comprise, for example, a digital processor configured to operate in accordance with machine executable instructions (e.g., software, firmware, source code, or the like) stored as non-transitory data or signals in the memory  158 . Alternatively, or in addition, the control module  156  can comprise hardwired digital circuitry and/or analog circuitry. The media module  160 , motive module  162 , imaging module  164 , tilting module  166 , and/or other modules  168  can be similarly configured. Thus, functions, processes acts, actions, or steps of a process discussed herein as being performed with respect to the microfluidic device  100  or any other microfluidic apparatus can be performed by any one or more of the master controller  154 , media module  160 , motive module  162 , imaging module  164 , tilting module  166 , and/or other modules  168  configured as discussed above. Similarly, the master controller  154 , media module  160 , motive module  162 , imaging module  164 , tilting module  166 , and/or other modules  168  may be communicatively coupled to transmit and receive data used in any function, process, act, action or step discussed herein. 
     The media module  160  controls the media source  178 . For example, the media module  160  can control the media source  178  to input a selected fluidic medium  180  into the enclosure  102  (e.g., through an inlet port  107 ). The media module  160  can also control removal of media from the enclosure  102  (e.g., through an outlet port (not shown)). One or more media can thus be selectively input into and removed from the microfluidic circuit  120 . The media module  160  can also control the flow of fluidic medium  180  in the flow path  106  inside the microfluidic circuit  120 . For example, in some embodiments media module  160  stops the flow of media  180  in the flow path  106  and through the enclosure  102  prior to the tilting module  166  causing the tilting device  190  to tilt the microfluidic device  100  to a desired angle of incline. 
     The motive module  162  can be configured to control selection, trapping, and movement of micro-objects (not shown) in the microfluidic circuit  120 . As discussed below with respect to  FIGS. 1B and 10 , the enclosure  102  can comprise a dielectrophoresis (DEP), optoelectronic tweezers (OET) and/or opto-electrowetting (OEW) configuration (not shown in  FIG. 1A ), and the motive module  162  can control the activation of electrodes and/or transistors (e.g., phototransistors) to select and move micro-objects (not shown) and/or droplets of medium (not shown) in the flow path  106  and/or sequestration pens  124 ,  126 ,  128 ,  130 . 
     The imaging module  164  can control the imaging device  194 . For example, the imaging module  164  can receive and process image data from the imaging device  194 . Image data from the imaging device  194  can comprise any type of information captured by the imaging device  194  (e.g., the presence or absence of micro-objects, droplets of medium, accumulation of label, such as fluorescent label, etc.). Using the information captured by the imaging device  194 , the imaging module  164  can further calculate the position of objects (e.g., micro-objects, droplets of medium) and/or the rate of motion of such objects within the microfluidic device  100 . 
     The tilting module  166  can control the tilting motions of tilting device  190 . Alternatively, or in addition, the tilting module  166  can control the tilting rate and timing to optimize transfer of micro-objects to the one or more sequestration pens via gravitational forces. The tilting module  166  is communicatively coupled with the imaging module  164  to receive data describing the motion of micro-objects and/or droplets of medium in the microfluidic circuit  120 . Using this data, the tilting module  166  may adjust the tilt of the microfluidic circuit  120  in order to adjust the rate at which micro-objects and/or droplets of medium move in the microfluidic circuit  120 . The tilting module  166  may also use this data to iteratively adjust the position of a micro-object and/or droplet of medium in the microfluidic circuit  120 . 
     In the example shown in  FIG. 1A , the microfluidic circuit  120  is illustrated as comprising a microfluidic channel  122  and sequestration pens  124 ,  126 ,  128 ,  130 . Each pen comprises an opening to channel  122 , but otherwise is enclosed such that the pens can substantially isolate micro-objects inside the pen from fluidic medium  180  and/or micro-objects in the flow path  106  of channel  122  or in other pens. The walls of the sequestration pen extend from the inner surface  109  of the base to the inside surface of the cover  110  to provide enclosure. The opening of the pen to the microfluidic channel  122  is oriented at an angle to the flow  106  of fluidic medium  180  such that flow  106  is not directed into the pens. The flow may be tangential or orthogonal to the plane of the opening of the pen. In some instances, pens  124 ,  126 ,  128 ,  130  are configured to physically corral one or more micro-objects within the microfluidic circuit  120 . Sequestration pens in accordance with the present disclosure can comprise various shapes, surfaces and features that are optimized for use with DEP, OET, OEW, fluid flow, and/or gravitational forces, as will be discussed and shown in detail below. 
     The microfluidic circuit  120  may comprise any number of microfluidic sequestration pens. Although five sequestration pens are shown, microfluidic circuit  120  may have fewer or more sequestration pens. As shown, microfluidic sequestration pens  124 ,  126 ,  128 , and  130  of microfluidic circuit  120  each comprise differing features and shapes which may provide one or more benefits useful for maintaining, isolating, assaying or culturing biological micro-objects. In some embodiments, the microfluidic circuit  120  comprises a plurality of identical microfluidic sequestration pens. 
     In the embodiment illustrated in  FIG. 1A , a single channel  122  and flow path  106  is shown. 
     However, other embodiments may contain multiple channels  122 , each configured to comprise a flow path  106 . The microfluidic circuit  120  further comprises an inlet valve or port  107  in fluid communication with the flow path  106  and fluidic medium  180 , whereby fluidic medium  180  can access channel  122  via the inlet port  107 . In some instances, the flow path  106  comprises a single path. In some instances, the single path is arranged in a zigzag pattern whereby the flow path  106  travels across the microfluidic device  100  two or more times in alternating directions. 
     In some instances, microfluidic circuit  120  comprises a plurality of parallel channels  122  and flow paths  106 , wherein the fluidic medium  180  within each flow path  106  flows in the same direction. In some instances, the fluidic medium within each flow path  106  flows in at least one of a forward or reverse direction. In some instances, a plurality of sequestration pens is configured (e.g., relative to a channel  122 ) such that the sequestration pens can be loaded with target micro-objects in parallel. 
     In some embodiments, microfluidic circuit  120  further comprises one or more micro-object traps  132 . The traps  132  are generally formed in a wall forming the boundary of a channel  122 , and may be positioned opposite an opening of one or more of the microfluidic sequestration pens  124 ,  126 ,  128 ,  130 . In some embodiments, the traps  132  are configured to receive or capture a single micro-object from the flow path  106 . In some embodiments, the traps  132  are configured to receive or capture a plurality of micro-objects from the flow path  106 . In some instances, the traps  132  comprise a volume approximately equal to the volume of a single target micro-object. 
     The traps  132  may further comprise an opening which is configured to assist the flow of targeted micro-objects into the traps  132 . In some instances, the traps  132  comprise an opening having a height and width that is approximately equal to the dimensions of a single target micro-object, whereby larger micro-objects are prevented from entering into the micro-object trap. The traps  132  may further comprise other features configured to assist in retention of targeted micro-objects within the trap  132 . In some instances, the trap  132  is aligned with and situated on the opposite side of a channel  122  relative to the opening of a microfluidic sequestration pen, such that upon tilting the microfluidic device  100  about an axis parallel to the microfluidic channel  122 , the trapped micro-object exits the trap  132  at a trajectory that causes the micro-object to fall into the opening of the sequestration pen. In some instances, the trap  132  comprises a side passage  134  that is smaller than the target micro-object in order to facilitate flow through the trap  132  and thereby increase the likelihood of capturing a micro-object in the trap  132 . 
     In some embodiments, dielectrophoretic (DEP) forces are applied across the fluidic medium  180  (e.g., in the flow path and/or in the sequestration pens) via one or more electrodes (not shown) to manipulate, transport, separate and sort micro-objects located therein. For example, in some embodiments, DEP forces are applied to one or more portions of microfluidic circuit  120  in order to transfer a single micro-object from the flow path  106  into a desired microfluidic sequestration pen. In some embodiments, DEP forces are used to prevent a micro-object within a sequestration pen (e.g., sequestration pen  124 ,  126 ,  128 , or  130 ) from being displaced therefrom. Further, in some embodiments, DEP forces are used to selectively remove a micro-object from a sequestration pen that was previously collected in accordance with the embodiments of the current disclosure. In some embodiments, the DEP forces comprise optoelectronic tweezer (OET) forces. 
     In other embodiments, optoelectrowetting (OEW) forces are applied to one or more positions in the support structure  104  (and/or the cover  110 ) of the microfluidic device  100  (e.g., positions helping to define the flow path and/or the sequestration pens) via one or more electrodes (not shown) to manipulate, transport, separate and sort droplets located in the microfluidic circuit  120 . For example, in some embodiments, OEW forces are applied to one or more positions in the support structure  104  (and/or the cover  110 ) in order to transfer a single droplet from the flow path  106  into a desired microfluidic sequestration pen. In some embodiments, OEW forces are used to prevent a droplet within a sequestration pen (e.g., sequestration pen  124 ,  126 ,  128 , or  130 ) from being displaced therefrom. Further, in some embodiments, OEW forces are used to selectively remove a droplet from a sequestration pen that was previously collected in accordance with the embodiments of the current disclosure. 
     In some embodiments, DEP and/or OEW forces are combined with other forces, such as flow and/or gravitational force, so as to manipulate, transport, separate and sort micro-objects and/or droplets within the microfluidic circuit  120 . For example, the enclosure  102  can be tilted (e.g., by tilting device  190 ) to position the flow path  106  and micro-objects located therein above the microfluidic sequestration pens, and the force of gravity can transport the micro-objects and/or droplets into the pens. In some embodiments, the DEP and/or OEW forces can be applied prior to the other forces. In other embodiments, the DEP and/or OEW forces can be applied after the other forces. In still other instances, the DEP and/or OEW forces can be applied at the same time as the other forces or in an alternating manner with the other forces. 
       FIGS. 1B, 1C, and 2A-2H  illustrates various embodiments of microfluidic devices that can be used in the practice of the embodiments of the present disclosure.  FIG. 1B  depicts an embodiment in which the microfluidic device  200  is configured as an optically-actuated electrokinetic device. A variety of optically-actuated electrokinetic devices are known in the art, including devices having an optoelectronic tweezer (OET) configuration and devices having an opto-electrowetting (OEW) configuration. Examples of suitable OET configurations are illustrated in the following U.S. patent documents, each of which is incorporated herein by reference in its entirety: U.S. Pat. No. RE 44,711 (Wu et al.) (originally issued as U.S. Pat. No. 7,612,355); and U.S. Pat. No. 7,956,339 (Ohta et al.). Examples of OEW configurations are illustrated in U.S. Pat. No. 6,958,132 (Chiou et al.) and U.S. Patent Application Publication No. 2012/0024708 (Chiou et al.), both of which are incorporated by reference herein in their entirety. Yet another example of an optically-actuated electrokinetic device includes a combined OET/OEW configuration, examples of which are shown in U.S. Patent Publication Nos. 20150306598 (Khandros et al.) and 20150306599 (Khandros et al.) and their corresponding PCT Publications WO2015/164846 and WO2015/164847, all of which are incorporated herein by reference in their entirety. 
     Examples of microfluidic devices having pens in which biological micro-objects can be placed, cultured, and/or monitored have been described, for example, in US 2014/0116881 (application Ser. No. 14/060,117, filed Oct. 22, 2013), US 2015/0151298 (application Ser. No. 14/520,568, filed Oct. 22, 2014), and US 2015/0165436 (application Ser. No. 14/521,447, filed Oct. 22, 2014), each of which is incorporated herein by reference in its entirety. U.S. application Ser. Nos. 14/520,568 and 14/521,447 also describe exemplary methods of analyzing secretions of cells cultured in a microfluidic device. Each of the foregoing applications further describes microfluidic devices configured to produce dielectrophoretic (DEP) forces, such as optoelectronic tweezers (OET) or configured to provide opto-electro wetting (OEW). For example, the optoelectronic tweezers device illustrated in FIG. 2 of US 2014/0116881 is an example of a device that can be utilized in embodiments of the present disclosure to select and move an individual biological micro-object or a group of biological micro-objects. 
     Microfluidic Device Motive Configurations. 
     As described above, the control and monitoring equipment of the system can comprise a motive module for selecting and moving objects, such as micro-objects or droplets, in the microfluidic circuit of a microfluidic device. The microfluidic device can have a variety of motive configurations, depending upon the type of object being moved and other considerations. For example, a dielectrophoresis (DEP) configuration can be utilized to select and move micro-objects in the microfluidic circuit. Thus, the support structure  104  and/or cover  110  of the microfluidic device  100  can comprise a DEP configuration for selectively inducing DEP forces on micro-objects in a fluidic medium  180  in the microfluidic circuit  120  and thereby select, capture, and/or move individual micro-objects or groups of micro-objects. Alternatively, the support structure  104  and/or cover  110  of the microfluidic device  100  can comprise an electrowetting (EW) configuration for selectively inducing EW forces on droplets in a fluidic medium  180  in the microfluidic circuit  120  and thereby select, capture, and/or move individual droplets or groups of droplets. 
     One example of a microfluidic device  200  comprising a DEP configuration is illustrated in  FIGS. 1B and 10 . While for purposes of simplicity  FIGS. 1B and 10  show a side cross-sectional view and a top cross-sectional view, respectively, of a portion of an enclosure  102  of the microfluidic device  200  having a region/chamber  202 , it should be understood that the region/chamber  202  may be part of a fluidic circuit element having a more detailed structure, such as a growth chamber, a sequestration pen, a flow region, or a flow channel. Furthermore, the microfluidic device  200  may include other fluidic circuit elements. For example, the microfluidic device  200  can include a plurality of growth chambers or sequestration pens and/or one or more flow regions or flow channels, such as those described herein with respect to microfluidic device  100 . A DEP configuration may be incorporated into any such fluidic circuit elements of the microfluidic device  200 , or select portions thereof. It should be further appreciated that any of the above or below described microfluidic device components and system components may be incorporated in and/or used in combination with the microfluidic device  200 . For example, system  150  including control and monitoring equipment  152 , described above, may be used with microfluidic device  200 , including one or more of the media module  160 , motive module  162 , imaging module  164 , tilting module  166 , and other modules  168 . 
     As seen in  FIG. 1B , the microfluidic device  200  includes a support structure  104  having a bottom electrode  204  and an electrode activation substrate  206  overlying the bottom electrode  204 , and a cover  110  having a top electrode  210 , with the top electrode  210  spaced apart from the bottom electrode  204 . The top electrode  210  and the electrode activation substrate  206  define opposing surfaces of the region/chamber  202 . A medium  180  contained in the region/chamber  202  thus provides a resistive connection between the top electrode  210  and the electrode activation substrate  206 . A power source  212  configured to be connected to the bottom electrode  204  and the top electrode  210  and create a biasing voltage between the electrodes, as required for the generation of DEP forces in the region/chamber  202 , is also shown. The power source  212  can be, for example, an alternating current (AC) power source. 
     In certain embodiments, the microfluidic device  200  illustrated in  FIGS. 1B and 10  can have an optically-actuated DEP configuration. Accordingly, changing patterns of light  218  from the light source  216 , which may be controlled by the motive module  162 , can selectively activate and deactivate changing patterns of DEP electrodes at regions  214  of the inner surface  208  of the electrode activation substrate  206 . (Hereinafter the regions  214  of a microfluidic device having a DEP configuration are referred to as “DEP electrode regions.”) As illustrated in  FIG. 10 , a light pattern  218  directed onto the inner surface  208  of the electrode activation substrate  206  can illuminate select DEP electrode regions  214   a  (shown in white) in a pattern, such as a square. The non-illuminated DEP electrode regions  214  (cross-hatched) are hereinafter referred to as “dark” DEP electrode regions  214 . The relative electrical impedance through the DEP electrode activation substrate  206  (i.e., from the bottom electrode  204  up to the inner surface  208  of the electrode activation substrate  206  which interfaces with the medium  180  in the flow region  106 ) is greater than the relative electrical impedance through the medium  180  in the region/chamber  202  (i.e., from the inner surface  208  of the electrode activation substrate  206  to the top electrode  210  of the cover  110 ) at each dark DEP electrode region  214 . An illuminated DEP electrode region  214   a , however, exhibits a reduced relative impedance through the electrode activation substrate  206  that is less than the relative impedance through the medium  180  in the region/chamber  202  at each illuminated DEP electrode region  214   a.    
     With the power source  212  activated, the foregoing DEP configuration creates an electric field gradient in the fluidic medium  180  between illuminated DEP electrode regions  214   a  and adjacent dark DEP electrode regions  214 , which in turn creates local DEP forces that attract or repel nearby micro-objects (not shown) in the fluidic medium  180 . DEP electrodes that attract or repel micro-objects in the fluidic medium  180  can thus be selectively activated and deactivated at many different such DEP electrode regions  214  at the inner surface  208  of the region/chamber  202  by changing light patterns  218  projected from a light source  216  into the microfluidic device  200 . Whether the DEP forces attract or repel nearby micro-objects can depend on such parameters as the frequency of the power source  212  and the dielectric properties of the medium  180  and/or micro-objects (not shown). 
     The square pattern  220  of illuminated DEP electrode regions  214   a  illustrated in  FIG. 10  is an example only. Any pattern of the DEP electrode regions  214  can be illuminated (and thereby activated) by the pattern of light  218  projected into the microfluidic device  200 , and the pattern of illuminated/activated DEP electrode regions  214  can be repeatedly changed by changing or moving the light pattern  218 . 
     In some embodiments, the electrode activation substrate  206  can comprise or consist of a photoconductive material. In such embodiments, the inner surface  208  of the electrode activation substrate  206  can be featureless. For example, the electrode activation substrate  206  can comprise or consist of a layer of hydrogenated amorphous silicon (a-Si:H). The a-Si:H can comprise, for example, about 8% to 40% hydrogen (calculated as 100*the number of hydrogen atoms/the total number of hydrogen and silicon atoms). The layer of a-Si:H can have a thickness of about 500 nm to about 2.0 μm. In such embodiments, the DEP electrode regions  214  can be created anywhere and in any pattern on the inner surface  208  of the electrode activation substrate  206 , in accordance with the light pattern  218 . The number and pattern of the DEP electrode regions  214  thus need not be fixed, but can correspond to the light pattern  218 . Examples of microfluidic devices having a DEP configuration comprising a photoconductive layer such as discussed above have been described, for example, in U.S. Pat. No. RE 44,711 (Wu et al.) (originally issued as U.S. Pat. No. 7,612,355), the entire contents of which are incorporated herein by reference. 
     In other embodiments, the electrode activation substrate  206  can comprise a substrate comprising a plurality of doped layers, electrically insulating layers (or regions), and electrically conductive layers that form semiconductor integrated circuits, such as is known in semiconductor fields. For example, the electrode activation substrate  206  can comprise a plurality of phototransistors, including, for example, lateral bipolar phototransistors, each phototransistor corresponding to a DEP electrode region  214 . Alternatively, the electrode activation substrate  206  can comprise electrodes (e.g., conductive metal electrodes) controlled by phototransistor switches, with each such electrode corresponding to a DEP electrode region  214 . The electrode activation substrate  206  can include a pattern of such phototransistors or phototransistor-controlled electrodes. The pattern, for example, can be an array of substantially square phototransistors or phototransistor-controlled electrodes arranged in rows and columns, such as shown in  FIG. 2B . Alternatively, the pattern can be an array of substantially hexagonal phototransistors or phototransistor-controlled electrodes that form a hexagonal lattice. Regardless of the pattern, electric circuit elements can form electrical connections between the DEP electrode regions  214  at the inner surface  208  of the electrode activation substrate  206  and the bottom electrode  210 , and those electrical connections (i.e., phototransistors or electrodes) can be selectively activated and deactivated by the light pattern  218 . When not activated, each electrical connection can have high impedance such that the relative impedance through the electrode activation substrate  206  (i.e., from the bottom electrode  204  to the inner surface  208  of the electrode activation substrate  206  which interfaces with the medium  180  in the region/chamber  202 ) is greater than the relative impedance through the medium  180  (i.e., from the inner surface  208  of the electrode activation substrate  206  to the top electrode  210  of the cover  110 ) at the corresponding DEP electrode region  214 . When activated by light in the light pattern  218 , however, the relative impedance through the electrode activation substrate  206  is less than the relative impedance through the medium  180  at each illuminated DEP electrode region  214 , thereby activating the DEP electrode at the corresponding DEP electrode region  214  as discussed above. DEP electrodes that attract or repel micro-objects (not shown) in the medium  180  can thus be selectively activated and deactivated at many different DEP electrode regions  214  at the inner surface  208  of the electrode activation substrate  206  in the region/chamber  202  in a manner determined by the light pattern  218 . 
     Examples of microfluidic devices having electrode activation substrates that comprise phototransistors have been described, for example, in U.S. Pat. No. 7,956,339 (Ohta et al.) (see, e.g., device  300  illustrated in  FIGS. 21 and 22 , and descriptions thereof), the entire contents of which are incorporated herein by reference. Examples of microfluidic devices having electrode activation substrates that comprise electrodes controlled by phototransistor switches have been described, for example, in U.S. Patent Publication No. 2014/0124370 (Short et al.) (see, e.g., devices  200 ,  400 ,  500 ,  600 , and  900  illustrated throughout the drawings, and descriptions thereof), the entire contents of which are incorporated herein by reference. 
     In some embodiments of a DEP configured microfluidic device, the top electrode  210  is part of a first wall (or cover  110 ) of the enclosure  102 , and the electrode activation substrate  206  and bottom electrode  204  are part of a second wall (or support structure  104 ) of the enclosure  102 . The region/chamber  202  can be between the first wall and the second wall. In other embodiments, the electrode  210  is part of the second wall (or support structure  104 ) and one or both of the electrode activation substrate  206  and/or the electrode  210  are part of the first wall (or cover  110 ). Moreover, the light source  216  can alternatively be used to illuminate the enclosure  102  from below. 
     With the microfluidic device  200  of  FIGS. 1B-1C  having a DEP configuration, the motive module  162  can select a micro-object (not shown) in the medium  180  in the region/chamber  202  by projecting a light pattern  218  into the microfluidic device  200  to activate a first set of one or more DEP electrodes at DEP electrode regions  214   a  of the inner surface  208  of the electrode activation substrate  206  in a pattern (e.g., square pattern  220 ) that surrounds and captures the micro-object. The motive module  162  can then move the in situ-generated captured micro-object by moving the light pattern  218  relative to the microfluidic device  200  to activate a second set of one or more DEP electrodes at DEP electrode regions  214 . Alternatively, the microfluidic device  200  can be moved relative to the light pattern  218 . 
     In other embodiments, the microfluidic device  200  can have a DEP configuration that does not rely upon light activation of DEP electrodes at the inner surface  208  of the electrode activation substrate  206 . For example, the electrode activation substrate  206  can comprise selectively addressable and energizable electrodes positioned opposite to a surface including at least one electrode (e.g., cover  110 ). Switches (e.g., transistor switches in a semiconductor substrate) may be selectively opened and closed to activate or inactivate DEP electrodes at DEP electrode regions  214 , thereby creating a net DEP force on a micro-object (not shown) in region/chamber  202  in the vicinity of the activated DEP electrodes. Depending on such characteristics as the frequency of the power source  212  and the dielectric properties of the medium (not shown) and/or micro-objects in the region/chamber  202 , the DEP force can attract or repel a nearby micro-object. By selectively activating and deactivating a set of DEP electrodes (e.g., at a set of DEP electrodes regions  214  that forms a square pattern  220 ), one or more micro-objects in region/chamber  202  can be trapped and moved within the region/chamber  202 . The motive module  162  in  FIG. 1A  can control such switches and thus activate and deactivate individual ones of the DEP electrodes to select, trap, and move particular micro-objects (not shown) around the region/chamber  202 . Microfluidic devices having a DEP configuration that includes selectively addressable and energizable electrodes are known in the art and have been described, for example, in U.S. Pat. No. 6,294,063 (Becker et al.) and U.S. Pat. No. 6,942,776 (Medoro), the entire contents of which are incorporated herein by reference. 
     As yet another example, the microfluidic device  200  can have an electrowetting (EW) configuration, which can be in place of the DEP configuration or can be located in a portion of the microfluidic device  200  that is separate from the portion which has the DEP configuration. The EW configuration can be an opto-electrowetting configuration or an electrowetting on dielectric (EWOD) configuration, both of which are known in the art. In some EW configurations, the support structure  104  has an electrode activation substrate  206  sandwiched between a dielectric layer (not shown) and the bottom electrode  204 . The dielectric layer can comprise a hydrophobic material and/or can be coated with a hydrophobic material, as described below. For microfluidic devices  200  that have an EW configuration, the inner surface  208  of the support structure  104  is the inner surface of the dielectric layer or its hydrophobic coating. 
     The dielectric layer (not shown) can comprise one or more oxide layers, and can have a thickness of about 50 nm to about 250 nm (e.g., about 125 nm to about 175 nm). In certain embodiments, the dielectric layer may comprise a layer of oxide, such as a metal oxide (e.g., aluminum oxide or hafnium oxide). In certain embodiments, the dielectric layer can comprise a dielectric material other than a metal oxide, such as silicon oxide or a nitride. Regardless of the exact composition and thickness, the dielectric layer can have an impedance of about 10 kOhms to about 50 kOhms. 
     In some embodiments, the surface of the dielectric layer that faces inward toward region/chamber  202  is coated with a hydrophobic material. The hydrophobic material can comprise, for example, fluorinated carbon molecules. Examples of fluorinated carbon molecules include perfluoro-polymers such as polytetrafluoroethylene (e.g., TEFLON®) or poly(2,3-difluoromethylenyl-perfluorotetrahydrofuran) (e.g., CYTOP™). Molecules that make up the hydrophobic material can be covalently bonded to the surface of the dielectric layer. For example, molecules of the hydrophobic material can be covalently bound to the surface of the dielectric layer by means of a linker such as a siloxane group, a phosphonic acid group, or a thiol group. Thus, in some embodiments, the hydrophobic material can comprise alkyl-terminated siloxane, alkyl-termination phosphonic acid, or alkyl-terminated thiol. The alkyl group can be long-chain hydrocarbons (e.g., having a chain of at least 10 carbons, or at least 16, 18, 20, 22, or more carbons). Alternatively, fluorinated (or perfluorinated) carbon chains can be used in place of the alkyl groups. Thus, for example, the hydrophobic material can comprise fluoroalkyl-terminated siloxane, fluoroalkyl-terminated phosphonic acid, or fluoroalkyl-terminated thiol. In some embodiments, the hydrophobic coating has a thickness of about 10 nm to about 50 nm. In other embodiments, the hydrophobic coating has a thickness of less than 10 nm (e.g., less than 5 nm, or about 1.5 to 3.0 nm). 
     In some embodiments, the cover  110  of a microfluidic device  200  having an electrowetting configuration is coated with a hydrophobic material (not shown) as well. The hydrophobic material can be the same hydrophobic material used to coat the dielectric layer of the support structure  104 , and the hydrophobic coating can have a thickness that is substantially the same as the thickness of the hydrophobic coating on the dielectric layer of the support structure  104 . Moreover, the cover  110  can comprise an electrode activation substrate  206  sandwiched between a dielectric layer and the top electrode  210 , in the manner of the support structure  104 . The electrode activation substrate  206  and the dielectric layer of the cover  110  can have the same composition and/or dimensions as the electrode activation substrate  206  and the dielectric layer of the support structure  104 . Thus, the microfluidic device  200  can have two electrowetting surfaces. 
     In some embodiments, the electrode activation substrate  206  can comprise a photoconductive material, such as described above. Accordingly, in certain embodiments, the electrode activation substrate  206  can comprise or consist of a layer of hydrogenated amorphous silicon (a-Si:H). The a-Si:H can comprise, for example, about 8% to 40% hydrogen (calculated as 100*the number of hydrogen atoms/the total number of hydrogen and silicon atoms). The layer of a-Si:H can have a thickness of about 500 nm to about 2.0 μm. Alternatively, the electrode activation substrate  206  can comprise electrodes (e.g., conductive metal electrodes) controlled by phototransistor switches, as described above. Microfluidic devices having an opto-electrowetting configuration are known in the art and/or can be constructed with electrode activation substrates known in the art. For example, U.S. Pat. No. 6,958,132 (Chiou et al.), the entire contents of which are incorporated herein by reference, discloses opto-electrowetting configurations having a photoconductive material such as a-Si:H, while U.S. Patent Publication No. 2014/0124370 (Short et al.), referenced above, discloses electrode activation substrates having electrodes controlled by phototransistor switches. 
     The microfluidic device  200  thus can have an opto-electrowetting configuration, and light patterns  218  can be used to activate photoconductive EW regions or photoresponsive EW electrodes in the electrode activation substrate  206 . Such activated EW regions or EW electrodes of the electrode activation substrate  206  can generate an electrowetting force at the inner surface  208  of the support structure  104  (i.e., the inner surface of the overlaying dielectric layer or its hydrophobic coating). By changing the light patterns  218  (or moving microfluidic device  200  relative to the light source  216 ) incident on the electrode activation substrate  206 , droplets (e.g., containing an aqueous medium, solution, or solvent) contacting the inner surface  208  of the support structure  104  can be moved through an immiscible fluid (e.g., an oil medium) present in the region/chamber  202 . 
     In other embodiments, microfluidic devices  200  can have an EWOD configuration, and the electrode activation substrate  206  can comprise selectively addressable and energizable electrodes that do not rely upon light for activation. The electrode activation substrate  206  thus can include a pattern of such electrowetting (EW) electrodes. The pattern, for example, can be an array of substantially square EW electrodes arranged in rows and columns, such as shown in  FIG. 2B . Alternatively, the pattern can be an array of substantially hexagonal EW electrodes that form a hexagonal lattice. Regardless of the pattern, the EW electrodes can be selectively activated (or deactivated) by electrical switches (e.g., transistor switches in a semiconductor substrate). By selectively activating and deactivating EW electrodes in the electrode activation substrate  206 , droplets (not shown) contacting the inner surface  208  of the overlaying dielectric layer or its hydrophobic coating can be moved within the region/chamber  202 . The motive module  162  in  FIG. 1A  can control such switches and thus activate and deactivate individual EW electrodes to select and move particular droplets around region/chamber  202 . Microfluidic devices having a EWOD configuration with selectively addressable and energizable electrodes are known in the art and have been described, for example, in U.S. Pat. No. 8,685,344 (Sundarsan et al.), the entire contents of which are incorporated herein by reference. 
     Regardless of the configuration of the microfluidic device  200 , a power source  212  can be used to provide a potential (e.g., an AC voltage potential) that powers the electrical circuits of the microfluidic device  200 . The power source  212  can be the same as, or a component of, the power source  192  referenced in FIG.  1 . Power source  212  can be configured to provide an AC voltage and/or current to the top electrode  210  and the bottom electrode  204 . For an AC voltage, the power source  212  can provide a frequency range and an average or peak power (e.g., voltage or current) range sufficient to generate net DEP forces (or electrowetting forces) strong enough to trap and move individual micro-objects (not shown) in the region/chamber  202 , as discussed above, and/or to change the wetting properties of the inner surface  208  of the support structure  104  (i.e., the dielectric layer and/or the hydrophobic coating on the dielectric layer) in the region/chamber  202 , as also discussed above. Such frequency ranges and average or peak power ranges are known in the art. See, e.g., U.S. Pat. No. 6,958,132 (Chiou et al.), U.S. Pat. No. RE44,711 (Wu et al.) (originally issued as U.S. Pat. No. 7,612,355), and US Patent Application Publication Nos. US2014/0124370 (Short et al.), US2015/0306598 (Khandros et al.), and US2015/0306599 (Khandros et al.). 
     Sequestration Pens. 
     Non-limiting examples of generic sequestration pens  224 ,  226 , and  228  are shown within the microfluidic device  230  depicted in  FIGS. 2A-2C . Each sequestration pen  224 ,  226 , and  228  can comprise an isolation structure  232  defining an isolation region  240  and a connection region  236  fluidically connecting the isolation region  240  to a channel  122 . The connection region  236  can comprise a proximal opening  234  to the microfluidic channel  122  and a distal opening  238  to the isolation region  240 . The connection region  236  can be configured so that the maximum penetration depth of a flow of a fluidic medium (not shown) flowing from the microfluidic channel  122  into the sequestration pen  224 ,  226 ,  228  does not extend into the isolation region  240 . Thus, due to the connection region  236 , a micro-object (not shown) or other material (not shown) disposed in an isolation region  240  of a sequestration pen  224 ,  226 ,  228  can thus be isolated from, and not substantially affected by, a flow of medium  180  in the microfluidic channel  122 . 
     The sequestration pens  224 ,  226 , and  228  of  FIGS. 2A-2C  each have a single opening which opens directly to the microfluidic channel  122 . The opening of the sequestration pen opens laterally from the microfluidic channel  122 . The electrode activation substrate  206  underlays both the microfluidic channel  122  and the sequestration pens  224 ,  226 , and  228 . The upper surface of the electrode activation substrate  206  within the enclosure of a sequestration pen, forming the floor of the sequestration pen, is disposed at the same level or substantially the same level of the upper surface the of electrode activation substrate  206  within the microfluidic channel  122  (or flow region if a channel is not present), forming the floor of the flow channel (or flow region, respectively) of the microfluidic device. The electrode activation substrate  206  may be featureless or may have an irregular or patterned surface that varies from its highest elevation to its lowest depression by less than about 3 microns, 2.5 microns, 2 microns, 1.5 microns, 1 micron, 0.9 microns, 0.5 microns, 0.4 microns, 0.2 microns, 0.1 microns or less. The variation of elevation in the upper surface of the substrate across both the microfluidic channel  122  (or flow region) and sequestration pens may be less than about 3%, 2%, 1%. 0.9%, 0.8%, 0.5%, 0.3% or 0.1% of the height of the walls of the sequestration pen or walls of the microfluidic device. While described in detail for the microfluidic device  200 , this also applies to any of the microfluidic devices  100 ,  230 ,  250 ,  280 ,  290  described herein. 
     The microfluidic channel  122  can thus be an example of a swept region, and the isolation regions  240  of the sequestration pens  224 ,  226 ,  228  can be examples of unswept regions. As noted, the microfluidic channel  122  and sequestration pens  224 ,  226 ,  228  can be configured to contain one or more fluidic media  180 . In the example shown in  FIGS. 2A-2B , the ports  222  are connected to the microfluidic channel  122  and allow a fluidic medium  180  to be introduced into or removed from the microfluidic device  230 . Prior to introduction of the fluidic medium  180 , the microfluidic device may be primed with a gas such as carbon dioxide gas. Once the microfluidic device  230  contains the fluidic medium  180 , the flow  242  of fluidic medium  180  in the microfluidic channel  122  can be selectively generated and stopped. For example, as shown, the ports  222  can be disposed at different locations (e.g., opposite ends) of the microfluidic channel  122 , and a flow  242  of medium can be created from one port  222  functioning as an inlet to another port  222  functioning as an outlet. 
       FIG. 2C  illustrates a detailed view of an example of a sequestration pen  224  according to the present disclosure. Examples of micro-objects  246  are also shown. 
     As is known, a flow  242  of fluidic medium  180  in a microfluidic channel  122  past a proximal opening  234  of sequestration pen  224  can cause a secondary flow  244  of the medium  180  into and/or out of the sequestration pen  224 . To isolate micro-objects  246  in the isolation region  240  of a sequestration pen  224  from the secondary flow  244 , the length L con  of the connection region  236  of the sequestration pen  224  (i.e., from the proximal opening  234  to the distal opening  238 ) should be greater than the penetration depth D p  of the secondary flow  244  into the connection region  236 . The penetration depth D p  of the secondary flow  244  depends upon the velocity of the fluidic medium  180  flowing in the microfluidic channel  122  and various parameters relating to the configuration of the microfluidic channel  122  and the proximal opening  234  of the connection region  236  to the microfluidic channel  122 . For a given microfluidic device, the configurations of the microfluidic channel  122  and the opening  234  will be fixed, whereas the rate of flow  242  of fluidic medium  180  in the microfluidic channel  122  will be variable. Accordingly, for each sequestration pen  224 , a maximal velocity V max  for the flow  242  of fluidic medium  180  in channel  122  can be identified that ensures that the penetration depth D p  of the secondary flow  244  does not exceed the length L con  of the connection region  236 . As long as the rate of the flow  242  of fluidic medium  180  in the microfluidic channel  122  does not exceed the maximum velocity V max , the resulting secondary flow  244  can be limited to the microfluidic channel  122  and the connection region  236  and kept out of the isolation region  240 . The flow  242  of medium  180  in the microfluidic channel  122  will thus not draw micro-objects  246  out of the isolation region  240 . Rather, micro-objects  246  located in the isolation region  240  will stay in the isolation region  240  regardless of the flow  242  of fluidic medium  180  in the microfluidic channel  122 . 
     Moreover, as long as the rate of flow  242  of medium  180  in the microfluidic channel  122  does not exceed V max , the flow  242  of fluidic medium  180  in the microfluidic channel  122  will not move miscellaneous particles (e.g., microparticles and/or nanoparticles) from the microfluidic channel  122  into the isolation region  240  of a sequestration pen  224 . Having the length L con  of the connection region  236  be greater than the maximum penetration depth D p  of the secondary flow  244  can thus prevent contamination of one sequestration pen  224  with miscellaneous particles from the microfluidic channel  122  or another sequestration pen (e.g., sequestration pens  226 ,  228  in  FIG. 2D ). 
     Because the microfluidic channel  122  and the connection regions  236  of the sequestration pens  224 ,  226 ,  228  can be affected by the flow  242  of medium  180  in the microfluidic channel  122 , the microfluidic channel  122  and connection regions  236  can be deemed swept (or flow) regions of the microfluidic device  230 . The isolation regions  240  of the sequestration pens  224 ,  226 ,  228 , on the other hand, can be deemed unswept (or non-flow) regions. For example, components (not shown) in a first fluidic medium  180  in the microfluidic channel  122  can mix with a second fluidic medium  248  in the isolation region  240  substantially only by diffusion of components of the first medium  180  from the microfluidic channel  122  through the connection region  236  and into the second fluidic medium  248  in the isolation region  240 . Similarly, components (not shown) of the second medium  248  in the isolation region  240  can mix with the first medium  180  in the microfluidic channel  122  substantially only by diffusion of components of the second medium  248  from the isolation region  240  through the connection region  236  and into the first medium  180  in the microfluidic channel  122 . In some embodiments, the extent of fluidic medium exchange between the isolation region of a sequestration pen and the flow region by diffusion is greater than about 90%, 91%, 92%, 93%, 94% 95%, 96%, 97%, 98%, or greater than about 99% of fluidic exchange. The first medium  180  can be the same medium or a different medium than the second medium  248 . Moreover, the first medium  180  and the second medium  248  can start out being the same, then become different (e.g., through conditioning of the second medium  248  by one or more cells in the isolation region  240 , or by changing the medium  180  flowing through the microfluidic channel  122 ). 
     The maximum penetration depth D p  of the secondary flow  244  caused by the flow  242  of fluidic medium  180  in the microfluidic channel  122  can depend on a number of parameters, as mentioned above. Examples of such parameters include: the shape of the microfluidic channel  122  (e.g., the microfluidic channel can direct medium into the connection region  236 , divert medium away from the connection region  236 , or direct medium in a direction substantially perpendicular to the proximal opening  234  of the connection region  236  to the microfluidic channel  122 ); a width W ch  (or cross-sectional area) of the microfluidic channel  122  at the proximal opening  234 ; and a width W con  (or cross-sectional area) of the connection region  236  at the proximal opening  234 ; the velocity V of the flow  242  of fluidic medium  180  in the microfluidic channel  122 ; the viscosity of the first medium  180  and/or the second medium  248 , or the like. 
     In some embodiments, the dimensions of the microfluidic channel  122  and sequestration pens  224 ,  226 ,  228  can be oriented as follows with respect to the vector of the flow  242  of fluidic medium  180  in the microfluidic channel  122 : the microfluidic channel width W ch  (or cross-sectional area of the microfluidic channel  122 ) can be substantially perpendicular to the flow  242  of medium  180 ; the width W con  (or cross-sectional area) of the connection region  236  at opening  234  can be substantially parallel to the flow  242  of medium  180  in the microfluidic channel  122 ; and/or the length L con  of the connection region can be substantially perpendicular to the flow  242  of medium  180  in the microfluidic channel  122 . The foregoing are examples only, and the relative position of the microfluidic channel  122  and sequestration pens  224 ,  226 ,  228  can be in other orientations with respect to each other. 
     As illustrated in  FIG. 2C , the width W con  of the connection region  236  can be uniform from the proximal opening  234  to the distal opening  238 . The width W con  of the connection region  236  at the distal opening  238  can thus be any of the values identified herein for the width W con  of the connection region  236  at the proximal opening  234 . Alternatively, the width W con  of the connection region  236  at the distal opening  238  can be larger than the width W con  of the connection region  236  at the proximal opening  234 . 
     As illustrated in  FIG. 2C , the width of the isolation region  240  at the distal opening  238  can be substantially the same as the width W con  of the connection region  236  at the proximal opening  234 . The width of the isolation region  240  at the distal opening  238  can thus be any of the values identified herein for the width W con  of the connection region  236  at the proximal opening  234 . Alternatively, the width of the isolation region  240  at the distal opening  238  can be larger or smaller than the width W con  of the connection region  236  at the proximal opening  234 . Moreover, the distal opening  238  may be smaller than the proximal opening  234  and the width W con  of the connection region  236  may be narrowed between the proximal opening  234  and distal opening  238 . For example, the connection region  236  may be narrowed between the proximal opening and the distal opening, using a variety of different geometries (e.g. chamfering the connection region, beveling the connection region). Further, any part or subpart of the connection region  236  may be narrowed (e.g. a portion of the connection region adjacent to the proximal opening  234 ). 
       FIGS. 2D-2F  depict another exemplary embodiment of a microfluidic device  250  containing a microfluidic circuit  262  and flow channels  264 , which are variations of the respective microfluidic device  100 , circuit  132  and channel  134  of  FIG. 1A . The microfluidic device  250  also has a plurality of sequestration pens  266  that are additional variations of the above-described sequestration pens  124 ,  126 ,  128 ,  130 ,  224 ,  226  or  228 . In particular, it should be appreciated that the sequestration pens  266  of device  250  shown in  FIGS. 2D-2F  can replace any of the above-described sequestration pens  124 ,  126 ,  128 ,  130 ,  224 ,  226  or  228  in devices  100 ,  200 ,  230 ,  280 ,  290 . Likewise, the microfluidic device  250  is another variant of the microfluidic device  100 , and may also have the same or a different DEP configuration as the above-described microfluidic device  100 ,  200 ,  230 ,  280 ,  290 , as well as any of the other microfluidic system components described herein. 
     The microfluidic device  250  of  FIGS. 2D-2F  comprises a support structure (not visible in  FIGS. 2D-2F , but can be the same or generally similar to the support structure  104  of device  100  depicted in  FIG. 1A ), a microfluidic circuit structure  256 , and a cover (not visible in  FIGS. 2D-2F , but can be the same or generally similar to the cover  122  of device  100  depicted in  FIG. 1A ). The microfluidic circuit structure  256  includes a frame  252  and microfluidic circuit material  260 , which can be the same as or generally similar to the frame  114  and microfluidic circuit material  116  of device  100  shown in  FIG. 1A . As shown in  FIG. 2D , the microfluidic circuit  262  defined by the microfluidic circuit material  260  can comprise multiple channels  264  (two are shown but there can be more) to which multiple sequestration pens  266  are fluidically connected. 
     Each sequestration pen  266  can comprise an isolation structure  272 , an isolation region  270  within the isolation structure  272 , and a connection region  268 . From a proximal opening  274  at the microfluidic channel  264  to a distal opening  276  at the isolation structure  272 , the connection region  268  fluidically connects the microfluidic channel  264  to the isolation region  270 . Generally, in accordance with the above discussion of  FIGS. 2B and 2C , a flow  278  of a first fluidic medium  254  in a channel  264  can create secondary flows  282  of the first medium  254  from the microfluidic channel  264  into and/or out of the respective connection regions  268  of the sequestration pens  266 . 
     As illustrated in  FIG. 2E , the connection region  268  of each sequestration pen  266  generally includes the area extending between the proximal opening  274  to a channel  264  and the distal opening  276  to an isolation structure  272 . The length L con  of the connection region  268  can be greater than the maximum penetration depth D p  of secondary flow  282 , in which case the secondary flow  282  will extend into the connection region  268  without being redirected toward the isolation region  270  (as shown in  FIG. 2D ). Alternatively, at illustrated in  FIG. 2F , the connection region  268  can have a length L con  that is less than the maximum penetration depth D p , in which case the secondary flow  282  will extend through the connection region  268  and be redirected toward the isolation region  270 . In this latter situation, the sum of lengths L c1  and L c2  of connection region  268  is greater than the maximum penetration depth D p , so that secondary flow  282  will not extend into isolation region  270 . Whether length L con  of connection region  268  is greater than the penetration depth D p , or the sum of lengths L 1  and L 2  of connection region  268  is greater than the penetration depth D p , a flow  278  of a first medium  254  in channel  264  that does not exceed a maximum velocity V max  will produce a secondary flow having a penetration depth D p , and micro-objects (not shown but can be the same or generally similar to the micro-objects  246  shown in  FIG. 2C ) in the isolation region  270  of a sequestration pen  266  will not be drawn out of the isolation region  270  by a flow  278  of first medium  254  in channel  264 . Nor will the flow  278  in channel  264  draw miscellaneous materials (not shown) from channel  264  into the isolation region  270  of a sequestration pen  266 . As such, diffusion is the only mechanism by which components in a first medium  254  in the microfluidic channel  264  can move from the microfluidic channel  264  into a second medium  258  in an isolation region  270  of a sequestration pen  266 . Likewise, diffusion is the only mechanism by which components in a second medium  258  in an isolation region  270  of a sequestration pen  266  can move from the isolation region  270  to a first medium  254  in the microfluidic channel  264 . The first medium  254  can be the same medium as the second medium  258 , or the first medium  254  can be a different medium than the second medium  258 . Alternatively, the first medium  254  and the second medium  258  can start out being the same, then become different, e.g., through conditioning of the second medium by one or more cells in the isolation region  270 , or by changing the medium flowing through the microfluidic channel  264 . 
     As illustrated in  FIG. 2E , the width W ch  of the microfluidic channels  264  (i.e., taken transverse to the direction of a fluid medium flow through the microfluidic channel indicated by arrows  278  in  FIG. 2D ) in the microfluidic channel  264  can be substantially perpendicular to a width W con1  of the proximal opening  274  and thus substantially parallel to a width W con2  of the distal opening  276 . The width W con2  of the proximal opening  274  and the width W con2  of the distal opening  276 , however, need not be substantially perpendicular to each other. For example, an angle between an axis (not shown) on which the width W con1  of the proximal opening  274  is oriented and another axis on which the width W con2  of the distal opening  276  is oriented can be other than perpendicular and thus other than 90°. Examples of alternatively oriented angles include angles of: about 30° to about 90°, about 45° to about 90°, about 60° to about 90°, or the like. 
     In various embodiments of sequestration pens (e.g.  124 ,  126 ,  128 ,  130 ,  224 ,  226 ,  228 , or  266 ), the isolation region (e.g.  240  or  270 ) is configured to contain a plurality of micro-objects. In other embodiments, the isolation region can be configured to contain only one, two, three, four, five, or a similar relatively small number of micro-objects. Accordingly, the volume of an isolation region can be, for example, at least 1×10 6 , 2×10 6 , 4×10 6 , 6×10 6  cubic microns, or more. 
     In various embodiments of sequestration pens, the width W ch  of the microfluidic channel (e.g., 122) at a proximal opening (e.g.  234 ) can be about 50-1000 microns, 50-500 microns, 50-400 microns, 50-300 microns, 50-250 microns, 50-200 microns, 50-150 microns, 50-100 microns, 70-500 microns, 70-400 microns, 70-300 microns, 70-250 microns, 70-200 microns, 70-150 microns, 90-400 microns, 90-300 microns, 90-250 microns, 90-200 microns, 90-150 microns, 100-300 microns, 100-250 microns, 100-200 microns, 100-150 microns, or 100-120 microns. In some other embodiments, the width W ch  of the microfluidic channel (e.g., 122) at a proximal opening (e.g.  234 ) can be about 200-800 microns, 200-700 microns, or 200-600 microns. The foregoing are examples only, and the width W ch  of the microfluidic channel  122  can be any width within any of the endpoints listed above. Moreover, the W ch  of the microfluidic channel  122  can be selected to be in any of these widths in regions of the microfluidic channel other than at a proximal opening of a sequestration pen. 
     In some embodiments, a sequestration pen has a height of about 30 to about 200 microns, or about 50 to about 150 microns. In some embodiments, the sequestration pen has a cross-sectional area of about 1×10 4 -3×10 6  square microns, 2×10 4 -2×10 6  square microns, 4×10 4 -1×10 6  square microns, 2×10 4 -5×10 5  square microns, 2×10 4 -1×10 5  square microns or about 2×10 5 -2×10 6  square microns. 
     In various embodiments of sequestration pens, the height Ho of the microfluidic channel (e.g.,  122 ) at a proximal opening (e.g.,  234 ) can be a height within any of the following heights: 20-100 microns, 20-90 microns, 20-80 microns, 20-70 microns, 20-60 microns, 20-50 microns, 30-100 microns, 30-90 microns, 30-80 microns, 30-70 microns, 30-60 microns, 30-50 microns, 40-100 microns, 40-90 microns, 40-80 microns, 40-70 microns, 40-60 microns, or 40-50 microns. The foregoing are examples only, and the height Ho of the microfluidic channel (e.g.,  122 ) can be a height within any of the endpoints listed above. The height H ch  of the microfluidic channel  122  can be selected to be in any of these heights in regions of the microfluidic channel other than at a proximal opening of a sequestration pen. 
     In various embodiments of sequestration pens a cross-sectional area of the microfluidic channel e.g.,  122 ) at a proximal opening (e.g.,  234 ) can be about 500-50,000 square microns, 500-40,000 square microns, 500-30,000 square microns, 500-25,000 square microns, 500-20,000 square microns, 500-15,000 square microns, 500-10,000 square microns, 500-7,500 square microns, 500-5,000 square microns, 1,000-25,000 square microns, 1,000-20,000 square microns, 1,000-15,000 square microns, 1,000-10,000 square microns, 1,000-7,500 square microns, 1,000-5,000 square microns, 2,000-20,000 square microns, 2,000-15,000 square microns, 2,000-10,000 square microns, 2,000-7,500 square microns, 2,000-6,000 square microns, 3,000-20,000 square microns, 3,000-15,000 square microns, 3,000-10,000 square microns, 3,000-7,500 square microns, or 3,000 to 6,000 square microns. The foregoing are examples only, and the cross-sectional area of the microfluidic channel (e.g.,  122 ) at a proximal opening (e.g.,  234 ) can be any area within any of the endpoints listed above. 
     In various embodiments of sequestration pens, the length L con  of the connection region (e.g.,  236 ) can be about 1-600 microns, 5-550 microns, 10-500 microns, 15-400 microns, 20-300 microns, 20-500 microns, 40-400 microns, 60-300 microns, 80-200 microns, or about 100-150 microns. The foregoing are examples only, and length L con  of a connection region (e.g.,  236 ) can be in any length within any of the endpoints listed above. 
     In various embodiments of sequestration pens the width W con  of a connection region (e.g.,  236 ) at a proximal opening (e.g.,  234 ) can be about 20-500 microns, 20-400 microns, 20-300 microns, 20-200 microns, 20-150 microns, 20-100 microns, 20-80 microns, 20-60 microns, 30-400 microns, 30-300 microns, 30-200 microns, 30-150 microns, 30-100 microns, 30-80 microns, 30-60 microns, 40-300 microns, 40-200 microns, 40-150 microns, 40-100 microns, 40-80 microns, 40-60 microns, 50-250 microns, 50-200 microns, 50-150 microns, 50-100 microns, 50-80 microns, 60-200 microns, 60-150 microns, 60-100 microns, 60-80 microns, 70-150 microns, 70-100 microns, or 80-100 microns. The foregoing are examples only, and the width W con  of a connection region (e.g.,  236 ) at a proximal opening (e.g.,  234 ) can be different than the foregoing examples (e.g., any value within any of the endpoints listed above). 
     In various embodiments of sequestration pens, the width W con  of a connection region (e.g.,  236 ) at a proximal opening (e.g.,  234 ) can be at least as large as the largest dimension of a micro-object (e.g., biological cell which may be a T cell, or B cell) that the sequestration pen is intended for. The foregoing are examples only, and the width W con  of a connection region (e.g.,  236 ) at a proximal opening (e.g.,  234 ) can be different than the foregoing examples (e.g., a width within any of the endpoints listed above). 
     In various embodiments of sequestration pens, the width W con  of a proximal opening of a connection region may be at least as large as the largest dimension of a micro-object (e.g., a biological micro-object such as a cell) that the sequestration pen is intended for. For example, the width W p r may be about 50 microns, about 60 microns, about 100 microns, about 200 microns, about 300 microns or may be about 50-300 microns, about 50-200 microns, about 50-100 microns, about 75-150 microns, about 75-100 microns, or about 200-300 microns. 
     In various embodiments of sequestration pens, a ratio of the length L con  of a connection region (e.g.,  236 ) to a width W con  of the connection region (e.g.,  236 ) at the proximal opening  234  can be greater than or equal to any of the following ratios: 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, or more. The foregoing are examples only, and the ratio of the length L con  of a connection region  236  to a width W con  of the connection region  236  at the proximal opening  234  can be different than the foregoing examples. 
     In various embodiments of microfluidic devices  100 ,  200 ,  23 ,  250 ,  280 ,  290 , V max  can be set around 0.2, 0.5, 0.7, 1.0, 1.3, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.7, 7.0, 7.5, 8.0, 8.5, 9.0, 10, 11, 12, 13, 14, or 15 microliters/sec. 
     In various embodiments of microfluidic devices having sequestration pens, the volume of an isolation region (e.g.,  240 ) of a sequestration pen can be, for example, at least 5×10 5 , 8×10 5 , 1×10 6 , 2×10 6 , 4×10 6 , 6×10 6 , 8×10 6 , 1×10 7 , 5×10 7 , 1×10 8 , 5×10 8 , or 8×10 8  cubic microns, or more. In various embodiments of microfluidic devices having sequestration pens, the volume of a sequestration pen may be about 5×10 5 , 6×10 5 , 8×10 5 , 1×10 6 , 2×10 6 , 4×10 6 , 8×10 6 , 1×10 7 , 3×10 7 , 5×10 7 , or about 8×10 7  cubic microns, or more. In some other embodiments, the volume of a sequestration pen may be about 1 nanoliter to about 50 nanoliters, 2 nanoliters to about 25 nanoliters, 2 nanoliters to about 20 nanoliters, about 2 nanoliters to about 15 nanoliters, or about 2 nanoliters to about 10 nanoliters. 
     In various embodiment, the microfluidic device has sequestration pens configured as in any of the embodiments discussed herein where the microfluidic device has about 5 to about 10 sequestration pens, about 10 to about 50 sequestration pens, about 100 to about 500 sequestration pens; about 200 to about 1000 sequestration pens, about 500 to about 1500 sequestration pens, about 1000 to about 2000 sequestration pens, about 1000 to about 3500 sequestration pens, about 3000 to about 7000 sequestration pens, about 5000 to about 10,000 sequestration pens, about 9,000 to about 15,000 sequestration pens, or about 12,000 to about 20,000 sequestration pens. The sequestration pens need not all be the same size and may include a variety of configurations (e.g., different widths, different features within the sequestration pen). 
       FIG. 2G  illustrates a microfluidic device  280  according to one embodiment. The microfluidic device  280  illustrated in  FIG. 2G  is a stylized diagram of a microfluidic device  100 . In practice the microfluidic device  280  and its constituent circuit elements (e.g. channels  122  and sequestration pens  128 ) would have the dimensions discussed herein. The microfluidic circuit  120  illustrated in  FIG. 2G  has two ports  107 , four distinct channels  122  and four distinct flow paths  106 . The microfluidic device  280  further comprises a plurality of sequestration pens opening off of each channel  122 . In the microfluidic device illustrated in  FIG. 2G , the sequestration pens have a geometry similar to the pens illustrated in  FIG. 2C  and thus, have both connection regions and isolation regions. Accordingly, the microfluidic circuit  120  includes both swept regions (e.g. channels  122  and portions of the connection regions  236  within the maximum penetration depth D p  of the secondary flow  244 ) and non-swept regions (e.g. isolation regions  240  and portions of the connection regions  236  not within the maximum penetration depth D p  of the secondary flow  244 ). 
       FIGS. 3A through 3B  shows various embodiments of system  150  which can be used to operate and observe microfluidic devices (e.g.  100 ,  200 ,  230 ,  250 ,  280 ,  290 ) according to the present disclosure. As illustrated in  FIG. 3A , the system  150  can include a structure (“nest”)  300  configured to hold a microfluidic device  100  (not shown), or any other microfluidic device described herein. The nest  300  can include a socket  302  capable of interfacing with the microfluidic device  320  (e.g., an optically-actuated electrokinetic device  100 ) and providing electrical connections from power source  192  to microfluidic device  320 . The nest  300  can further include an integrated electrical signal generation subsystem  304 . The electrical signal generation subsystem  304  can be configured to supply a biasing voltage to socket  302  such that the biasing voltage is applied across a pair of electrodes in the microfluidic device  320  when it is being held by socket  302 . Thus, the electrical signal generation subsystem  304  can be part of power source  192 . The ability to apply a biasing voltage to microfluidic device  320  does not mean that a biasing voltage will be applied at all times when the microfluidic device  320  is held by the socket  302 . Rather, in most cases, the biasing voltage will be applied intermittently, e.g., only as needed to facilitate the generation of electrokinetic forces, such as dielectrophoresis or electro-wetting, in the microfluidic device  320 . 
     As illustrated in  FIG. 3A , the nest  300  can include a printed circuit board assembly (PCBA)  322 . The electrical signal generation subsystem  304  can be mounted on and electrically integrated into the PCBA  322 . The exemplary support includes socket  302  mounted on PCBA  322 , as well. 
     Typically, the electrical signal generation subsystem  304  will include a waveform generator (not shown). The electrical signal generation subsystem  304  can further include an oscilloscope (not shown) and/or a waveform amplification circuit (not shown) configured to amplify a waveform received from the waveform generator. The oscilloscope, if present, can be configured to measure the waveform supplied to the microfluidic device  320  held by the socket  302 . In certain embodiments, the oscilloscope measures the waveform at a location proximal to the microfluidic device  320  (and distal to the waveform generator), thus ensuring greater accuracy in measuring the waveform actually applied to the device. Data obtained from the oscilloscope measurement can be, for example, provided as feedback to the waveform generator, and the waveform generator can be configured to adjust its output based on such feedback. An example of a suitable combined waveform generator and oscilloscope is the Red Pitaya™. 
     In certain embodiments, the nest  300  further comprises a controller  308 , such as a microprocessor used to sense and/or control the electrical signal generation subsystem  304 . Examples of suitable microprocessors include the Arduino™ microprocessors, such as the Arduino Nano™. The controller  308  may be used to perform functions and analysis or may communicate with an external master controller  154  (shown in  FIG. 1A ) to perform functions and analysis. In the embodiment illustrated in  FIG. 3A  the controller  308  communicates with a master controller  154  through an interface  310  (e.g., a plug or connector). 
     In some embodiments, the nest  300  can comprise an electrical signal generation subsystem  304  comprising a Red Pitaya™ waveform generator/oscilloscope unit (“Red Pitaya unit”) and a waveform amplification circuit that amplifies the waveform generated by the Red Pitaya unit and passes the amplified voltage to the microfluidic device  100 . In some embodiments, the Red Pitaya unit is configured to measure the amplified voltage at the microfluidic device  320  and then adjust its own output voltage as needed such that the measured voltage at the microfluidic device  320  is the desired value. In some embodiments, the waveform amplification circuit can have a +6.5V to −6.5V power supply generated by a pair of DC-DC converters mounted on the PCBA  322 , resulting in a signal of up to 13 Vpp at the microfluidic device  100 . 
     As illustrated in  FIG. 3A , the support structure  300  (e.g., nest) can further include a thermal control subsystem  306 . The thermal control subsystem  306  can be configured to regulate the temperature of microfluidic device  320  held by the support structure  300 . For example, the thermal control subsystem  306  can include a Peltier thermoelectric device (not shown) and a cooling unit (not shown). The Peltier thermoelectric device can have a first surface configured to interface with at least one surface of the microfluidic device  320 . The cooling unit can be, for example, a cooling block (not shown), such as a liquid-cooled aluminum block. A second surface of the Peltier thermoelectric device (e.g., a surface opposite the first surface) can be configured to interface with a surface of such a cooling block. The cooling block can be connected to a fluidic path  314  configured to circulate cooled fluid through the cooling block. In the embodiment illustrated in  FIG. 3A , the support structure  300  comprises an inlet  316  and an outlet  318  to receive cooled fluid from an external reservoir (not shown), introduce the cooled fluid into the fluidic path  314  and through the cooling block, and then return the cooled fluid to the external reservoir. In some embodiments, the Peltier thermoelectric device, the cooling unit, and/or the fluidic path  314  can be mounted on a casing  312  of the support structure  300 . In some embodiments, the thermal control subsystem  306  is configured to regulate the temperature of the Peltier thermoelectric device so as to achieve a target temperature for the microfluidic device  320 . Temperature regulation of the Peltier thermoelectric device can be achieved, for example, by a thermoelectric power supply, such as a Pololu™ thermoelectric power supply (Pololu Robotics and Electronics Corp.). The thermal control subsystem  306  can include a feedback circuit, such as a temperature value provided by an analog circuit. Alternatively, the feedback circuit can be provided by a digital circuit. 
     In some embodiments, the nest  300  can include a thermal control subsystem  306  with a feedback circuit that is an analog voltage divider circuit (not shown) which includes a resistor (e.g., with resistance  1  kOhm+/−0.1%, temperature coefficient +/−0.02 ppm/C0) and a NTC thermistor (e.g., with nominal resistance  1  kOhm+/−0.01%). In some instances, the thermal control subsystem  306  measures the voltage from the feedback circuit and then uses the calculated temperature value as input to an on-board PID control loop algorithm. Output from the PID control loop algorithm can drive, for example, both a directional and a pulse-width-modulated signal pin on a Pololu™ motor drive (not shown) to actuate the thermoelectric power supply, thereby controlling the Peltier thermoelectric device. 
     The nest  300  can include a serial port  324  which allows the microprocessor of the controller  308  to communicate with an external master controller  154  via the interface  310  (not shown). In addition, the microprocessor of the controller  308  can communicate (e.g., via a Plink tool (not shown)) with the electrical signal generation subsystem  304  and thermal control subsystem  306 . Thus, via the combination of the controller  308 , the interface  310 , and the serial port  324 , the electrical signal generation subsystem  304  and the thermal control subsystem  306  can communicate with the external master controller  154 . In this manner, the master controller  154  can, among other things, assist the electrical signal generation subsystem  304  by performing scaling calculations for output voltage adjustments. A Graphical User Interface (GUI) (not shown) provided via a display device  170  coupled to the external master controller  154 , can be configured to plot temperature and waveform data obtained from the thermal control subsystem  306  and the electrical signal generation subsystem  304 , respectively. Alternatively, or in addition, the GUI can allow for updates to the controller  308 , the thermal control subsystem  306 , and the electrical signal generation subsystem  304 . 
     As discussed above, system  150  can include an imaging device  194 . In some embodiments, the imaging device  194  comprises a light modulating subsystem  330  (See  FIG. 3B ). The light modulating subsystem  330  can include a digital mirror device (DMD) or a microshutter array system (MSA), either of which can be configured to receive light from a light source  332  and transmits a subset of the received light into an optical train of microscope  350 . Alternatively, the light modulating subsystem  330  can include a device that produces its own light (and thus dispenses with the need for a light source  332 ), such as an organic light emitting diode display (OLED), a liquid crystal on silicon (LCOS) device, a ferroelectric liquid crystal on silicon device (FLCOS), or a transmissive liquid crystal display (LCD). The light modulating subsystem  330  can be, for example, a projector. Thus, the light modulating subsystem  330  can be capable of emitting both structured and unstructured light. In certain embodiments, imaging module  164  and/or motive module  162  of system  150  can control the light modulating subsystem  330 . 
     In certain embodiments, the imaging device  194  further comprises a microscope  350 . In such embodiments, the nest  300  and light modulating subsystem  330  can be individually configured to be mounted on the microscope  350 . The microscope  350  can be, for example, a standard research-grade light microscope or fluorescence microscope. Thus, the nest  300  can be configured to be mounted on the stage  344  of the microscope  350  and/or the light modulating subsystem  330  can be configured to mount on a port of microscope  350 . In other embodiments, the nest  300  and the light modulating subsystem  330  described herein can be integral components of microscope  350 . 
     In certain embodiments, the microscope  350  can further include one or more detectors  348 . In some embodiments, the detector  348  is controlled by the imaging module  164 . The detector  348  can include an eye piece, a charge-coupled device (CCD), a camera (e.g., a digital camera), or any combination thereof. If at least two detectors  348  are present, one detector can be, for example, a fast-frame-rate camera while the other detector can be a high sensitivity camera. Furthermore, the microscope  350  can include an optical train configured to receive reflected and/or emitted light from the microfluidic device  320  and focus at least a portion of the reflected and/or emitted light on the one or more detectors  348 . The optical train of the microscope can also include different tube lenses (not shown) for the different detectors, such that the final magnification on each detector can be different. 
     In certain embodiments, imaging device  194  is configured to use at least two light sources. For example, a first light source  332  can be used to produce structured light (e.g., via the light modulating subsystem  330 ) and a second light source  334  can be used to provide unstructured light. The first light source  332  can produce structured light for optically-actuated electrokinesis and/or fluorescent excitation, and the second light source  334  can be used to provide bright field illumination. In these embodiments, the motive module  164  can be used to control the first light source  332  and the imaging module  164  can be used to control the second light source  334 . The optical train of the microscope  350  can be configured to (1) receive structured light from the light modulating subsystem  330  and focus the structured light on at least a first region in a microfluidic device, such as an optically-actuated electrokinetic device, when the device is being held by the nest  300 , and (2) receive reflected and/or emitted light from the microfluidic device and focus at least a portion of such reflected and/or emitted light onto detector  348 . The optical train can be further configured to receive unstructured light from a second light source and focus the unstructured light on at least a second region of the microfluidic device, when the device is held by the nest  300 . In certain embodiments, the first and second regions of the microfluidic device can be overlapping regions. For example, the first region can be a subset of the second region. In other embodiments, the second light source  334  may additionally or alternatively include a laser, which may have any suitable wavelength of light. The representation of the optical system shown in  FIG. 3B  is a schematic representation only, and the optical system may include additional filters, notch filters, lenses and the like. When the second light source  334  includes one or more light source(s) for brighffield and/or fluorescent excitation, as well as laser illumination the physical arrangement of the light source(s) may vary from that shown in  FIG. 3B , and the laser illumination may be introduced at any suitable physical location within the optical system. The schematic locations of light source  334  and light source  332 /light modulating subsystem  330  may be interchanged as well. 
     In  FIG. 3B , the first light source  332  is shown supplying light to a light modulating subsystem  330 , which provides structured light to the optical train of the microscope  350  of system  355  (not shown). The second light source  334  is shown providing unstructured light to the optical train via a beam splitter  336 . Structured light from the light modulating subsystem  330  and unstructured light from the second light source  334  travel from the beam splitter  336  through the optical train together to reach a second beam splitter (or dichroic filter  338 , depending on the light provided by the light modulating subsystem  330 ), where the light gets reflected down through the objective  336  to the sample plane  342 . Reflected and/or emitted light from the sample plane  342  then travels back up through the objective  340 , through the beam splitter and/or dichroic filter  338 , and to a dichroic filter  346 . Only a fraction of the light reaching dichroic filter  346  passes through and reaches the detector  348 . 
     In some embodiments, the second light source  334  emits blue light. With an appropriate dichroic filter  346 , blue light reflected from the sample plane  342  is able to pass through dichroic filter  346  and reach the detector  348 . In contrast, structured light coming from the light modulating subsystem  330  gets reflected from the sample plane  342 , but does not pass through the dichroic filter  346 . In this example, the dichroic filter  346  is filtering out visible light having a wavelength longer than 495 nm. Such filtering out of the light from the light modulating subsystem  330  would only be complete (as shown) if the light emitted from the light modulating subsystem did not include any wavelengths shorter than 495 nm. In practice, if the light coming from the light modulating subsystem  330  includes wavelengths shorter than 495 nm (e.g., blue wavelengths), then some of the light from the light modulating subsystem would pass through filter  346  to reach the detector  348 . In such an embodiment, the filter  346  acts to change the balance between the amount of light that reaches the detector  348  from the first light source  332  and the second light source  334 . This can be beneficial if the first light source  332  is significantly stronger than the second light source  334 . In other embodiments, the second light source  334  can emit red light, and the dichroic filter  346  can filter out visible light other than red light (e.g., visible light having a wavelength shorter than 650 nm). 
     Coating solutions and coating agents. Without intending to be limited by theory, maintenance of a biological micro-object (e.g., a biological cell) within a microfluidic device (e.g., a DEP-configured and/or EW-configured microfluidic device) may be facilitated (i.e., the biological micro-object exhibits increased viability, greater expansion and/or greater portability within the microfluidic device) when at least one or more inner surfaces of the microfluidic device have been conditioned or coated so as to present a layer of organic and/or hydrophilic molecules that provides the primary interface between the microfluidic device and biological micro-object(s) maintained therein. In some embodiments, one or more of the inner surfaces of the microfluidic device (e.g. the inner surface of the electrode activation substrate of a DEP-configured microfluidic device, the cover of the microfluidic device, and/or the surfaces of the circuit material) may be treated with or modified by a coating solution and/or coating agent to generate the desired layer of organic and/or hydrophilic molecules. 
     The coating may be applied before or after introduction of biological micro-object(s), or may be introduced concurrently with the biological micro-object(s). In some embodiments, the biological micro-object(s) may be imported into the microfluidic device in a fluidic medium that includes one or more coating agents. In other embodiments, the inner surface(s) of the microfluidic device (e.g., a DEP-configured microfluidic device) are treated or “primed” with a coating solution comprising a coating agent prior to introduction of the biological micro-object(s) into the microfluidic device. 
     In some embodiments, at least one surface of the microfluidic device includes a coating material that provides a layer of organic and/or hydrophilic molecules suitable for maintenance and/or expansion of biological micro-object(s) (e.g. provides a conditioned surface as described below). In some embodiments, substantially all the inner surfaces of the microfluidic device include the coating material. The coated inner surface(s) may include the surface of a flow region (e.g., channel), chamber, or sequestration pen, or a combination thereof. In some embodiments, each of a plurality of sequestration pens has at least one inner surface coated with coating materials. In other embodiments, each of a plurality of flow regions or channels has at least one inner surface coated with coating materials. In some embodiments, at least one inner surface of each of a plurality of sequestration pens and each of a plurality of channels is coated with coating materials. 
     Coating Agent/Solution. 
     Any convenient coating agent/coating solution can be used, including but not limited to: serum or serum factors, bovine serum albumin (BSA), polymers, detergents, enzymes, and any combination thereof. 
     Polymer-Based Coating Materials. 
     The at least one inner surface may include a coating material that comprises a polymer. The polymer may be covalently or non-covalently bound (or may be non-specifically adhered) to the at least one surface. The polymer may have a variety of structural motifs, such as found in block polymers (and copolymers), star polymers (star copolymers), and graft or comb polymers (graft copolymers), all of which may be suitable for the methods disclosed herein. 
     The polymer may include a polymer including alkylene ether moieties. A wide variety of alkylene ether containing polymers may be suitable for use in the microfluidic devices described herein. One non-limiting exemplary class of alkylene ether containing polymers are amphiphilic nonionic block copolymers which include blocks of polyethylene oxide (PEO) and polypropylene oxide (PPO) subunits in differing ratios and locations within the polymer chain. Pluronic® polymers (BASF) are block copolymers of this type and are known in the art to be suitable for use when in contact with living cells. The polymers may range in average molecular mass M w  from about 2000 Da to about 20 KDa. In some embodiments, the PEO-PPO block copolymer can have a hydrophilic-lipophilic balance (HLB) greater than about 10 (e.g. 12-18). Specific Pluronic® polymers useful for yielding a coated surface include Pluronic® L44, L64, P85, and F127 (including F127NF). Another class of alkylene ether containing polymers is polyethylene glycol (PEG M w &lt;100,000 Da) or alternatively polyethylene oxide (PEO, M w &gt;100,000). In some embodiments, a PEG may have an M w  of about 88 Da, 100 Da, 132 Da, 176 Da, 200 Da, 220 Da, 264 Da, 308 Da, 352 Da, 396 Da, 440 Da, 500 Da, 600 Da, 700 Da, 800 Da, 900 Da, 1000 Da, 1500 Da, 2000 Da, 5000 Da, 10,000 Da or 20,000 Da, or may have a M w  that falls within a range defined by any two of the foregoing values. 
     In other embodiments, the coating material may include a polymer containing carboxylic acid moieties. The carboxylic acid subunit may be an alkyl, alkenyl or aromatic moiety containing subunit. One non-limiting example is polylactic acid (PLA). In other embodiments, the coating material may include a polymer containing phosphate moieties, either at a terminus of the polymer backbone or pendant from the backbone of the polymer. In yet other embodiments, the coating material may include a polymer containing sulfonic acid moieties. The sulfonic acid subunit may be an alkyl, alkenyl or aromatic moiety containing subunit. One non-limiting example is polystyrene sulfonic acid (PSSA) or polyanethole sulfonic acid. In further embodiments, the coating material may include a polymer including amine moieties. The polyamino polymer may include a natural polyamine polymer or a synthetic polyamine polymer. Examples of natural polyamines include spermine, spermidine, and putrescine. 
     In other embodiments, the coating material may include a polymer containing saccharide moieties. In a non-limiting example, polysaccharides such as xanthan gum or dextran may be suitable to form a material which may reduce or prevent cell sticking in the microfluidic device. For example, a dextran polymer having a size about 3 kDa may be used to provide a coating material for a surface within a microfluidic device. 
     In other embodiments, the coating material may include a polymer containing nucleotide moieties, i.e. a nucleic acid, which may have ribonucleotide moieties or deoxyribonucleotide moieties, providing a polyelectrolyte surface. The nucleic acid may contain only natural nucleotide moieties or may contain unnatural nucleotide moieties which comprise nucleobase, ribose or phosphate moiety analogs such as 7-deazaadenine, pentose, methyl phosphonate or phosphorothioate moieties without limitation. 
     In yet other embodiments, the coating material may include a polymer containing amino acid moieties. The polymer containing amino acid moieties may include a natural amino acid containing polymer or an unnatural amino acid containing polymer, either of which may include a peptide, a polypeptide or a protein. In one non-limiting example, the protein may be bovine serum albumin (BSA) and/or serum (or a combination of multiple different sera) comprising albumin and/or one or more other similar proteins as coating agents. The serum can be from any convenient source, including but not limited to fetal calf serum, sheep serum, goat serum, horse serum, and the like. In certain embodiments, BSA in a coating solution is present in a concentration from about 1 mg/mL to about 100 mg/mL, including 5 mg/mL, 10 mg/mL, 20 mg/mL, 30 mg/mL, 40 mg/mL, 50 mg/mL, 60 mg/mL, 70 mg/mL, 80 mg/mL, 90 mg/mL, or more or anywhere in between. In certain embodiments, serum in a coating solution may be present in a concentration of about 20% (v/v) to about 50% v/v, including 25%, 30%, 35%, 40%, 45%, or more or anywhere in between. In some embodiments, BSA may be present as a coating agent in a coating solution at 5 mg/mL, whereas in other embodiments, BSA may be present as a coating agent in a coating solution at 70 mg/mL. In certain embodiments, serum is present as a coating agent in a coating solution at 30%. In some embodiments, an extracellular matrix (ECM) protein may be provided within the coating material for optimized cell adhesion to foster cell growth. A cell matrix protein, which may be included in a coating material, can include, but is not limited to, a collagen, an elastin, an RGD-containing peptide (e.g. a fibronectin), or a laminin. In yet other embodiments, growth factors, cytokines, hormones or other cell signaling species may be provided within the coating material of the microfluidic device. 
     In some embodiments, the coating material may include a polymer containing more than one of alkylene oxide moieties, carboxylic acid moieties, sulfonic acid moieties, phosphate moieties, saccharide moieties, nucleotide moieties, or amino acid moieties. In other embodiments, the polymer conditioned surface may include a mixture of more than one polymer each having alkylene oxide moieties, carboxylic acid moieties, sulfonic acid moieties, phosphate moieties, saccharide moieties, nucleotide moieties, and/or amino acid moieties, which may be independently or simultaneously incorporated into the coating material. 
     In addition, in embodiments in which a covalently modified surface is used in conjunction with coating agents, the anions, cations, and/or zwitterions of the covalently modified surface can form ionic bonds with the charged portions of non-covalent coating agents (e.g. proteins in solution) that are present in a fluidic medium (e.g. a coating solution) in the enclosure. 
     Further details of appropriate coating treatments and modifications may be found at U.S. application Ser. No. 15/135,707, filed on Apr. 22, 2016, and is incorporated by reference in its entirety. 
     Additional System Components for Maintenance of Viability of Cells within the Sequestration Pens of the Microfluidic Device. 
     In order to promote growth and/or expansion of cell populations, environmental conditions conducive to maintaining functional cells may be provided by additional components of the system. For example, such additional components can provide nutrients, cell growth signaling species, pH modulation, gas exchange, temperature control, and removal of waste products from cells. 
     EXAMPLES 
     General Materials and Methods. 
     System and Microfluidic Device: 
     An OptoSelect chip, a microfluidic (or nanofluidic) device manufactured by Berkeley Lights, Inc. and controlled by an optical instrument which was also manufactured by Berkeley Lights, Inc. The instrument included: a mounting stage for the chip coupled to a temperature controller; a pump and fluid medium conditioning component; and an optical train including a camera and a structured light source suitable for activating phototransistors within the chip. The OptoSelect™ chip included a substrate configured with OptoElectroPositioning (OEP™) technology, which provides a phototransistor-activated OET force. The chip also included a plurality of microfluidic channels, each having a plurality of NanoPen™ chambers (or sequestration pens) fluidically connected thereto. The volume of each sequestration pen was around 1×10 6  cubic microns. 
     Priming Solution: 
     Complete growth medium containing 0.1% Pluronic® F127 ((Life Technologies® Cat # P6866). 
     Preparation for culturing: The microfluidic device having a modified surface was loaded onto the system and purged with 100% carbon dioxide at 15 psi for 5 min. Immediately following the carbon dioxide purge, the priming solution was perfused through the microfluidic device at 5 microliters/sec for 8 min. Culture medium was then flowed through the microfluidic device at 5 microliters/sec for 5 min. 
     Priming Regime. 
     250 microliters of 100% carbon dioxide was flowed in at a rate of 12 microliters/sec. This was followed by 250 microliters of PBS containing 0.1% Pluronic® F27 (Life Technologies® Cat # P6866), flowed in at 12 microliters/sec. The final step of priming included 250 microliters of PBS, flowed in at 12 microliters/sec. Introduction of the culture medium follows. 
     Perfusion regime. 
     The perfusion method was either of the following two methods: 
     1. Perfuse at 0.01 microliters/sec for 2 h; perfuse at 2 microliters/sec for 64 sec; and repeat. 
     2. Perfuse at 0.02 microliters/sec for 100 sec; stop flow 500 sec; perfuse at 2 microliters/sec for 64 sec; and repeat. 
     Example 1. Preparation of a Functionalized Surface of an Unpatterned Silicon Wafer 
     A silicon wafer (780 microns thick, 1 cm by 1 cm) was treated in an oxygen plasma cleaner (Nordson Asymtek) for 5 min, using 100 W power, 240 mTorr pressure and 440 sccm oxygen flow rate. The plasma treated silicon wafer was treated in a vacuum reactor with (11-azidoundecyl) trimethoxy silane (300 microliters) in a foil boat in the bottom of the vacuum reactor in the presence of magnesium sulfate heptahydrate (0.5 g, Acros Cat. #10034-99-8), as a water reactant source in a separate foil boat in the bottom of the vacuum reactor. The chamber was then pumped to 750 mTorr using a vacuum pump and then sealed. The vacuum reactor was placed within an oven heated at 110° C. for 24-48 h. This introduced a modified surface to the wafer, where the modified surface had a structure of Formula I: 
     
       
         
         
             
             
         
       
     
     After cooling to room temperature and introducing argon to the evacuated chamber, the wafer was removed from the reactor. The wafer was rinsed with acetone, isopropanol, and dried under a stream of nitrogen. Confirmation of introduction of the modified surface was made by ellipsometry and contact angle goniometry. 
     Alternatively, the silicon wafer was cut to size to fit within the bottom of a flat bottomed wellplate before introducing the functionalized surface of Formula I upon it, and a plurality of the formatted silicon wafers were functionalized at the same time. 
     Example 2. Preparation of a Planar Unpatterned Silicon Wafer Having a Streptavidin Functionalized Surface 
     The product silicon wafer from Example 1, having a surface of Formula I as described above, was treated with dibenzylcyclooctynyl (DBCO) Streptavidin (SAV), Nanocs, Cat. # SV1-DB-1, where there are 2-7 DBCO for each molecule of SAV) by contacting the silicon wafer with an aqueous solution containing a 2 micromolar solution of the commercially available DBCO-SAV. The reaction was allowed to proceed at room temperature for at least 1 h. The unpatterned silicon wafer having a modified surface of Formula II was then rinsed with 1×PBS. 
     
       
         
         
             
             
         
       
     
     Example 3. Synthesis of DBCO-Labeled Streptavidin (SAV) Compound 1 
     5 mg of lyophilized SAV (ThermoFisher PN # S888) was dissolved into 1 mL of 1×PBS (Gibco) and 1 mL of 2 mM Na 2 CO 3  (Acros) in 1×PBS. 10 mg of neat DBCO-PEG13-NHS (Compound 2, Click Chemistry Tools PN #1015-10) was dissolved into 0.4 mL of dry DMSO. 16 uL of the DBCO-PEG13-NHS solution was added to the SAV solution and mixed at 400 RPM at 25° C. for 4 h on an Eppendorf ThermoMixer. The labeled SAV (Compound 1) was purified from the DBCO-PEG13-NHS by passing the reaction mixture through Zeba size exclusion chromatography spin columns (ThermoFisher PN #89882), and used without further purification. 
     
       
         
         
             
             
         
       
     
     Example 4. Preparation of a Planar Unpatterned Silicon Wafer Having a Streptavidin Functionalized Surface 
     The product silicon wafer from Example 1, having a surface of Formula I as described above, was treated with Compound 1 (DBCO linked Streptavidin (SAV), product of Example 3, having a PEG 13 linker, where there are 2-7 DBCO for each molecule of SAV) by contacting the silicon wafer with an aqueous solution containing 2 micromolar Compound 1. The reaction was allowed to proceed at room temperature for at least 1 h. The unpatterned silicon wafer having a streptavidin covalently functionalized surface including a PEG 13 linker was then rinsed with 1×PBS. 
     Example 5. Comparison of Functionalization of Silicon Wafers with Commercially Available DBCO Linked SAV Compared with Functionalization Using Compound 1 
     Comparison of the SAV modified surfaces was made by ellipsometry and contact angle goniometry after each step of introduction of reactive azide moieties (Example 1); introduction of respective SAV layers; followed by introduction of biotinylated anti-CD28, where the concentrations of reagents and reaction conditions were the same. Sample 2, using the DBCO SAV reagent having a linker including a PEG13 moiety, clearly provided a more robust functionalization of SAV than that of Sample 1, and subsequently, more robust functionalization by biotinylated anti-CD2 binding to the SAV binding sites. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                 Overall 
                 Overall 
                   
                 Thickness of 
               
               
                   
                   
                 Thickness after 
                 Thickness after 
                 Thickness of 
                 anti-CD28 
               
               
                   
                 Thickness of 
                 DBCO SAV 
                 anti-CD 28 
                 SAV layer 
                 layer 
               
               
                   
                 azide layer 
                 coupling 
                 binding 
                 introduced 
                 introduced 
               
               
                 Sample 
                 (Angstroms) 
                 (Angstroms) 
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                 Wafer 1, from 
                 13.31 
                 25.22 
                 28.54 
                 11.91 
                 3.32 
               
               
                 Ex. 2 
               
               
                 Wafer 2, from 
                 13.43 
                 45.08 
                 62.37 
                 31.65 
                 17.29 
               
               
                 Ex. 4 
               
               
                   
               
            
           
         
       
     
     Without being bound by theory, it was shown that a linker having a length of at least 5 PEG repeat units up to about 20 PEG repeat units (alternatively, a linker having a length from about 20 Angstroms to about 100 Angstroms) may provide superior levels of coupling to the reactive moieties on this reactive surface of the silicon wafer. This is further demonstrated by the additional thickness of the layer of anti-CD28 introduced in Sample Wafer 2, as more SAV binding sites were available. 
     Example 6. Preparation of Planar Patterned Surfaces, and Further Elaboration to Provide Antigen Presenting Surfaces within a Plurality of Regions Separated by a Differing Region Having No Activation Functionalization 
     Indium tin oxide (ITO) wafers were fabricated to have a patterned plurality of regions of amorphous silicon upon the ITO. The regions were a.) 1 micron diameter round amorphous silicon regions separated by three microns from each other or b.) 2 micron square amorphous silicon regions separated by 2 microns from each other.  FIGS. 6A and 6B  show SEM images of portions of each type of patterned surface. 
     The patterned wafers were cleaned prior to functionalization by sonication for 10 minutes in acetone, rinsed with deionized water, and dried (Step 1 of  FIG. 6 ). The patterned wafers were then treated in an oxygen plasma cleaner (Nordson Asymtek) for 5 min, using 100 W power, 240 mTorr pressure and 440 sccm oxygen flow rate. 
     A Schematic Representation of the Functionalization Process is Shown in  FIG. 6 . Initial Covalent Modification of the ITO Surface. 
     The indium tin oxide base layer of the wafer was functionalized by reaction with 40 mM undecynyl phosphonic acid (Sikemia Catalog # SIK7110-10) in 50% N-methylpyrrolidine (NMP)/water solution (Step 2 of  FIG. 6 ). The cleaned surface of the wafers was submerged in the solution within a vial and sealed. The vial was maintained in a 50° C. water bath overnight. The next day, the wafers were removed and washed with 50% isopropyl alcohol/water, followed by isopropyl alcohol. 
     A. Biotinylation of the ITO Region of the Patterned Surface. 
     The alkyne functionalized ITO region was further covalently modified by reaction with 1.5 mM biotin linked to an azido reactive moiety (azide-S-S-biotin, Broadpharm Catalog # BP-2877), 0.5 mM sodium ascorbate; and 1 mM Cu(II)SO 4 /THPTA in water (Step 3 of  FIG. 6 ). Care was taken to premix the copper ligand and sodium ascorbate prior to contact with the disulfide containing biotin reagent. The surfaces were allowed to remain in contact with the biotin reagent solution for one hour. The surfaces of the wafers were then washed with water, and dried, in preparation for the next step. 
     B. Covalent Modification of the Surfaces of the Plurality of Amorphous Silicon Regions of the Patterned Wafer. 
     The patterned wafers having biotinylated surface within the ITO region of the wafer was treated in a vacuum reactor with (11-azidoundecyl) trimethoxy silane (Compound 3, 300 microliters) in a foil boat in the bottom of the vacuum reactor in the presence of magnesium sulfate heptahydrate (0.5 g, Acros Cat. #10034-99-8), as a water reactant source in a separate foil boat in the bottom of the vacuum reactor (Step 4 of  FIG. 6 ). The chamber was then pumped to 750 mTorr using a vacuum pump and then sealed. The vacuum reactor was placed within an oven heated at 110° C. overnight. This introduced a modified surface to the plurality of amorphous silicon regions on the wafer, where the modified surface had a structure of Formula I: 
     
       
         
         
             
             
         
       
     
     After cooling to room temperature and introducing argon to the evacuated chamber, the wafer was removed from the reactor. The wafer was rinsed with acetone, isopropanol, and dried under a stream of nitrogen. Metrology showed that the biotinylated ITO region of the patterned wafer did not have substantial amounts of contamination of the functionalizing ligands of Formula I; 10% or less contaminant was found. 
     C. Covalent Modification of the Biotin-Modified ITO Region of the Patterned Wafer to Provide Supportive Moieties. 
     The patterned wafers having a plurality of undecyl azido modified amorphous silicon regions separated by a biotin modified ITO region was reacted with a solution of streptavidin (SAV, 3.84 micromolar) in PBS containing 0.02% sodium azide and allowed to incubate for 30 min (Step 5 of  FIG. 6 ). The wafer was then washed with PBS and dried. 
     The streptavidin modified surface of the ITO region of the patterned wafers is then modified by reaction with a 200 micromolar solution of biotin-RGD (Anaspec Catalog # AS-62347) in PBS containing 0.02% sodium azide, thereby providing adhesive moieties for general improvement in viability of the T lymphocytes when cultured upon these surfaces (Step 6 of  FIG. 6 ). After incubating for 45 min, the wafers are rinsed with PBS and then dried. 
     Further Generalization. 
     The streptavidin modified surface of the ITO region of the patterned wafers may alternatively be modified by reaction with a 200 micromolar solution of biotin-PEG-5K (Jenkem Catalog # M-BIOTIN-5000) to provide hydrophilic moieties within this non-activating region of the patterned surface. Further the streptavidin surface may be modified by a mixture of the adhesive and hydrophilic moieties by reacting the streptavidin surface with a mixture of 200 micromolar stock solutions of the biotinylated moieties, in any ratio, e.g., 1:1: 1:10; 10:1 or any ration therebetween. 
     D. 
     Providing a secondary functionalized surface to the plurality of azido functionalized amorphous silicon regions of the patterned wafers. A solution of DBCO-SAV (Nanocs Catalog # SV1-DB-1, 2 micromolar) in PBS containing 0.02% sodium azide was contacted with the patterned wafer having a plurality of azido-functionalized amorphous silicon regions separated by a region of ITO having supportive moieties (e.g., adhesive motifs such as RGD, or hydrophilic moieties such as PEG-5K) covalently attached thereupon, for an incubation period of 30 min, providing a plurality of amorphous regions having a streptavidin functionalized surface separated by the region of supportively modified ITO surface (Step 7 of  FIG. 6 ). The patterned wafers were maintained in PBS/0.02% sodium azide until final introduction of the antigen activating ligands. 
     E. 
     Functionalization of streptavidin modified surfaces of the amorphous silicon regions of the patterned wafer (Step 8 of  FIG. 6 ). Stepwise functionalization is performed similarly as in Example 12, first exposing the patterned surfaces to biotinylated Monomer MHC (HLA-A*02:01 MART-1 (MBL International Corp., Catalog No. MR01008, ELAGIGILTV) in solution, and incubation for 45 minutes. After rinsing the patterned wafer having a plurality of MHC modified amorphous silicon regions with Wash Buffer, the patterned wafer is then contacted with a solution of biotinylated anti-CD28 (Miltenyi Biotec, Catalog #130-100-144) and incubated for 30-45 minutes to provide a plurality of pMHC/anti-CD28 regions separated by a supportively modified ITO region of the patterned wafer. 
     Example 7. Activation of CD8+ T Lymphocytes Using a Patterned Surface Containing a Plurality of Regions Having pMHC and Anti-CD28 Connected Thereto, Separated by a Region Having Supportive Moieties Connected Thereto Compared to an Unpatterned Surface 
     The product patterned wafer of Example 6 was sized for placement within the bottom of a well of a 48-well plate. Two different patterned surfaces were used, the first having circular regions having a diameter of 1 micron, such as shown in  FIG. 7A  and the second having square regions of 2 microns each side as shown in  FIG. 7B . A planar third surface, unpatterned, having a random distribution of the same level of MHC peptide modification and anti-CD28 was used in a third well of a third 48 well plate. Only one level of anti-CD28 antibody loading to the planar surfaces was used. Naïve T-lymphocytes, obtained as described in Example 12 (below) were disposed within the wells of the well plates and in contact with the patterned or unpatterned wafer. The stimulation protocol and culturing protocol were each performed as in Example 12 for days 1-7. Flow cytometry analysis showed activation of the naïve T lymphocytes. The flow cytometry results as shown in  FIGS. 8A-8D  show that each of the three kinds of surfaces can activate T lymphocytes. Graphical characterization shown in  FIGS. 8A-D  for these three conditions of activation show that phenotypic specificity is obtained.  FIG. 8A  shows the percentage of antigen specific (MART1) T cells found in the product cell populations for each of the 1 micron activating island patterns, 2 micron activating island patterns, and unpatterned wafer surface.  FIG. 8B  shows the total number of MART 1 antigen specific T cells found in each of the resultant cell populations for each surface type.  FIG. 8C  shows the fold expansion of MART 1 antigen specific T cells for each of the surface type.  FIG. 8D  shows the percentage of CD28high expressing antigen specific T cells within the antigen specific T cell population for each surface type. The patterned surfaces demonstrate more reproducible and controllable amounts of expansion, phenotype and actual numbers of cells. The smaller 1 micron regions may more effectively mimic the natural preferred arrangement of presented antigen, MHC molecule and anti-CD 28. See  FIG. 9 . 
     After the first period of stimulation is complete, the resultant T cells are restimulated for Days 7-14, and optionally for Days 14-21 within the same well of the well plate, adding the cytokine additions as above. Alternatively, on Day 7 and/or Day 14, the resultant T lymphocytes may be moved to a new well having a fresh patterned wafer, and the protocol of Example 12 continued. At the end of the desired repetitions of stimulation, a portion of the cells may be stained and examined by flow cytometry to determine the extent of activation. It is expected that the patterned surface wafers stimulate T cell activation as readily as bead-based activation or activation by antigen presenting Dendritic cells. 
     Example 8. Preparation of a Microfluidic Device Having Modified Interior Surfaces of Formula I 
     A microfluidic device (Berkeley Lights, Inc.) as described in the general experimental section above, having a first silicon electrode activation substrate and a second ITO substrate on the opposite wall, and photopatterned silicone microfluidic circuit material separating the two substrates, was treated in an oxygen plasma cleaner (Nordson Asymtek) for 1 min, using 100 W power, 240 mTorr pressure and 440 sccm oxygen flow rate. The plasma treated microfluidic device was treated in a vacuum reactor with 3-azidoundecyl) trimethoxy silane (300 microliters) in a foil boat in the bottom of the vacuum reactor in the presence of magnesium sulfate heptahydrate (0.5 g, Acros), as a water reactant source in a separate foil boat in the bottom of the vacuum reactor. The chamber was then pumped to 750 mTorr using a vacuum pump and then sealed. The vacuum reactor was placed within an oven heated at 110° C. for 24-48 h. This introduced a modified surface to the microfluidic device, where the modified surface had a structure of Formula I: 
     
       
         
         
             
             
         
       
     
     After cooling to room temperature and introducing argon to the evacuated chamber, the microfluidic device was removed from the reactor. The microfluidic device having the functionalized surface was rinsed with at least 250 microliters of deionized water, and was ready for further use. 
     Example 9. Introduction of a T-Cell Activating Surface within a Microfluidic Device 
     A. 
     The internal surfaces of an OptoSelect microfluidic device were covalently modified to include azido moieties as in Example 8 (Formula I). To functionalize the surface with streptavidin, the OptoSelect microfluidic device is first flushed repeatedly with 100% carbon dioxide, and then loaded with DBCO-streptavidin solution having a concentration from about 0.5 to about 2 micromolar, as produced in Example 4. After incubation for 15-30 minutes, during which the DBCO and azide groups coupled, the OptoSelect microfluidic device is washed repeatedly with 1×PBS to flush unbound DBCO-modified streptavidin. 
     This streptavidin surface is then further modified with biotinylated pMHC, and a selection of biotinylated anti CD28, biotinylated anti CD2 or any combination thereof. These molecules are suspended in PBS with 2% Bovine Serum Albumin at concentrations of about 1-10 micrograms/mL, in a ratio of pMHC molecules to antiCD28/antiCD2 from about 2:1 to about 1:2. This solution is perfused through the OptoSelect microfluidic device having streptavidin functionalized surfaces, facilitating conjugation to the surface. After one hour of incubation, the OptoSelect microfluidic device is flushed with PBS or media prior to loading cells. 
     B. 
     Alternatively, biomolecules of interest are conjugated via biotin modification of the biomolecules to streptavidin prior to reaction with the azido-modified surfaces of the OptoSelect microfluidic device. DBCO-streptavidin and biotinylated biomolecule are prepared separately in PBS solution at concentrations in the range of 0.5-2 micromolar, then mixed at any desired ratio, as described below. After allowing the biotinylated biomolecules to conjugate to the streptavidin for at least 15 minutes, this complex is used to modify the surface of an azido-modified OptoSelect microfluidic device as described above. 
     Cells may be imported into the microfluidic device having at least one antigen-presenting inner surface and activated during periods of culturing similarly as described for activation of T cells with antigen-presenting beads of Example 19. 
     Example 10. Covalent Modification and Functionalization of Silica Beads 
     10A. Silica Beads Having Covalent PEG 3 Disulfide Biotin Linked to Streptavidin 
     Spherical silica beads (2.5 micron, G biosciences Catalog #786-915, having a substantially simple spherical volume, e.g. the surface area of the bead is within the range predicted by the relationship 4πr 2 +/−no more than 10%) were dispersed in isopropanol, and then dried. The dried beads were treated in an oxygen plasma cleaner (Nordson Asymtek) for 5 min, using 100 W power, 240 mTorr pressure and 440 sccm oxygen flow rate. The cleaned beads were treated in a vacuum reactor with (11-azidoundecyl) trimethoxy silane (300 microliters) in a foil boat in the bottom of the vacuum reactor in the presence of magnesium sulfate heptahydrate (0.5 g, Acros Cat. #10034-99-8), as a water reactant source in a separate foil boat in the bottom of the vacuum reactor. The chamber was then pumped to 750 mTorr using a vacuum pump and then sealed. The vacuum reactor was placed within an oven heated at 110° C. for 24-48 h. This introduced a covalently modified surface to the beads, where the modified surface had an azide functionalized structure of Formula I: 
     
       
         
         
             
             
         
       
     
     After cooling to room temperature and introducing argon to the evacuated chamber, the covalently modified beads were removed from the reactor. The beads having a covalently modified surface functionalized with azide reactive moieties were rinsed with acetone, isopropanol, and dried under a stream of nitrogen. The covalently modified azide functionalized beads were dispersed at a concentration of 1 mg/20 microliters in a 5.7 mM DMSO solution of dibenzylcyclooctynyl (DBCO)S-S biotin modified-PEG3 (Broadpharm, Cat. # BP-22453) then incubated at 90° C./2000 RPM in a thermomixer for 18 hours. The biotin modified beads were washed three times each in excess DMSO, then rinsed with PBS. The biotin modified beads in PBS were dispersed in PBS solution containing approximately 30 micromoles/700 microliter concentration streptavidin. The reaction mixture was shaken at 30° C./2000 RPM in a thermomixer for 30 minutes. At the completion of the reaction period, the covalently modified beads presenting streptavidin were washed three times in excess PBS. FTIR analysis determined that SAV was added to the surface (Data not shown). The disulfide containing linker may be particularly useful if cleavage from the surface may be desirable. The disulfide linker is susceptible to cleavage with dithiothreitol at concentrations that were found to be compatible with T lymphocyte viability (Data not shown). 
     10B. Silica Beads Having Covalent PEG4 Biotin Linked to Streptavidin Diluted with PEG5-Carboxylic Acid Surface-Blocking Molecular Ligands. 
     Beads having a covalently modified surface functionalized with azide reactive moieties of Formula 1, prepared as above in Example 10A, were rinsed with acetone, isopropanol, and dried under a stream of nitrogen. The covalently modified azide functionalized beads were dispersed at a concentration of 1 mg/10 microliters in a DMSO solution of 0.6 mM dibenzylcyclooctynyl (DBCO)-modified-PEG4-biotin (Broadpharm, Cat. # BP-22295), 5.4 mM dibenzylcyclooctynyl (DBCO)-modified-PEG5-carboxylic acid (Broadpharm, Cat. # BP-22449), and 100 mM sodium iodide then incubated at 30° C./1,000 RPM in a thermomixer for 18 hours. The biotin modified beads were washed three times each in excess DMSO, then rinsed with PBS. The biotin modified beads in PBS were dispersed in PBS solution containing approximately 10 nanomoles/1 milliliter concentration streptavidin. The reaction mixture was shaken at 30° C./1000 RPM in a thermomixer for 30 minutes. At the completion of the reaction period, the covalently modified beads presenting streptavidin were washed three times in excess PBS. FTIR analysis determined that SAV was added to the surface (Data not shown). 
     Example 11. Preparation of an Antigen Presenting Surface of a Polymeric Bead 
     Streptavidin functionalized (covalently coupled) convoluted spherical polymeric beads (e.g., the actual surface area of the bead is greater than the relationship surface area=4πr 2 +/−no more than 10%, DynaBeads™ (ThermoFisher Catalog #11205D, bead stock at 6.67e8/mL)) were delivered (15 microliters; 1e7 beads) to a 1.5 mL microcentrifuge tube with 1 mL of Wash Buffer (DPBS (No Magnesium +2 , No Calcium +2 , 244 mL); EDTA (1 ml, final concentration 2 mM); and BSA (5 ml of 5%, final concentration 0.1%), and separated using a magnetic DynaBead rack. The wash/separation with 1 mL of the Wash Buffer was repeated, and a further 200 microliters of Wash Buffer was added with subsequent pulse centrifugation. Supernatant Wash Buffer was removed. 
     Wash Buffer (600 microliters) containing 1.5 micrograms biotinylated Monomer MHC (HLA-A*02:01 MART-1 (MBL International Corp., Catalog No. MR01008, ELAGIGILTV) was dispensed into the microcentrifuge tube, and the beads were resuspended by pipetting up and down. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixture was pipetted up and down again. The tube was pulse centrifuged and the supernatant liquid removed, and the tube was placed within the magnetic rack to remove more supernatant without removing beads. 
     A solution of biotinylated anti-CD28 (Miltenyi Biotec, Catalog #130-100-144, 22.5 microliters) in 600 microliters Wash Buffer was added to the microcentrifuge tube. The beads were resuspended by pipetting up and down. The beads were incubated at 4° C. for 30 min, resuspending after 15 min with another up and down pipetting. At the end of the incubation period, the tube was briefly pulse centrifuged. After placing back into the magnetic rack, and allowing separation for 1 min, the Buffer solution was aspirated away from the functionalized beads. The MHC monomer/anti-CD28 antigen presenting beads were resuspended in 100 microliters Buffer Wash, stored at 4° C., and used without further manipulation. The 1e7 2.80 micron diameter functionalized DynaBeads have a nominal (ideal predicted surface area of a sphere) surface area of about 24e6 square microns available for contact with T lymphocyte cells. However, the convolutions of this class of polymeric bead which are not necessarily accessible by T lymphocyte cells, are also functionalized in this method. Total ligand count may not reflect what is available to contact and activate T lymphocyte cells. 
     The MHC monomer/anti-CD28 antigen presenting beads were characterized by staining with Alexa Fluor 488-conjugated Rabbit anti Mouse IgG (H+L) Cross-adsorbed secondary antibody (Invitrogen Catalog # A-11059) and APC-conjugated anti-HLA-A2 antibody (Biolegend Catalog #343307), and characterized by flow cytometry. 
     Example 12. Activation of CD8+ T Lymphocytes by Antigen Presenting Beads Compared to Activation CD8+ T Lymphocytes by Dendritic Cells 
     Cells: CD8+ T lymphocytes were enriched in a medium including RPMI plus 10% fetal bovine serum (FBS) from commercially available PBMCs following manufacturers directions for EasySep™ Human CD8 Positive Selection Kit II, commercially available kit from StemCell Technologies Canada Inc. (Catalog #17953), by negative selection. 
     Dendritic cells: were generated from autologous PBMCs. Autologous PBMCs (10-50 e6) were thawed into 10 mL of pre-warmed RPMI media including 10% FBS. Cells were pelleted by centrifuging for 5 mins at 400×g. Cells were resuspended in RPMI and counted. 
     The cells were enriched for monocytes using negative bead isolation (EasySep™ Human Monocyte Isolation Kit, StemCell Technologies, Catalog #19359), according to manufacturers instructions. The resulting monocytes were counted, providing about a 5% yield, and then plated at 1.5-3 e6 cells per 3 mL per well in AIM-V® Medium (ThermoFisher Catalog #12055091) containing 17 ng/mL IL-4 and 53 ng/mL Human Granulocyte Macrophage Colony-Stimulating Fact (GM-CSF, ThermoFisher Catalog # PHC2013)). The cells were incubated for a total of 6 days at 37° C. At Day 2 and Day 4, 100 microliters of feeding media (AIM-V® Medium plus IL-4 (167 U/mL) and GM-CSF (540 ng/mL)) was added to each well, and incubation was continued. 
     On Day 6, 0.5 mL of a maturation cocktail was added to each well. The maturation cocktail included 10 ng/mL TNF-alpha; 2 ng/mL IL-1B; 1000 U/mL IL-6, 1000 ng/mL PGE2; 167 U/mL IL-4 and 267 U/mL GM-CSF in AIM-V® Medium. The cells were incubated for a further 24 h at 37° C. Mature DCs were then collected from the maturation medium, counted, and prepared for further use. The DCs were characterized by staining for CD3 (BD Catalog #344828), DC-SIGN (CD209, Biolegend Catalog #330104), CD14 (Biolegend Catalog #325608), CD86 (BD Catalog #560359), Fc Block (BioLegend Catalog #422302), and viability (BD Catalog #565388); suspended in FACS buffer; and examined by FACS flow cytometry. 
     Dendritic cells presenting antigen were prepared by plating at a concentration of 2e6/mL in 1% HSA, and pulsing with antigen (MART1 peptide, Anaspec, custom synthesis, 40 micrograms/mL) and beta2-microglobulin (Sigma Aldrich Catalog # M4890, 3 micrograms/mL), and then culturing with agitation for 4 h. The pulsed DCs were irradiated in a Faxitron CellRad® x-ray cell irradiator for 30 min before use, with a target dose of 50 greys. 
     Culture medium and diluent for reagent additions: Advanced RPMI (ThermoFisher Catalog #12633020, 500 mL); 1× GlutaMAX (ThermoFisher Catalog #35050079, 5 mL); 10% Human AB serum (zen-bio, Catalog # HSER-ABP 100 mL, 50 mL); and 50 nM beta-mercaptoethanol (ThermoFisher Catalog #31350010, 50 nm stock, 0.5 mL, final conc 50 micromolar). 
     Experimental Setup: For each activating species, a single 96-well tissue-culture treated plate (VWR Catalog #10062-902) was used (wellplate 1 (DCs); wellplate 2 (Antigen presenting beads)). CD8+ T lymphocytes (2e5) (80-90% pure) were added to each individual well. 
     Pulsed DCs were added at 5e3 for each well in wellplate 1, yield a 1:40 ratio of DCs: CD8+ T lymphocytes. 
     Antigen presenting surface polymeric beads (2e5), prepared as in Example 11, presenting pMHC including MART1 and anti-CD28 antibody, were added to each of the wells in wellplate 2. pMHC was loaded at 1.5 micrograms/1e7 beads. Anti-CD 28 antibody was loaded on the beads at three different levels: 0.25 micrograms/1e7 beads; 0.75 micrograms/1e7 beads; and 2.25 micrograms/1e7 beads. 
     Each wellplate was cultured at 37° C. On day 0, IL-21 (150 ng/milliliter) in CTL media, was added to each well of wellplates 1 and 2, providing a final concentration in each well of 30 ng/mL. On day 2, IL21 was added to each well of the wellplates, to a final concentration of 30 ng/mL. Culturing was continued to day 7. 
     Day 7. A subset of wells from each wellplate was individually stained for MHC tetramer (Tetramer PE, MBL Catalog # T02000, 1 microliter/well), CD4 (Biolegend Catalog #300530, 0.5 microliters/well); CD8 (Biolegend Catalog #301048, 0.5 microliters/well); CD28 (Biolegend Catalog #302906, 0.31 microliters/well); CD45RO (Biolegend Catalog #304210, 0.63 microliters/well); CCR7 (CD197, Biolegend Catalog #353208, 0.5 microliters/well); and viability (BD Catalog #565388, 0.125 microliters/well). Each well was resuspended with 150 microliters FACS buffer and 10 microliters of Countbright™ beads (ThermoFisher Catalog # C36950). FACS analysis was performed on a FACSCelesta™ flow cytometer (BD Biosciences).  FIG. 10  shows the zebra plots for the flow cytometry analyses for CD8/MART1 phenotypes. For each row of zebra plots,  1010 ,  1020 ,  1030 , and  1040 , the left hand plot is a representative negative well, and the right hand plot is a representative positive well. Row  1010  are wells from the DC stimulated well plate. Rows  1020 ,  1030 , and  1040  show results from the antigen-presenting bead stimulated well plate. Row  1020  shows the results for 0.25 micrograms/1e7 beads of anti-CD28 antibody loading and 1.5 micrograms//1e7 beads of pMHC. Row  1030  shows the results for 0.75 micrograms/1e7 beads anti CD28 antibody loading and 1.5 micrograms/1e7 beads of pMHC. Row  1040  shows the results for 2.25 micrograms/1e7 beads anti CD28 antibody loading and 1.5 micrograms/1e7 beads of pMHC. It can be seen that the antigen presenting beads initiate activation in a dose/responsive manner when varying the levels of anti-CD28 antibody, and that the MHC peptides loaded with MART1 are sufficient in combination with the anti-CD28 loading to activate T lymphocytes similarly to that of DCs. 
     Day 7. Restimulation. A second aliquot of pulsed DCs or antigen presenting beads, respectively, was delivered to each occupied well in wellplate 1 and wellplate 2. IL21 was added to each well of the wellplate to a final concentration of 30 ng/mL. Culturing was continued. 
     Day 8. Addition of 50 microliters of IL-2 (50 IU/mL) and IL-7 (25 ng/mL) was made to each well in wellplate 1 and wellplate 2 to provide a final concentration of 10 IU/mL and 5 ng/mL respectively. Culturing was continued. 
     Day 9. Addition of 50 microliters of IL-21(150 ng/mL) was made to each occupied well of wellplate 1 and wellplate 2 to a final concentration of 30 ng/mL. Culturing was continued. 
     Day 14. A second subset of wells from each wellplate was individually stained and FACS sorted as described for the analysis on Day 7. The flow cytometry results are shown in  FIG. 11 . For each row  1110 ,  1120 ,  1130 ,  1140  has a representative Less Positive Well (left hand graph of each row) and a Highly Positive Well (right hand graph of each row). Row  1110  shows the amount of activation resulting from DC activation. Rows  1120 ,  1130 , and  1140  represent results for the increasing amounts of anti-CD 28 as discussed for the 7 day results. Row  1120  shows the results for 0.25 micrograms/1e7 beads of anti-CD28 antibody loading and 1.5 micrograms/1e7 beads of pMHC. Row  1130  shows the results for 0.75 micrograms/1e7 beads anti CD28 antibody loading and 1.5 micrograms/1e7 beads of pMHC. Row  1140  shows the results for 2.25 micrograms/1e7 beads anti CD28 antibody loading and 1.5 micrograms/1e7 beads of pMHC. It is notable that for antigen-presenting beads having increasing amounts of costimulatory ligands, there are no wells having no antigen specific T cells. Particularly at the 0.75 microgram and 2.25 microgram CD28 antibody loading levels (Rows  1130  and  1140 ), there are more significant numbers of antigen specific T cells than for the DC pulsed wells (Row  1110 ). 
       FIG. 12  shows tabularized results from these experiments. Row  1210  shows graphical representations of T cell activation characterization at Day 7. Row  1220  shows graphical representation of T cell activation characterization at Day 14. From left to right in each row, the y axis represents percentage of antigen specific T cells; total number of antigen specific T cells; antigen specific T cell fold expansion; and % of CD28 highly expressing cells within the antigen-specific T cell population. The x-axis for each graph shows the data set of each of DC, 0.25 microgram CD28 loaded beads, 0.75 microgram CD28 beads, and 2.25 microgram CD28 loaded beads. The antigen presenting bead stimulated activation appears to be initially slower than DC stimulation but production reached the same level by the end of the second culturing period. The phenotypic results show a good specificity of activation using the antigen presenting beads.  FIG. 12  shows equivalent levels of MART 1 activated T lymphocytes in the antigen presenting bead initiated examples compared to the DC stimulated examples. However, using dendritic cells as activating species, there are wells that have no activated T lymphocytes after 14 days. Therefore, antigen-presenting bead activation provides more controllable and reproducible activation than dendritic cells. 
     Third Period of Culturing. 
     In another experiment, where antigen presenting surfaces on beads were used as described in the immediately preceding paragraphs, but where comparison was not made with DCs, a third period of stimulation and culturing was performed. Day 14 to Day 21. Restimulation and feeding was performed as above for Day 7-Day 14, during continuation of culture conditions until Day 21. On Day 21, a last subset of wells from each wellplate was individually stained and FACS sorted as described for the analysis on Day 7. Additional activation was observed for the extended third stimulation sequence (Data not shown). 
     Example 13. Preparation of Covalently Functionalized Glass Beads 
     Silica beads (2.5 micron, G biosciences Catalog #786-915, having a substantially simple spherical surface, e.g. the surface area of the bead is within the range predicted by the relationship 4πr 2 +/−no more than 10%) were dispersed in isopropanol, and then dried. The dried beads were treated in an oxygen plasma cleaner (Nordson Asymtek) for 5 min, using 100 W power, 240 mTorr pressure and 440 sccm oxygen flow rate. The cleaned beads were treated in a vacuum reactor with (11-azidoundecyl) trimethoxy silane (300 microliters) in a foil boat in the bottom of the vacuum reactor in the presence of magnesium sulfate heptahydrate (0.5 g, Acros Cat. #10034-99-8), as a water reactant source in a separate foil boat in the bottom of the vacuum reactor. The chamber was then pumped to 750 mTorr using a vacuum pump and then sealed. The vacuum reactor was placed within an oven heated at 110° C. for 24-48 h. This introduced a covalently linked surface presenting reactive azide moieties to the beads, where the modified surface has a structure of Formula I. 
     After cooling to room temperature and introducing argon to the evacuated chamber, the intermediate reactive azide presenting beads were removed from the reactor and were rinsed with acetone, isopropanol, and dried under a stream of nitrogen. The azide presenting reactive beads (50 mg) were dispersed in 500 microliters DMSO with vigorous vortexing/brief sonication. The beads were pelleted, and 450 microliters of the DMSO were aspirated away from the beads. The pellet, in the remaining 50 microliters DMSO was vortexed vigorously to disperse. DBCO-SAV (52 microliters of 10 micromolar concentration, Compound 1) as synthesized in Example 3, having a PEG13 linker, was added. The beads were dispersed by tip mixing, followed by vortexing. 398 microliters of PBS with 0.02% sodium azide solution was added, followed by additional vortexing. The reaction mixture was incubated overnight on a thermomixer at 30° C., 1000 RPM. 
     After 16 hrs, 10 microliters of 83.7 mM DBCO-PEG5-acid were added to each sample and they were incubated an additional 30 minutes at 30° C./1,000 RPM. The beads were washed  3 X in PBS/azide, then suspended in 500 microliters of the same. 
     These covalently functionalized beads are modified to introduce primary activating molecules and co-activating molecules as described below in Example 18. 
     Example 14. Preparation of Covalently Functionalized Polystyrene Bead 
     Divinylbenzene-crosslinked polystyrene beads (14-20 micron, Cospheric Catalog #786-915) were dispersed in isopropanol, and then dried in a glass petri dish. The dried beads were treated in an oxygen plasma cleaner (Nordson Asymtek) for 40 seconds, using 100 W power, 240 mTorr pressure and 440 sccm oxygen flow rate. The cleaned beads were treated in a vacuum oven with (11-azidoundecyl) trimethoxy silane (Compound 5, 900 microliters) in a foil boat on the shelf of the oven in the presence of magnesium sulfate heptahydrate (1 g, Acros Cat. #10034-99-8), as a water reactant source in a separate foil boat on the same shelf of the oven. The oven was then pumped to 250 mTorr using a vacuum pump and then sealed. The oven was heated at 110° C. for 18-24 h. This introduced a covalently modified surface to the beads, where the modified surface had a structure of Formula I: 
     
       
         
         
             
             
         
       
     
     After pump-purging the oven three times, the covalently modified beads were removed from the oven and cooled. The covalently modified azide functionalized beads were dispersed at a concentration 15 mg/50 microliters in DMSO. To this, a 450 microliter solution of DBCO-labeled streptavidin (SAV) (Compound 1) at a concentration of 9.9 micromolar were added. The solution was then incubated at 30° C./1000 RPM in a thermomixer for 18 hours. The SAV modified beads were washed three times in PBS. FTIR analysis determined that SAV was added to the surface as shown in  FIG. 13 . 
       FIG. 13  shows superimposed FTIR traces of the functionalized bead as the covalently functionalized surface is built up. Trace  1310  showed the original unfunctionalized surface of the polystyrene bead. Trace  1320  showed the FTIR of the surface after introduction of the azide functionalized surface (having a structure of Formula I). Trace  1330  showed the FTIR of the surface after introduction of covalently linked PEG13-streptavidin surface to the polystyrene bead. Traces  1320  and  1330  showed introduction of FTIR absorption bands consistent with the introduction of each set of chemical species in the stepwise synthesis. 
     Example 15. Preparation of an Antigen Presenting Surface of a Bead with Anti-CD28 and Anti-CD2 
     Streptavidin functionalized (covalently coupled) DynaBeads™ (ThermoFisher Catalog #11205D), bead stock at 6.67e8/mL, convoluted (as described above) polymeric beads) were delivered (15 microliters; 1e7 beads) to 1.5 mL microcentrifuges tube with 1 mL of Wash Buffer (DPBS (No Magnesium +2 , No Calcium +2 , 244 mL); EDTA (1 ml, final concentration 2 mM); and BSA (5 ml of 5%, final concentration 0.1%), and separated using a magnetic DynaBead rack. The wash/separation with 1 mL of the Wash Buffer was repeated, and a further 200 microliters of Wash Buffer was added with subsequent pulse centrifugation. Supernatant Wash Buffer was removed. 
     Wash Buffer (600 microliters) containing 0.5 micrograms biotinylated Monomer MHC (HLA-A*02:01 MART-1 (MBL International Corp., Catalog No. MR01008, ELAGIGILTV) was dispensed into the microcentrifuge tubes, and the beads were resuspended by pipetting up and down. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were pulse-centrifuged and the supernatant liquid removed, and the tubes were placed within the magnetic rack to remove more supernatant without removing beads. 
     Solutions of biotinylated anti-CD28 (Biolegend, Catalog #302904) and biotinylated anti-CD2 (Biolegend, Catalog #300204) in 600 microliters Wash Buffer were added to the microcentrifuge tubes. Solutions contained a total of 3 micrograms of antibody. The solutions contained: 3 micrograms of anti-CD28 and 0 micrograms of anti-CD2, 2.25 micrograms of anti-CD28 and 0.75 micrograms of anti-CD2, 1.5 micrograms of anti-CD28 and 1.5 micrograms of anti-CD2, 0.75 micrograms of anti-CD28 and 2.25 micrograms of anti-CD2, or 0 micrograms of anti-CD28 and 3 micrograms of anti-CD2. The beads were resuspended by pipetting up and down. The beads were incubated at 4° C. for 30 min, then resuspended after 15 min with another up and down pipetting. At the end of the incubation period, the tube was briefly pulse centrifuged. After placing back into the magnetic rack, and allowing separation for 1 min, the Buffer solution was aspirated away from the functionalized beads. The MHC monomer/anti CD28 antigen presenting beads were resuspended in 100 microliters Buffer Wash, stored at 4° C., and used without further manipulation. The 1e7 2.80 micron diameter functionalized DynaBeads have a nominal surface area of about 24e6 square microns available for contact with T lymphocyte cells, but as described above, these convoluted spherical beads have a practical surface area of more than 10% above that of the nominal surface area. 
     Example 16. Preparation of Covalently Functionalized Polymeric Beads. Preparation of an Intermediate Reactive Synthetic Surface 
     In the first step of the manufacturing process, M-450 Epoxy-functionalized paramagnetic convoluted polymeric beads (DynaBeads™, ThermoFisher Cat. #14011 (convoluted having the same meaning as above)) were reacted with Tetrabutylammonium Azide to prepare polymeric beads presenting azide reactive moieties capable of reacting with functionalizing reagents having Click chemistry compatible reactive groups. 
     Example 17. Preparation of a Covalently Functionalized Synthetic Surface of a Bead 
     The azide-prepared convoluted beads from Example 16 were then reacted with dibenzocyclooctynyl (DBCO)-coupled Streptavidin to attach Streptavidin covalently to the polymeric beads. The DBCO-Streptavidin reagent was generated by reacting Streptavidin with amine-reactive DBCO-polyethylene glycol (PEG)13-NHS Ester, providing more than one attachment site per Streptavidin unit. 
     Further Reaction with Surface-Blocking Molecules. 
     The resulting covalently functionalized polymeric beads presenting streptavidin functionalities from Example 17 may subsequently be treated with DBCO functionalized surface-blocking molecules to react with any remaining azide reactive moieties on the polymeric bead. In some instances, the DBCO functionalized surface-blocking molecule may include a PEG molecule. In some instances, the DBCO PEG molecule may be a DBCO PEG5-carboxylic acid. Streptavidin functionalized polymeric beads including additional PEG or PEG-carboxylic acid surface-blocking molecules provide superior physical behavior, demonstrating improved dispersal in aqueous environment. Additionally, the surface-blocking of remaining azide moieties prevents other unrelated/undesired components present in this or following preparation steps or activation steps from also covalently binding to the polymeric bead. Finally, introduction of the surface-blocking molecular ligands can prevent surface molecules present on the T lymphocytes from contacting reactive azide functionalities. 
     Further Generalization. 
     It may be desirable to modify the azide functionalized surface of Example 16 with a mixture of DBCO containing ligand molecules. For example, DBCO-polyethylene glycol (PEG)13-streptavidin (Compound 1, prepared as in Example 3) may be mixed with DBCO-PEG5-COOH (surface-blocking molecules) in various ratios, and then placed in contact with the azide functionalized beads. In some instances, the ratio of DBCO-streptavidin molecules to DBCO-PEG5-COOH may be about 1:9; about 1:6, about 1:4 or about 1:3. Without wishing to be bound by theory, surface-blocking molecular ligands prevent excessive loading of streptavidin molecules to the surface of the bead, and further provide enhanced physico-chemical behavior by providing additional hydrophilicity. The surface-blocking molecules are not limited to PEG5-COOH but may be any suitable surface-blocking molecule described herein. 
     Example 18. Preparation of Covalently Modified Antigen Presenting Bead. Conjugation of Peptide-HLAs and Monoclonal Antibody Co-Activating Molecules 
     Materials: A. Antigen Bearing Major Histocompatibility Complex (MHC) I Molecule. 
     Biotinylated peptide-Human Leukocyte Antigen complexes (pMHC), were commercially available from MBL, Immunitrack or Biolegend. The biotinylated peptide-HLA complex included an antigenic peptide non-covalently bound to the peptide-binding groove of a Class I HLA molecule, which was produced and folded into the HLA complex at the manufacturer. The biotinylated peptide-HLA complex was also non-covalently bound to Beta2-Microglobulin. This complex was covalently biotinylated at the side chain amine of a lysine residue introduced by the BirA enzyme at a recognized location on the C-terminal peptide sequence of the HLA, also performed by the manufacturer. 
     B. Co-Activating Molecules 
     Biotinylated antibodies were used for costimulation and were produced from the supernatants of murine hybridoma cultures. The antibodies were conjugated to biotin through multiple amine functionalities of the side chains of lysines, randomly available at the surfaces of the antibodies. The biotinylated antibodies were commercially available (Biolegend, Miltenyi, or Thermo Fisher). 
     Biotinylated anti-CD28 useful in these experiments were produced from clone CD28.2, 15e8, or 9.3. 
     Biotinylated anti-CD2 useful in these experiments were produced from clone LT2 or RPA-2.10. Other clones may also be used in construction of covalently modified antigen presenting synthetic surfaces such as these polymeric beads. 
     Conjugation of the Primary Activating and Co-Activating Molecules to a Covalently Functionalized Surface of a Bead. 
     The MHC molecule (containing the antigenic molecule) and the co-activating molecules were conjugated to beads produced in a two-step process. In various experiments, the ratio of the co-activating molecules—in this case, biotinylated anti-CD28 and biotinylated anti-CD2—may be varied in a range from about 100:1 to about 1:100; or from about 20:1 to about 1:20. In other experiments, the ratio of the co-activating molecules was from about 3:1 to about 1:3 or about 1:1. See  FIGS. 14A-D . 
     Pmhc Loading. 
     Streptavidin functionalized (covalently coupled) DynaBeads™ (ThermoFisher Catalog #11205D), bead stock at 6.67e8/mL, convoluted (as described above) polymeric beads) were washed with Wash Buffer (Dulbecco&#39;s Phosphate-Buffered Saline without Calcium or Magnesium; 0.1% Bovine Serum Albumin; 2 mM Ethylenediaminetetraacetic Acid). Wash buffer was pipetted into a tube, to which the Streptavidin beads were added. Typically, ˜1e7 beads were pipetted into 1 mL of Wash Buffer. The beads were collected against the wall of the tube using a magnet (e.g., DYNAL DynaMag-2, ThermoFisher Cat. #12-321-D). After the beads migrated to the wall of the tube, the Wash Buffer was removed via aspiration, avoiding the wall to which the beads were held. This wash process was repeated twice more. After the third wash, the beads were resuspended at 1.67e7 beads/mL in Wash Buffer. 
     The beads were then mixed with pMHC. The pMHC was added to the beads in Wash Buffer at a final concentration of 0.83 micrograms of pMHC/mL. The beads and pMHC were thoroughly mixed by vortexing, then incubated at 4° C. for 15 minutes. The beads were again vortexed, then incubated at 4° C. for an additional 15 minutes. 
     Co-Activating Molecule Loading. 
     The pMHC-functionalized beads were again captured via magnet, and the pMHC reagent mixture removed by aspiration. The beads were then brought to 1.67e7/mL in Wash Buffer. Biotinylated Anti-CD28 and biotinylated anti-CD2 (if used) were then added to the beads at a final concentration of 5 micrograms/mL of total antibody. If both anti-CD28 and anti-CD2 were used, then each antibody was added at 2.5 micrograms/mL. 
     The beads and pMHC were thoroughly mixed by vortexing, then incubated at 4° C. for 15 minutes. The beads are again vortexed, then incubated at 4° C. for an additional 15 minutes. 
     After modification by the biotinylated antibodies, the beads were captured via magnet, and the antibody mixture was removed by aspiration. The beads were resuspended in Wash Buffer at a final density of 1e8 beads/mL. The beads were used directly, without further washing. 
     Characterization. 
     To assess the degree of loading and homogeneity of the resulting antigen-presenting beads, the beads were stained with antibodies that bind the pMHC and co-activating CD28/CD2 (if present) antibodies on the beads. The resulting amount of staining antibody was then quantified by flow cytometry. The number of pMHC and costimulatory antibodies on the beads was then determined using a molecular quantification kit (Quantum Simply Cellular, Bangs Labs) according to the manufacturer&#39;s instructions. 
     To analyze the beads, 2e5 beads were added to each of two microcentrifuge tubes with 1 mL of Wash Buffer. The pMHC quantification, and costimulation antibody quantification were performed in separate tubes. In each separate experiment, the beads were collected against the wall of the tube using a magnet, and the Wash Buffer removed. The beads were resuspended in the respective tubes in 0.1 mL of Wash Buffer, and each tube was briefly vortexed to separate the beads from the wall of the tube. To detect pMHC, 0.5 microliters of anti-HLA-A conjugated to APC (Clone BB7.2, Biolegend) was added to the first tube. The first tube was again vortexed briefly to mix the beads and detection antibody. To detect the costimulation antibodies, 0.5 microliters of anti-mouse IgG conjugated to APC was added to the second tube. Depending on the costimulation antibody clones used, different anti-mouse antibodies were used, e.g., RMG1-1 (Biolegend) is used to detect CD28.2 (anti-CD28) and RPA-2.10 (anti-CD2). The detection antibodies were incubated with the beads for 30 minutes in the dark at room temperature for each tube. 
     For each tube, the beads were then captured against the wall of the tube via magnet, and the staining solution was removed by aspiration. 1 mL of Wash Buffer was added to each tube, then aspirated to remove any residual staining antibody. The beads in each tube were resuspended in 0.2 mL of Wash Buffer and then the beads from each tube was transferred to a 5 mL Polystyrene tube, keeping the two sets of beads separate. 
     To quantify the loading of the different species, the beads were analyzed on a flow cytometer (FACS Aria or FACS Celesta, BD Biosciences). First, a sample of unstained product antigen-bearing beads is collected. A gate is drawn around the singlet and doublet beads. Doublet beads are discriminated from singlet beads based on their higher forward and side scatter amplitudes. Typically, approximately 10,000 bead events were recorded. The beads stained for pMHC and costimulation antibodies are then analyzed in separate experiments. Again, approximately 10,000 bead events were collected for each sample, and the APC median fluorescence intensity (MFI) and coefficient of variation of the APC MFI ( 100 *[Standard Deviation of the MFI]/[MFI]) of the singlet bead events was recorded. 
     To determine the number of pMHC and costimulation antibodies per bead, a molecular quantification kit is used. The kit (Quantum Simply Cellular (Bangs Laboratories) included a set of beads with specified antibody binding capacities (determined by the manufacturer). These beads are used to capture the detection antibody. Briefly, the quantification beads are incubated with saturating amounts of the detection binding, then washed thoroughly to remove excess antibody. The beads with different binding capacities are mixed, along with negative control beads and resuspended in Wash Buffer. The mixed beads are then analyzed by Flow Cytometry. The APC MFI of each bead with specified binding capacity is recorded, and a linear fit of the MFI vs binding capacity is generated. The MFI of the aAPCs is then used to determine the number of detection antibodies bound per aAPC. This number is equal to the number of (pMHC or costimulation) antibodies on the bead. The following table shows results for: 
     A. Antigen-presenting convoluted polymeric beads produced in Examples 16-17 and functionalized above in this experiment. 
     B. Antigen-presenting substantially spherical silica beads as produced in Example 10B 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                   
                 Target 
               
               
                   
                   
                   
                   
                 antibodies 
               
               
                   
                   
                 Ligands/ 
                 Ligands/sq 
                 (ug)/mg 
               
               
                 Condition 
                 Labeling 
                 Bead 
                 um 
                 beads 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 A. Polymeric 
                 HLA 
                 487209 
                 19781 
                 8.1 
               
               
                 bead 
               
               
                 A. Polymeric 
                 Costim 
                 426992 
                 17336 
                 7.1 
               
               
                 bead 
               
               
                 B. 4 micron 
                 HLA 
                 604471 
                 12026 
                 2.35 
               
               
                 monodisperse 
               
               
                 silica (10B) 
               
               
                 B. 4 micron 
                 Costim 
                 760489 
                 15129 
                 2.96 
               
               
                 monodisperse 
               
               
                 silica (10B) 
               
               
                   
               
            
           
         
       
     
     Example 19. Stimulation by Antigen-Presenting Beads 
     Input Cell Populations. 
     To increase the number of antigen-specific, CD8+ T cells plated per well, CD8+ T cells were first isolated from Peripheral Blood Mononuclear Cells using commercially available reagents. The cells can be isolated using negative selection, e.g., EasySep™ Human CD8+ T Cell Isolation Kit (StemCell Technologies) or by positive selection, e.g., CliniMACS CD8 Reagent (Miltenyi Biotec). The CD8+ T cells were isolated according to the manufacturers recommended protocol. Alternatively, different subsets of T cells can be isolated, e.g., Naïve CD8+ T cells only, or a less-stringent purification can be performed, e.g., depletion of Monocytes by CliniMACS CD14 Reagent (Miltenyi Biotec). Alternatively, if T cells specific for a Class II-restricted antigen are desired, CD4+ T cells can be isolated by corresponding methods. 
     First T Cell Stimulation Period. 
     The enriched CD8+ T cells were resuspended at 1e6/mL in media with IL-21 at 30 nanograms/mL (R&amp;D Systems). The media used for T cells was Advanced RPMI 1640 Medium (Thermo Fisher) supplemented with 10% Human AB Serum (Corning CellGro) plus GlutaMax (Thermo Fisher) and 50 micromolar Beta-MercaptoEthanol (Thermo Fisher) or ImmunoCult™-XF T Cell Expansion Medium (StemCell Technologies). 
     Antigen-presenting beads were prepared as described in Example 18, where the convoluted polymeric beads were loaded at a final concentration of 0.83 micrograms of pMHC/mL. The resulting lot of beads was split into five portions, loading the costimulating ligands in the following proportions: 
     Set 1: CD28 at 3.00 micrograms/mL and CD2 at zero concentration. 
     Set 2: CD28 at 2.25 micrograms/mL and CD2 at 0.75 micrograms/mL. 
     Set 3: CD28 at 1.50 micrograms/mL and CD2 at 2.25 micrograms/mL. 
     Set 4: CD28 at 0.75 micrograms/mL and CD2 at 2.25 micrograms/mL. 
     Set 5: CD28 at 0.00 micrograms/mL and CD2 at 3.00 micrograms/mL. 
     To the T cells in media, an aliquot of each set of antigen-presenting beads were added to separate wells to a final concentration of 1 antigen-presenting bead per cell. The cells and antigen-presenting beads were mixed and seeded into tissue culture-treated, round-bottom, 96-well microplates. 0.2 mL (2e5 cells) was added to each well of the plate, which was then placed in a standard 5% 002, 37° C. incubator. Typically, 48-96 wells were used per plate. Two days later, IL-21 was diluted to 150 nanograms/mL in media. 50 microliters of IL-21 diluted in media was added to each well, and the plate was returned to the incubator. 
     After culturing the cells for an additional 5 days (seven days total), the cells were analyzed for antigen-specific T cell expansion. Alternatively, the cells were-stimulated in a second stimulation period as described in the following paragraphs to continue expanding antigen specific T cells. 
     Second T Cell Stimulation Period. 
     From each well of the above well plate at the conclusion of the first stimulation period, 50 microliters of media were removed, being careful not to disturb the cell pellet at the bottom of the well. IL-21 was diluted to 150 ng/mL in fresh media, and the antigen-presenting beads as produced above were added to the IL-21/media mixture at a final density of 4e6 antigen-presenting beads/mL. 50 microliters of this IL-21/antigen-presenting bead/media mixture was added to each well, resulting in an additional 2e5 antigen-presenting beads being added to each well. Optionally, the wellplate can be centrifuged for 5 minutes at 400×g to pellet the antigen-presenting beads onto the cells. The wellplate was returned to the incubator. 
     The next day (8 days from start of stimulation experiments), the wellplate was removed from the incubator, and 50 microliters of media was removed from each well. IL-2 (R&amp;D Systems) was diluted into fresh media to 50 Units/mL. To this, media containing IL-2, IL-7 (R&amp;D Systems) was added to a final concentration of 25 ng/mL. 50 microliters of this IL-2/IL-7/media mixture was added to each well, and the wellplate was returned to the incubator. 
     The following day (9 days from start of stimulation experiments), the wellplate was removed from the incubator, and 50 microliters of media was again removed from each well. IL-21 was diluted into fresh media to 150 nanograms/mL. 50 microliters of this IL-21/media mixture was added to each well, and the wellplate was returned to the incubator. 
     After culturing the cells for an additional 5 days (14 days from the start of stimulation experiments), the cells were typically analyzed for antigen-specific T cell expansion. However, the cells can be re-stimulated with more antigen-presenting beads for another period of culturing as above to continue expanding antigen specific T cells. 
     Analysis of Antigen-Specific T Cell Stimulation and Expansion. 
     Once the desired number of T cell stimulations were performed, the cells were analyzed for expansion of T cells specific for the pMHC complex used to prepare the antigen-presenting beads. Antigen-specific T cells are detected using Phycoerythrin (PE) conjugated Streptavidin, which is bound to 4 pMHC complexes. These complexes are referred to as tetramers. Typically, a tetramer manufactured with the same peptide used in the pMHC of the antigen-presenting beads was used to detect the antigen-specific T cells. 
     To detect and characterize the antigen-specific T cells, a mixture of PE-tetramer (MBL, Intl) and antibodies specific for various cell surface markers with various fluorophores, e.g., FITC-conjugated anti-CD28, PerCP-Cy5.5-conjugated anti-CD8, was prepared in FACS Buffer (Dulbecco&#39;s Phosphate-Buffered Saline without Calcium or Magnesium; 2% Fetal Bovine Serum; 5 mM Ethylenediaminetetraacetic Acid, 10 mM HEPES). The amount of antibody used was determined by titration against standard cell samples. The surface markers typically used for characterization used are: CD4, CD8, CD28, CD45RO, CD127 and CD197. Additionally, a Live/Dead cell discrimination dye, e.g., Zombie Near-IR (Biolegend) and Fc Receptor blocking reagent, e.g., Human TruStain FcX™ (Biolegend) were added to distinguish live cells and prevent non-specific antibody staining of any Fc-Receptor expressing cells in the culture, respectively. 
     Typically, the wells were mixed using a multi-channel micro-pipettor, and 50 microliters of cells from each well were transferred to a fresh, non-treated, round-bottom, 96-well microplate. The cells were washed by addition of 0.2 mL of FACS buffer to each well. Cells were centrifuged at 400×g for 5 minutes at room temperature, and the wash removed. To each well, 25 microliters of the Tetramer, Antibody, Live/Dead, Fc blocking reagent mixture was added. The cells were stained for 30 minutes under foil at room temperature. The cells were then washed again, and finally resuspended in FACS Buffer with CountBright Absolute Counting Beads (Thermo Fisher). The cells were then analyzed by Flow Cytometry (FACS Aria or FACS Celesta, BD Biosciences). The frequency of antigen-specific T cells was determined by gating first on Single/Live cells, then gating on CD8 + /Tetramer +  cells. Appropriate gating conditions were determined from control stains, such as a negative control Tetramer with no known specificity (MBL, Intl) or antibody isotype controls. Within the antigen-specific T cell population, the frequency of CD45RO+/CD28 High  cells was determined, as well as the number of cells expressing CD127. Activated T cells, which express CD45RO, that continue to express high levels of CD28 and CD127 have been shown to include memory precursor effector cells. Memory precursor cells have been shown to be less differentiated and have higher replicative potential than activated T cells that do not express these markers. 
       FIG. 14A : The frequency of MART1-specific T cells (percent of live cells) 7 days after stimulation with antigen-presenting beads prepared with the indicated amount (in micrograms) of anti-CD28 and/or anti-CD2. Each point represents a well of a 96-well microplate. Data is pooled from two independent experiments. 
       FIG. 14B : The total number of MART1-specific T cells 7 days after stimulation with antigen-presenting beads prepared with the indicated amount (in micrograms) of anti-CD28 and/or anti-CD2. Each point represents a well of a 96-well microplate. Data is pooled from two independent experiments. 
       FIG. 14C : The fold expansion of MART1-specific T cells 7 days after stimulation with aAPCs prepared with the indicated amount (in micrograms) of anti-CD28 and/or anti-CD2. Each dot represents a well of a 96-well microplate. Data was pooled from two independent experiments. Fold expansion is calculated by dividing the frequency of MART1 T cells in each well at day 7 by the frequency of MART1 T cells in the sample at day 0. 
       FIG. 14D : The fraction of MART1-specific T cells that were positive for CD45RO and expressing high levels of CD28 7 days after stimulation with aAPCs prepared with the indicated amount (in micrograms) of anti-CD28 and/or anti-CD2. Each dot represents a well of a 96-well microplate. Data was pooled from two independent experiments. Fold expansion is calculated by dividing the frequency of MART1 T cells in each well at day 7 by the frequency of MART1 T cells in the sample at day 0. 
     It was observed that production of antigen specific T cells was possible with a wide range of proportions of the costimulatory ligands anti-CD28 and anti-CD2. Production was possible using only one of the two costimulatory ligands. However, a combination of anti-CD28 and anti-CD2, including at ratios of anti-CD28:anti-CD2 from about 3:1 to about 1:3, provided increased measurements of each of the above characteristics. 
       FIGS. 15A-15E : For T cells stimulated as described above, using the SLC45A2 antigen in the antigen-presenting beads produced as described above, exemplary Flow Cytometry graphs are shown.  FIG. 15A  showed the results of T cells, prior to stimulation (“Input”). Representative stimulated wells are shown in the lower panels: Negative growth well ( FIG. 15B ); intermediate growth well ( FIG. 15C ); High growth well ( FIG. 15D ); and Irrelevant Tetramer staining ( FIG. 15E ). 
       FIG. 16 : For T cells stimulated as described above, using the NYESO1 antigen, the frequency of T cells positive for CD45RO and expressing high levels of CD28 are shown respectively after a single period of stimulation (7 days, left column) and after two periods of stimulation as described above (14 days, right column). Increased frequency of antigen specific activated T cells were observed. 
     Cytotoxicity: 
     Killing of target tumor cells and non-target tumor cells by SLC45A2-specific T cells expanded using Dendritic cells pulsed with SLC45A2 antigen (DCs, Black bars) or antigen-presenting beads (presenting SLC45A2 antigen) produced as described above (gray hatched bars). See  FIG. 17 . Killing was measured by activation of Caspase-3 in target cells. MEL526 tumor cells express SLC45A2 and were killed by T cells expanded using both DCs and the antigen-presenting beads. A375 cells do not express SLC45A2 and were not killed by T cells expanded using DCs or the antigen-presenting beads. The antigen-presenting beads performed as well as the Dendritic cells. 
       FIGS. 18A-18C  show the comparison between the cell product of the dendritic cell stimulation and the antigen-presenting bead stimulated cell product.  FIG. 18A  showed that the percentage of Antigen Specific (AS) activated T cells is higher in the antigen-presenting bead stimulation experiment.  FIG. 18B  showed that the cell product of the antigen-presenting bead stimulation experiment has higher percentages of the desired CD45RO positive/highly CD28 positive phenotype, compared to that of the dendritic cell stimulated cell product.  FIG. 18C  showed that the actual numbers of antigen-specific T cells is higher in the cell product produced by the antigen-presenting bead stimulation experiment. Overall, antigen-presenting bead stimulation provides a more desirable cell product, and is a more controllable and cost effective method of activating T cells than the use of dendritic cell activation. 
     Example 20. Preparation of an Antigen-Presenting Bead Having Protein Fragment Co-Activating Ligands 
     20A. Preparation of an antigen presenting surface of a bead with lysine-biotinylated CD80 and CD58 
     Streptavidin functionalized (covalently coupled, convoluted (as described above) polymeric) DynaBeads™ (ThermoFisher Catalog #11205D, bead stock at 6.67e8/mL) were delivered (15 microliters; 1e7 beads) to 1.5 mL microcentrifuges tube with 1 mL of Wash Buffer (DPBS (No Magnesium +2 , No Calcium +2 , 244 mL); EDTA (1 ml, final concentration 2 mM); and BSA (5 ml of 5%, final concentration 0.1%), and separated using a magnetic DynaBead rack. The wash/separation with 1 mL of the Wash Buffer was repeated, and a further 200 microliters of Wash Buffer was added with subsequent pulse centrifugation. Supernatant Wash Buffer was removed. 
     Wash Buffer (600 microliters) containing 0.5 micrograms biotinylated Monomer MHC (HLA-A*02:01 SLC45A2 (Biolegend, Custom Product, SLYSYFQKV) was dispensed into the microcentrifuge tubes, and the beads were resuspended by pipetting up and down. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were pulse centrifuged and the supernatant liquid removed, and the tubes were placed within the magnetic rack to remove more supernatant without removing beads. 
     A solution of biotinylated recombinant CD80 protein (R&amp;D Systems, Custom Product) and biotinylated recombinant CD58 (R&amp;D Systems, Custom Product) in 600 microliters Wash Buffer was added to the microcentrifuge tubes. The CD80 was prepared as an N-terminal fusion to a human IgG1 Fc domain and biotinylated on random Lysine residues by the manufacturer. The CD58 was biotinylated in the same manner. The solution contained a total of 4.5 micrograms of CD80 and 1.5 micrograms of CD58. The beads were resuspended by pipetting up and down. The beads were incubated at 4 C for 30 min, resuspending after 15 min with another up and down pipetting. At the end of the incubation period, the tube was briefly pulse centrifuged. After placing back into the magnetic rack, and allowing separation for 1 min, the Buffer solution was aspirated away from the functionalized beads. The MHC monomer/CD80/CD58 antigen presenting beads were resuspended in 100 microliters Wash Buffer, stored at 4° C., and used without further manipulation. The 1e7 2.80 micron diameter functionalized DynaBeads have a nominal surface area of about 24e6 square microns available for contact with T lymphocyte cells, which, as described herein, does not reflect the total surface occupied by pMHC and costimulatory molecular ligands. 
     20B. Preparation of an Antigen Presenting Surface of a Bead with BirA Biotinylated CD80 and CD58 
     Streptavidin functionalized (covalently coupled, convoluted (as described above) polymeric) DynaBeads™ (ThermoFisher Catalog #11205D, bead stock at 6.67e8/mL) were delivered (15 microliters; 1e7 beads) to 1.5 mL microcentrifuges tube with 1 mL of Wash Buffer (DPBS (No Magnesium +2 , No Calcium +2 , 244 mL); EDTA (1 ml, final concentration 2 mM); and BSA (5 ml of 5%, final concentration 0.1%), and separated using a magnetic DynaBead rack. The wash/separation with 1 mL of the Wash Buffer was repeated, and a further 200 microliters of Wash Buffer was added with subsequent pulse centrifugation. Supernatant Wash Buffer was removed. 
     Wash Buffer (600 microliters) containing 0.5 micrograms biotinylated Monomer MHC (HLA-A*02:01 MART1 (Biolegend, Custom Product, ELAGIGILTV) was dispensed into the microcentrifuge tubes, and the beads were resuspended by pipetting up and down. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were pulse centrifuged and the supernatant liquid removed, and the tubes were placed within the magnetic rack to remove more supernatant without removing beads. 
     A solution of biotinylated recombinant CD80 protein (BPS Biosciences, Catalog Number 71114) and biotinylated recombinant CD58 (BPS Biosciences, Catalog Number 71269) in 600 microliters Wash Buffer was added to the microcentrifuge tubes. The recombinant proteins were prepared as N-terminal fusions to a human IgG1 Fc domain, with a final C-terminal BirA biotinylation site, and biotinylated by the manufacturer. The solution contained a total of 1.5 micrograms of recombinant CD80 and 1.5 micrograms of recombinant CD58 proteins. The beads were resuspended by pipetting up and down. The beads were incubated at 4° C. for 30 min, then resuspended after 15 min with another up and down pipetting. At the end of the incubation period, the tube was briefly pulse centrifuged. After placing back into the magnetic rack, and allowing separation for 1 min, the Buffer solution was aspirated away from the functionalized beads. The MHC monomer/CD80/CD58 antigen presenting beads were resuspended in 100 microliters Wash Buffer, stored at 4° C., and used without further manipulation. The 1e7 2.80 micron diameter functionalized DynaBeads have a nominal surface area of about 24e6 square microns available for contact with T lymphocyte cells, which, as described herein, does not reflect the total surface occupied by pMHC and costimulatory molecular ligands. 
     Example 21. Activation of CD8+ T Lymphocytes by Antigen Presenting Beads with Antibody Costimulation Compared to Recombinant Protein Costimulation 
     Cells: CD8+ T lymphocytes were enriched in a medium including RPMI plus 10% fetal bovine serum (FBS) from commercially available PBMCs following manufacturer&#39;s directions for EasySep™ Human CD8+ T Cell Isolation Kit, commercially available kit from StemCell Technologies Canada Inc. (Catalog #17953), by negative selection. 
     Culture medium and diluent for reagent additions: Advanced RPMI (ThermoFisher Catalog #12633020, 500 mL); lx GlutaMAX (ThermoFisher Catalog #35050079, 5 mL); 10% Human AB serum (zen-bio, Catalog # HSER-ABP 100 mL, 50 mL); and 50 nM beta-mercaptoethanol (ThermoFisher Catalog #31350010, 50 nm stock, 0.5 mL, final conc 50 micromolar). 
     Experimental Setup: For each activating species, a single 96-well tissue-culture treated plate (VWR Catalog #10062-902) was used: 
     Wellplate 1. Antigen presenting beads with antibody costimulation). 
     Wellplate 2. Antigen presenting beads with random biotinylated recombinant protein co-activation. 
     Wellplate 3. Antigen presenting beads with BirA biotinylated recombinant protein co-activation. 
     CD8+ T lymphocytes (2e5) (80-90% pure) were added to each individual well. 
     Antigen presenting surface beads (2e5), prepared by a similar preparation as described in Example 15, presenting pMHC including MART1, anti-CD28 antibody and anti-CD2 antibody, were added to each of the wells in wellplate 1. pMHC was loaded at 0.5 micrograms/1e7 beads. Anti-CD28 antibody was loaded at 1.5 micrograms/1e7 beads. Anti-CD2 antibody was loaded at 1.5 micrograms/1e7 beads. 
     Antigen presenting surface beads (2e5), prepared as in Example 20A, presenting pMHC including MART1, recombinant CD80 and recombinant CD58, were added to each of the wells in wellplate 2. pMHC was loaded at 0.5 micrograms/1e7 beads. Recombinant CD80 was loaded at 4.5 micrograms/1e7 beads. Recombinant CD58 was loaded at 1.5 micrograms/1e7 beads. 
     Antigen presenting surface beads (2e5), prepared as in Example 20B, presenting pMHC including MART1, BirA biotinylated recombinant CD80 and recombinant CD58, were added to each of the wells in wellplate 3. pMHC was loaded at 0.5 micrograms/1e7 beads. Recombinant CD80 was loaded at 1.5 micrograms/1e7 beads. Recombinant CD58 was loaded at 1.5 micrograms/1e7 beads. 
     Each wellplate was cultured at 37° C. On day 0, IL-21 (150 ng/milliliter) in CTL media, was added to each well of wellplates 1 and 2, providing a final concentration in each well of 30 ng/mL. On day 2, IL21 was added to each well of the wellplates, to a final concentration of 30 ng/mL. Culturing was continued to day 7. 
     Day 7. Restimulation. A second aliquot of antigen presenting beads with antibody costimulation or recombinant protein costimulation was delivered to each occupied well in wellplate 1, wellplate 2 and wellplate 3, respectively. IL21 was added to each well of the wellplate to a final concentration of 30 ng/mL. Culturing was continued. 
     Day 8. Addition of 50 microliters of IL-2 (50 IU/mL) and IL-7 (25 ng/mL) was made to each well in each wellplate to provide a final concentration of 10 IU/mL and 5 ng/mL respectively. Culturing was continued. 
     Day 9. Addition of 50 microliters of IL-21(150 ng/mL) was made to each occupied well of each well plate to a final concentration of 30 ng/mL. Culturing was continued. 
     Day 14. The wells from each wellplate were individually stained for MHC tetramer (Tetramer PE, MBL Catalog # T02000, 1 microliter/well), CD4 (Biolegend Catalog #300530, 0.5 microliters/well); CD8 (Biolegend Catalog #301048, 0.5 microliters/well); CD28(Biolegend Catalog #302906, 0.31 microliters/well); CD45RO (Biolegend Catalog #304210, 0.63 microliters/well); CCR7 (CD197, Biolegend Catalog #353208, 0.5 microliters/well); and viability (BD Catalog #565388, 0.125 microliters/well). Resuspend each well with 150 microliters FACS buffer and 10 microliters of Countbright™ beads (ThermoFisher Catalog # C36950). FACS analysis was performed on a FACSCelesta™ flow cytometer (BD Biosciences). 
       FIG. 19A  shows the frequency of MART1-specific T cells (% of all live cells) in each well expanded using Antigen presenting beads with Antibodies or randomly biotinylated recombinant protein ligands.  FIG. 19B  shows the number of MART1-specific T cells in each well expanded using Antigen presenting beads with Antibodies or randomly biotinylated recombinant protein ligands.  FIG. 19C  shows the frequency of MART1 T cells that express high levels of CD28, an indicator of a memory precursor phenotype comparing antibody stimulation or randomly biotinylated recombinant protein ligands. 
       FIG. 19D  shows the frequency of MART1-specific T cells (% of all live cells) in each well expanded using Antigen presenting beads with Antibodies or recombinant protein BirA ligands.  FIG. 19E  shows the number of MART1-specific T cells in each well expanded using Antigen presenting beads with Antibodies or recombinant protein BirA ligands.  FIG. 19F  shows the frequency of MART1 T cells that express high levels of CD28, an indicator of a memory precursor phenotype. It can be seen that the antigen presenting beads with recombinant protein ligands biotinylated by BirA effectively expand antigen-specific CD8+ T cells and that many of the expanded cells take on a memory precursor phenotype. In contrast, use of randomly biotinylated protein ligands did not lead to significant populations of antigen specific T cells and also did not provide cells with a memory precursor phenotype. 
     Example 22. Comparison Between Loading of and Activation with Convoluted Polymeric Beads Vs. Substantially Spherical Silica Beads 
     Example 22A. Comparison of Activating Species Loading onto Polymer and Silica Antigen Presenting Beads 
     Amounts of pMHC and costimulation antibodies that could be deposited onto Polymer and 
     Silica beads was measured. 
     Streptavidin functionalized (covalently coupled) DynaBeads™ (ThermoFisher Catalog #11205D, bead stock at 6.67e8/mL) were delivered (15 microliters; 1e7 beads) to 1.5 mL microcentrifuges tube with 1 mL of Wash Buffer (DPBS (No Magnesium +2 , No Calcium +2 , 244 mL); EDTA (1 ml, final concentration 2 mM); and BSA (5 ml of 5%, final concentration 0.1%), and separated using a magnetic DynaBead rack. The wash/separation with 1 mL of the Wash Buffer was repeated, and a further 200 microliters of Wash Buffer was added with subsequent pulse centrifugation. Supernatant Wash Buffer was removed. 
     Biotin functionalized (covalently coupled) smooth silica beads were first coated with Streptavidin by storage in 100 micromolar Streptavidin. Approximately 5e6 beads were washed by dilution into 1 milliliter of Wash Buffer in a microcentrifuge tube, followed by centrifugation at 1,000×g for 1 minute. The supernatant was carefully removed by aspiration, and the wash process repeated twice more. Supernatant Wash Buffer was removed. 
     To prepare antigen presenting beads, Wash Buffer (600 microliters) containing 0.5 micrograms biotinylated Monomer MHC (HLA-A*02:01 SLC45A2 (Biolegend, Custom Product, SLYSYFQKV) was dispensed into the tubes with the DynaBeads and Silica beads, and the beads were resuspended by pipetting up and down. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged at 1,000×g for one minute, and the supernatant liquid removed. 
     Wash Buffer (600 microliters) with 1.5 micrograms of biotinylated anti-CD28 and 1.5 micrograms of biotinylated anti-CD2 was used to resuspend each bead sample, and the beads were resuspended by pipetting up and down. The antibodies were allowed to bind for 30 min at 4 C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged at 1,000×g for one minute, and the supernatant liquid removed. Finally, the beads were resuspended in 100 microliters of Wash Buffer. 
     Two samples of approximately 2e5 Polymer antigen presenting beads or 1e5 Silica antigen presenting beads were washed with Wash Buffer (1 milliliter). The bead samples were resuspended in 100 microliters of Wash Buffer and stained by addition of 1 microliter of APC-conjugated anti-HLA-A (Biolegend, Catalog Number 343308) or 1 microliter of APC-conjugated monoclonal anti-Mouse-IgG1 (Biolegend, Catalog Number 406610). The beads were mixed with the antibody and allowed to stain for 30 minutes in the dark. After staining, beads were washed, resuspended in Wash Buffer (200 microliters) and transferred to tubes for analysis by Flow Cytometry. 
     A set of Quantum Simply Cellular fluorescence quantitation beads (Bangs Labs, Catalog Number 815) was then prepared to determine the number of anti-HLA-A antibodies and anti-Mouse IgG1 antibodies bound to each antigen presenting bead sample. The quantitation beads have antibody binding capacities determined by the manufacturer. A drop of each bead with pre-determined binding capacity was placed in microcentrifuge tubes with 50 microliters of Wash Buffer. To the tubes, 5 microliters of APC-conjugated anti-HLA-A or APC-conjugated anti-Mouse IgG1 was added and mixed by vortexing. The beads were stained for 30 minutes in the dark, washed using the same method as above. The beads with different binding capacities were then pooled into one sample and transferred to a single tube. A drop of blank beads (no antibody binding capacity) was added and the beads were analyzed by Flow Cytometry. 
     The quantitation beads were analyzed by Flow Cytometry (BD FACSCelesta, Becton Dickinson and Company) by recording 5,000 events. The quantitation beads were identified by Forward Scatter and Side Scatter, and the median intensity in the APC channel of each bead recorded. This data was recorded in a proprietary Excel spreadsheet provided by the manufacturer (Bangs) that calculates a standard curve of APC intensity versus antibody binding capacity. After verifying that the calibration was linear, the antigen presenting bead samples were analyzed. The beads were identified by Forward and Side Scatter, and the median intensity in the APC channel recorded on the spreadsheet. The spreadsheet calculates the number of APC anti-HLA-A antibodies or APC anti-Mouse IgG1 on each antigen presenting bead. Assuming that 1 anti-HLA-A antibody binds to one pMHC on the antigen presenting bead, this value represents the number of pMHC molecules on each bead. Similarly, the number of costimulation antibodies can be determined. 
     From the nominal surface area of each antigen presenting bead, the density (number of molecules/square micron of bead surface) of each species can be determined. The total number of pMHC on the Silica microspheres was determined to be approximately 800,000 pMHC/antigen presenting bead. The total number of costimulation antibodies was determined to be about 850,000 antibodies/bead. As there is no way to distinguish the anti-CD28 and anti-CD2 clones used to prepare the antigen presenting beads (they are the same isotype), it is assumed that the ratio of the two antibodies is 1:1. Due to the regularity of the Silica bead surfaces, the surface area can be reasonably modeled from a sphere. For a 4.08 micron diameter microsphere, this corresponds to a surface area of about 52.3 square microns. From this, it can be estimated that about 15,000 pMHC and 15,000 costimulation antibodies per square micron of bead surface are presented by the Silica antigen presenting beads as shown in Table 1. The distribution across each bead population for each ligand class is shown in  FIG. 20A , where each row  2010 ,  2020 , and  2030  shows the distribution of pMHC in the left hand graph, and the distribution of costimulation antibodies in the right hand graph for each type of bead. Row  2010  shows distribution of the ligands for 2.8 micron diameter convoluted polymer beads (Dynal). Row  2020  shows distribution of ligands for 4.5 micron diameter convoluted polymer beads (Dynal). Row  2030  shows distribution of ligands for a 2.5 micron diameter substantially spherical silica bead as produced in Example 10B. Tightly controlled populations of beads were produced, with the substantially spherical silica beads having even more tightly controlled distribution of ligands over the entire population, and slightly higher median distribution. Thus, the use of substantially spherical silica beads can lead to more reproducible and controllable production of these activating species. Additionally, since all of the ligands are accessible to T lymphocytes, unlike the convoluted polymer bead ligand distribution, more efficient use is made of precious biological ligands such as antibodies. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Ligand quantification and density for convoluted polymer 
               
               
                 beads and substantially spherical silica beads. 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Costimulation 
               
               
                   
                   
                 pMHC 
                   
                 Antibody 
               
               
                   
                   
                 Density 
                 Costimulation 
                 Density 
               
               
                   
                 pMHC/ 
                 (molecules/ 
                 antibodies/ 
                 (molecules/ 
               
               
                 Bead 
                 bead 
                 sq micron) 
                 bead 
                 sq micron) 
               
               
                   
               
               
                 M-280 
                 487,209 
                 19,781 
                 426,992 
                 17,336 
               
               
                 Polymer 
               
               
                 Silica 
                 807,180 
                 14,847 
                 845,388 
                 15,550 
               
               
                   
               
            
           
         
       
     
     For Polymer beads, the convoluted surface makes the relationship between bead diameter and surface area less straightforward. From the quantitation, it was determined that Polymer antigen presenting beads based on M-280 DynaBeads had about 480,000 pMHC molecules and 425,000 costimulation antibodies on their surface. For a sphere of radius 1.4 microns (equal to the nominal radius of M-280 DynaBeads, this corresponds to about 20,000 pMHC and 17,000 costimulation antibodies per square micron, as shown in Table 1. However, due to the convoluted surface of the Polymer beads, the actual surface area is likely larger, and thus the actual density lower. From  FIGS. 20E, 20F and 20G , though, it can be seen that these beads can be used as antigen presenting bead substrates to expand large numbers of antigen-specific T cells, where the expansion was performed in a similar manner as in Example 22B. In addition, from  FIG. 20H , these antigen presenting beads generated large numbers of antigen-specific T cells with high expression of CD28, indicative of a memory precursor phenotype. 
     Antigen presenting beads were prepared in the same manner using M-450 Epoxy DynaBeads modified with Streptavidin. From flow cytometry, antigen presenting beads prepared from M-450 beads had approximately the same number of pMHC and costimulation antibody molecules as antigen presenting beads prepared with M-280 DynaBeads. As the M-450 DynaBeads are larger than the M-280 beads, this implies that the density of the activating species on the M-450 antigen presenting beads was about 2-3 times lower than on M-280 antigen presenting beads. However, as can be seen from  FIG. 20F , M-450 antigen presenting beads generated positive wells (in which SLC45A2-specific T cells expanded to represent 0.5% or more of the live cells in the well) when used to expand SLC45A2 T cells. From  FIGS. 20G and 20H , it can be seen that these wells generated SLC45A2 T cells at high frequencies, and the number of SLC45A2 T cells was comparable to the number obtained from M-280 antigen presenting beads. In addition, from  FIG. 20I , the fraction of SLC45A2 T cells expressing high levels of CD28 was comparable when using M-280 or M-450 antigen presenting beads to expand SLC45A2 T cells. 
     Example 22B. Expansion of Antigen-Specific T Cells with Polymer Vs Silica Beads 
     Expansion of antigen-specific T cells using Silica antigen presenting beads was tested and compared to convoluted polymeric beads (polystyrene). 
     Streptavidin functionalized (covalently coupled, convoluted) DynaBeads™ (ThermoFisher Catalog #11205D, bead stock at 6.67e8/mL) were delivered (15 microliters; 1e7 beads) to 1.5 mL microcentrifuges tube with 1 mL of Wash Buffer (DPBS (No Magnesium +2 , No Calcium +2 , 244 mL); EDTA (1 ml, final concentration 2 mM); and BSA (5 ml of 5%, final concentration 0.1%), and separated using a magnetic DynaBead rack. The wash/separation with 1 mL of the Wash Buffer was repeated, and a further 200 microliters of Wash Buffer was added with subsequent pulse centrifugation. Supernatant Wash Buffer was removed. 
     Biotin functionalized (covalently coupled) smooth silica beads, prepared as in Example 10B, were first coated with Streptavidin by storage in 100 micromolar Streptavidin. Approximately 5e6 beads were washed by dilution into 1 milliliter of Wash Buffer in a microcentrifuge tube, followed by centrifugation at 1,000×g for 1 minute. The supernatant was carefully removed by aspiration, and the wash process repeated twice more. Supernatant Wash Buffer was removed. 
     To prepare antigen presenting beads, Wash Buffer (600 microliters) containing 0.5 micrograms biotinylated Monomer MHC (HLA-A*02:01 SLC45A2 (Biolegend, Custom Product, SLYSYFQKV) was dispensed into the tubes with the DynaBeads and Silica beads, and the beads were resuspended by pipetting up and down. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged at 1,000×g for one minute, and the supernatant liquid removed. 
     Wash Buffer (600 microliters) with 1.5 micrograms of biotinylated anti-CD28 and 1.5 micrograms of biotinylated anti-CD2 was used to resuspend each bead sample, and the beads were resuspended by pipetting up and down. The antibodies were allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged at 1,000×g for one minute, and the supernatant liquid removed. Finally, the beads were resuspended in 100 microliters of Wash Buffer. 
     Cells: CD8+ T lymphocytes were enriched in a medium including RPMI plus 10% fetal bovine serum (FBS) from commercially available PBMCs following manufacturer&#39;s directions for EasySep™ Human CD8+ T Cell Isolation Kit, commercially available kit from StemCell Technologies Canada Inc. (Catalog #17953), by negative selection. 
     Culture medium and diluent for reagent additions: Advanced RPMI (ThermoFisher Catalog #12633020, 500 mL); lx GlutaMAX (ThermoFisher Catalog #35050079, 5 mL); 10% Human AB serum (zen-bio, Catalog # HSER-ABP 100 mL, 50 mL); and 50 nM beta-mercaptoethanol (ThermoFisher Catalog #31350010, 50 nm stock, 0.5 mL, final conc 50 micromolar). 
     Experimental Setup: For each type of antigen presenting bead (Silica or Polymer, as prepared above in this example), a single 96 tissue-culture treated wellplate (VWR Catalog #10062-902) was used. Silica antigen presenting beads were mixed with CD8+ T lymphocytes at ˜1:2 beads:cell. CD8+ T lymphocytes (2e5) (80-90% pure) were added to each well with approximately 1e5 antigen presenting beads (wellplate 1). Polymer antigen presenting beads were mixed with CD8+ T lymphocytes at ˜1:1 beads:cell. CD8+ T lymphocytes (2e5) (80-90% pure) were added to each well with approximately 2e5 antigen presenting beads (wellplate 2). 
     Each wellplate was cultured at 37° C. On day 0, IL-21 (150 ng/milliliter) in CTL media, was added to each well of wellplates 1 and 2, providing a final concentration in each well of 30 ng/mL. On day 2, IL21 was added to each well of the wellplates, to a final concentration of 30 ng/mL. Culturing was continued to day 7. 
     Day 7. Restimulation. A second aliquot of antigen presenting beads was added to the corresponding wells in wellplate 1 and wellplate 2. For the Silica beads, approximately 1e5 beads (Silica beads as prepared above in this example) were added. For the Polymer beads, approximately 2e5 beads (convoluted polymer beads as prepared above in this example) were added. IL21 was added to each well of the wellplate to a final concentration of 30 ng/mL. Culturing was continued. 
     Day 8. Addition of 50 microliters of IL-2 (50 IU/mL) and IL-7 (25 ng/mL) was made to each well in wellplate 1 and wellplate 2 to provide a final concentration of 10 IU/mL and 5 ng/mL respectively. Culturing was continued. 
     Day 9. Addition of 50 microliters of IL-21(150 ng/mL) was made to each occupied well of wellplate 1 and wellplate 2 to a final concentration of 30 ng/mL. Culturing was continued. 
     Day 14. The wells from each wellplate were individually stained for MHC tetramer (Tetramer PE, MBL Catalog # T02000, 1 microliter/well), CD4 (Biolegend Catalog #300530, 0.5 microliters/well); CD8 (Biolegend Catalog #301048, 0.5 microliters/well); CD28(Biolegend Catalog #302906, 0.31 microliters/well); CD45RO (Biolegend Catalog #304210, 0.63 microliters/well); CCR7 (CD197, Biolegend Catalog #353208, 0.5 microliters/well); and viability (BD Catalog #565388, 0.125 microliters/well). Each well was resuspended with 150 microliters FACS buffer and 10 microliters of Countbright™ beads (ThermoFisher Catalog # C36950). FACS analysis was performed on a FACSCelesta™ flow cytometer (BD Biosciences). 
       FIG. 20B  shows the percentage of positive wells (in which SLC45A2-specific T cells expanded to represent 0.5% or more of the live cells in the well) after expansion using the Polymer or Silica antigen presenting beads.  FIG. 20C  shows SLC45A2 T cell frequency (% of live cells in each well) after expansion with the Polymer or Silica antigen presenting beads.  FIG. 20D  shows the total number of SLC454A2 T cells in each of the wells.  FIG. 20E  shows the percentage of SLC45A2 T cells in the wells that expressed high levels of CD28, indicating the potential for differentiation into a memory T cell. From these plots, it can be seen that the Silica antigen presenting beads generate positive wells, and that the Silica antigen presenting beads expand SLC45A2 T cells as well or better than Polymer antigen presenting beads. In addition, the Silica antigen presenting beads produce cells with high expression of CD28, indicating that they support formation of memory precursor T cells, a desired phenotype for the cellular product. 
     For Polymer beads, the convoluted surface makes the relationship between bead diameter and surface area less straightforward. From the quantitation, it was determined that Polymer antigen presenting beads based on M-280 DynaBeads had about 480,000 pMHC molecules and 425,000 costimulation antibodies on their surface. For a sphere of radius 1.4 microns (equal to the nominal radius of M-280 DynaBeads, this corresponds to about 20,000 pMHC and 17,000 costimulation antibodies per square micron. However, due to the convoluted surface of the Polymer beads, the actual surface area is likely larger, and thus the actual density lower. However, from  FIGS. 20F, 20G and 20H , it can be seen that these beads can be used as antigen presenting bead substrates to expand large numbers of antigen-specific T cells. In addition, from  FIG. 20I , these antigen presenting beads generate large numbers of antigen-specific T cells with high expression of CD28, indicative of a memory precursor phenotype. 
     Example 23A. Preparation of Antigen Presenting Beads with Defined Ligand Densities 
     Example 23A.1. Preparation of Streptavidin Presenting Beads 
     Three-fold serial dilutions of pMHC (HLA-A*02:01 SLC45A2 (Biolegend, Custom Product, SLYSYFQKV) in Wash Buffer were prepared. 20 microliters of Wash Buffer was added to a microcentrifuge tube for each serial dilution to be performed. Into the first serial dilution tube, 10 microliters of the pMHC were added. The diluted pMHC was mixed by vortexing. 10 uL of the diluted pMHC mixture was then used to prepare the subsequent serial dilution for a total of seven dilutions. 
     To determine the relationship between concentration of pMHC in solution and the density (molecules/unit area) deposited on the beads, Biotin functionalized (covalently coupled) smooth (e.g., substantially spherical as described above) 4 micron monodisperse silica beads (Cat. # SiO2MS-1.8 4.08 um-1 g, Cospheric), prepared as in Example 10B, were first coated with Streptavidin by storage in 100 micromolar Streptavidin. Approximately 1e7 beads were washed by dilution into 1 milliliter of Wash Buffer in a microcentrifuge tube, followed by centrifugation at 1,000×g for 1 minute. The supernatant was carefully removed by aspiration, and the wash process repeated twice more. After washing, approximately 1e6 beads were delivered into eight microcentrifuge tubes, centrifuged again, and the supernatant carefully removed. 
     Example 23A.2. Preparation of Beads Having a Range of MHC Concentration 
     Wash Buffer (120 microliters) containing 4.5 micrograms biotinylated Monomer MHC (HLA-A*02:01 SLC45A2 (Biolegend, Custom Product, SLYSYFQKV) was dispensed into one of the microcentrifuge tubes, and the beads were resuspended by pipetting up and down. The undiluted pMHC and serial dilutions of pMHC were further diluted into Wash Buffer (120 microliters) and used to resuspend beads, resulting in beads suspended in solutions with 4.5, 1.5, 0.5, 0.167, 0.056, 0.019, 0.006, or 0.002 micrograms of pMHC monomer per 5e6 beads. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged, the supernatant liquid removed, and the beads resuspended at approximately 5e7/milliliter. 
     Approximately 1e5 beads prepared with each concentration of pMHC were washed with Wash Buffer (1 milliliter). The bead samples were resuspended in 100 microliters of Wash Buffer and stained by addition of 1 microliter of APC-conjugated anti-HLA-A (Biolegend, Catalog Number 343308). The beads were mixed with the antibody and allowed to stain for 30 minutes in the dark. After staining, beads were washed, resuspended in Wash Buffer (200 microliters) and transferred to tubes for analysis by Flow Cytometry. 
     A set of Quantum Simply Cellular fluorescence quantitation beads (Bangs Labs, Catalog Number 815) was then prepared to determine the number of anti-HLA-A antibodies bound to each antigen presenting bead sample. The quantitation beads have antibody binding capacities determined by the manufacturer. A drop of each bead with pre-determined binding capacity was placed in a microcentrifuge tube with 50 microliters of Wash Buffer. To the tube, 5 microliters of APC-conjugated anti-HLA-A was added and mixed by vortexing. The beads were stained for 30 minutes in the dark, washed using the same method as above. The beads with different binding capacities were then pooled into one sample and transferred to a single tube. A drop of blank beads (no antibody binding capacity) was added and the beads were analyzed by Flow Cytometry. 
     The quantitation beads were analyzed by Flow Cytometry (BD FACSCelesta, Becton Dickinson and Company) by recording 5,000 events. The quantitation beads were identified by Forward Scatter and Side Scatter, and the median intensity in the APC channel of each bead recorded. Quantitation was calculated as described in Example 22A, using the proprietary methodology provided by the quantitation bead manufacturer. From the antigen presenting bead standard, it is then possible to determine the concentration of pMHC in solution with beads that generates antigen presenting beads with a targeted density of pMHC, e.g., beads with approximately 10,000, 1,000, or 100 pMHC molecules per square micron, as seen in  FIG. 21A . 
     Example 23A.3. Costimulation Molecule Concentration Variation 
     Three-fold serial dilutions of biotinylated anti-CD28 and anti-CD2 in Wash Buffer were prepared. 20 microliters of anti-CD28 was mixed with 20 microliters of anti-CD2 in a microcentrifuge tube. Wash Buffer (20 microliters) was then added to a microcentrifuge tube for each serial dilution. The anti-CD28/anti-CD2 mixture (10 microliters) was then added to the first serial dilution tube. The solution was mixed using a vortexer, and 10 uL of the diluted anti-CD28/anti-CD2 mixture was then used to prepare the subsequent serial dilution for a total of seven dilutions. 
     To quantify the relationship between costimulation antibody in solution and the density (molecules/unit area) deposited on the beads, approximately 1e7 substantially spherical 4 micron silica beads, prepared as in Example 23A.1, having streptavidin binding moieties, were first washed by dilution into 1 milliliter of Wash Buffer in a microcentrifuge tube, followed by centrifugation at 1,000×g for 1 minute. The supernatant was carefully removed by aspiration, and the wash process repeated twice more. After washing, approximately 1e6 beads were delivered into eight microcentrifuge tubes, centrifuged again, and the supernatant carefully removed. 
     The beads were first functionalized with 1.0 micrograms of pMHC in Wash Buffer (1,200 microliters). After washing, the beads were resuspended in Wash Buffer (1,000 microliters). Into eight microcentrifuge tubes, 100 microliters of pMHC functionalized beads was dispended. The beads were centrifuged, and the supernatant carefully removed. 
     The undiluted mixed anti-CD28 and anti-CD2 and serial dilutions of anti-CD28/anti-CD2 were further diluted into Wash Buffer (120 microliters) and used to resuspend the beads, resulting in beads suspended in solutions with 4.5, 1.5, 0.5, 0.167, 0.056, 0.019, 0.006, or 0.002 micrograms of mixed costimulation antibodies monomer per 5e6 beads. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged, the supernatant liquid removed, and the beads resuspended at approximately 5e7/milliliter. 
     Approximately 1e5 beads prepared with each concentration of costimulation antibodies was washed with Wash Buffer (1 milliliter). The bead samples were resuspended in 100 microliters of Wash Buffer and stained by addition of 1 microliter of APC-conjugated monoclonal anti-Mouse-IgG1 (Biolegend, Catalog Number 406610). The beads were mixed with the antibody and allowed to stain for 30 minutes in the dark. After staining, beads were washed, resuspended in Wash Buffer (200 microliters) and transferred to tubes for analysis by Flow Cytometry. 
     A set of Quantum Simply Cellular fluorescence quantitation beads (Bangs Labs, Catalog Number 815) was then prepared to determine the number of APC anti-Mouse IgG1 antibodies bound to each antigen presenting bead sample. A drop of each bead with pre-determined binding capacity was placed in a microcentrifuge tube with 50 microliters of Wash Buffer. To the tube, 5 microliters of APC-conjugated anti-Mouse IgG1 was added and mixed by vortexing. The beads were stained for 30 minutes in the dark, washed using the same method as above. The beads with different binding capacities were then pooled into one sample and transferred to a single tube. A drop of blank beads (no antibody binding capacity) was added and the beads were analyzed by Flow Cytometry. 
     The quantitation beads were analyzed by Flow Cytometry (BD FACSCelesta, Becton Dickinson and Company) by recording 5,000 events. The quantitation beads were identified by Forward Scatter and Side Scatter, and the median intensity in the APC channel of each bead recorded. Quantitation was performed as described in Example 22A, using proprietary methods provided by the quantitation bead manufacturer. This quantitation method calculates the number of APC anti-Mouse IgG1 antibodies on each antigen presenting bead. Assuming that 1 anti-Mouse IgG1 antibody binds to one costimulation antibody on the antigen presenting bead, this value represents the number of costimulation antibodies on each bead. From the antigen presenting bead standards, it is then possible to determine the concentration of costimulation antibodies in solution with beads that generates antigen presenting beads with a targeted density of costimulation antibodies, e.g., beads with approximately 10,000, 1,000, or 100 costimulation molecules per square micron, as seen in  FIG. 21B . 
     Example 23B. Expansion of Antigen-Specific T Cells with Antigen Presenting Beads with Different Ligand Densities 
     Using the plots of pMHC and costimulation antibody concentration versus density on the resulting antigen presenting beads ( FIG. 21A ), it was determined what concentration of each pMHC should be used to prepare antigen presenting beads with ˜10,000, ˜1,000 or ˜100 pMHC per square micron of bead surface. This process was repeated to determine the concentration of anti-CD28 and anti-CD2 to be used to prepare antigen presenting beads with ˜10,000, ˜1,000 or ˜100 costimulation antibodies per square micron of bead surface. 
     Example 23B.1 
     Biotin functionalized (covalently coupled) smooth silica beads, prepared as in Example 23.A.1 were first coated with Streptavidin by storage in 100 micromolar Streptavidin. Approximately 5e7 beads were washed by dilution into 1 milliliter of Wash Buffer in a microcentrifuge tube, followed by centrifugation at 1,000×g for 1 minute. The supernatant was carefully removed by aspiration, and the wash process repeated twice more. After washing, approximately 5e6 beads were delivered into three microcentrifuge tubes, centrifuged again, and the supernatant carefully removed. 
     Example 23B.2 
     To prepare antigen presenting beads with titrated pMHC, Wash Buffer (600 microliters) containing 0.5, 0.056, or 0.006 micrograms biotinylated Monomer MHC (HLA-A*02:01 MART-1 (MBL International Corp., Catalog No. MR01008, ELAGIGILTV) was dispensed into three microcentrifuge tubes, and the beads were resuspended by pipetting up and down. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged at 1,000×g for one minute, and the supernatant liquid removed. 
     Wash Buffer (600 microliters) with 1.0 microgram of mixed biotinylated anti-CD28 and biotinylated anti-CD2 was used to resuspend each bead sample, and the beads were resuspended by pipetting up and down. The antibodies were allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged at 1,000×g for one minute, and the supernatant liquid removed. Finally, the beads were resuspended in 100 microliters of Wash Buffer. The loading of the beads with the desired order of magnitude of pMHC and antibodies was verified by Flow Cytometry analysis and comparison to quantitation beads. 
     Wash Buffer (600 microliters) with 1.0 micrograms of anti-CD28 and anti-CD2 was used to resuspend each bead sample, and the beads were resuspended by pipetting up and down. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged at 1,000×g for one minute, and the supernatant liquid removed. Finally, the beads were resuspended in 100 microliters of Wash Buffer. The loading of the beads with the desired order of magnitude of pMHC was verified by Flow Cytometry analysis and comparison to quantitation beads. 
     Example 23B.3 
     To prepare antigen presenting beads with titrated costimulation antibodies, Wash Buffer (1,200 microliters) containing 1.5 micrograms biotinylated Monomer MHC (HLA-A*02:01 MART-1 (MBL International Corp., Catalog No. MR01008, ELAGIGILTV) was dispensed into a microcentrifuge tube containing 1.5e7 washed beads from Example 23.111, and the beads were resuspended by pipetting up and down. The monomer was allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged at 1,000×g for one minute, and the supernatant liquid removed. 
     The beads were then resuspended in Wash Buffer (900 microliters), and 300 microliters of the beads transferred to 3 microcentrifuge tubes. 
     Wash Buffer (300 microliters) with 1.0 microgram of mixed anti-CD28 and anti-CD2, 0.111 micrograms of mixed antiCD28 and anti-CD2, or 0.012 micrograms of mixed anti-CD28 and anti-CD2 was mixed into the three bead samples, and the beads were thoroughly mixed by pipetting up and down. The antibodies were allowed to bind for 30 min at 4° C. After 15 minutes, the mixtures were pipetted up and down again. The tubes were centrifuged at 1,000×g for one minute, and the supernatant liquid removed. Finally, the beads were resuspended in 100 microliters of Wash Buffer. The loading of the beads with the desired order of magnitude of costimulation antibodies was verified by Flow Cytometry analysis and comparison to quantitation beads. 
     Example 23B.4 
     Stimulation. Cells: CD8+ T lymphocytes were enriched in a medium including RPMI plus 10% fetal bovine serum (FBS) from commercially available PBMCs following manufacturers directions for EasySep™ Human CD8+ T Cell Isolation Kit, commercially available kit from StemCell Technologies Canada Inc. (Catalog #17953), by negative selection. 
     Culture medium and diluent for reagent additions: Advanced RPMI (ThermoFisher Catalog #12633020, 500 mL); 1× GlutaMAX (ThermoFisher Catalog #35050079, 5 mL); 10% Human AB serum (zen-bio, Catalog # HSER-ABP 100 mL, 50 mL); and 50 nM beta-mercaptoethanol (ThermoFisher Catalog #31350010, 50 nm stock, 0.5 mL, final conc 50 micromolar). 
     Experimental Setup: For each activation species titration (pMHC or costimulation antibodies), a single 96 tissue-culture treated wellplate (VWR Catalog #10062-902) was used. Antigen presenting beads with ˜10,000, ˜1,000 or ˜100 pMHC per square micron of bead surface and with ˜10,000 costimulation antibodies per square micron of bead surface (from Example 23.6.2) were mixed with CD8+ T lymphocytes at ˜1:2 beads:cell. CD8+ T lymphocytes (2e5) (80-90% pure) were added to each well with approximately 1e5 antigen presenting beads (wellplate 1). Antigen presenting beads with ˜10,000 pMHC per square micron of bead surface and with ˜10,000, ˜1,000 or ˜100 costimulation antibodies per square micron of bead surface (from Example 23.6.3) were mixed with CD8+ T lymphocytes at ˜1:2 beads:cell. CD8+ T lymphocytes (2e5) (80-90% pure) were added to each well with approximately 1e5 antigen presenting beads (wellplate 2). 
     Each wellplate was cultured at 37° C. On day 0, IL-21 (150 ng/milliliter) in CTL media, was added to each well of wellplates 1 and 2, providing a final concentration in each well of 30 ng/mL. On day 2, IL21 was added to each well of the wellplates, to a final concentration of 30 ng/mL. Culturing was continued to day 7. 
     Day 7. Restimulation. A second aliquot of antigen presenting beads with the targets density of pMHC or costimulation antibody was added to the corresponding wells in wellplate 1 and wellplate 2. IL21 was added to each well of the wellplate to a final concentration of 30 ng/mL. Culturing was continued. 
     Day 8. Addition of 50 microliters of IL-2 (50 IU/mL) and IL-7 (25 ng/mL) was made to each well in wellplate 1 and wellplate 2 to provide a final concentration of 10 IU/mL and 5 ng/mL respectively. Culturing was continued. 
     Day 9. Addition of 50 microliters of IL-21(150 ng/mL) was made to each occupied well of wellplate 1 and wellplate 2 to a final concentration of 30 ng/mL. Culturing was continued. 
     Day 14. The wells from each wellplate were individually stained for MHC tetramer (Tetramer PE, MBL Catalog # T02000, 1 microliter/well), CD4 (Biolegend Catalog #300530, 0.5 microliters/well); CD8 (Biolegend Catalog #301048, 0.5 microliters/well); CD28 (Biolegend Catalog #302906, 0.31 microliters/well); CD45RO (Biolegend Catalog #304210, 0.63 microliters/well); CCR7 (CD197, Biolegend Catalog #353208, 0.5 microliters/well); and viability (BD Catalog #565388, 0.125 microliters/well). Each well was resuspended with 150 microliters FACS buffer and 10 microliters of Countbright™ beads (ThermoFisher Catalog # C36950). FACS analysis was performed on a FACSCelesta™ flow cytometer (BD Biosciences).  FIG. 21C  shows the number of MART1-specific T cells in each well expanded using antigen presenting beads with various densities of pMHC/square micron.  FIG. 21D  shows the expression level of CD127, a marker of memory precursor T cells, on the MART1-specific T cells from  FIG. 21C . From these plots, it can be seen that the number of MART1-specific T cells and the expression of CD127 on these cells is insensitive to pMHC density when the density is ˜100 pMHC/square micron or higher. 
       FIG. 21E  shows the number of MART1-specific T cells in each well expanded using antigen presenting beads with various densities of costimulation antibodies/square micron.  FIG. 21F  shows the expression level of CD127, a marker of memory precursor T cells, on the MART1-specific T cells from  FIG. 21E . From these plots, it can be seen that the number of MART1-specific T cells and the expression of CD127 on these cells is sensitive to costimulation antibody density. Beads prepared with ˜10,000 costimulation antibodies per square micron, which nearly saturated the biotin binding sites of the bead (see  FIG. 21B ), generated the highest number of antigen-specific T cells, and those cells expressed the highest levels of CD127. As the number of costimulatory ligands was decreased to the lower end of the loading regime, primary stimulation by the pMHC was not as effectively co-stimulated, and the phenotype of the cell product is affected. 
     Example 24. Performance of an Antigen-Specific Cytotoxicity Assay within a Microfluidic Device 
     Experimental Design: Tumor cell lines obtained from melanoma cells, including Mel 526 cells and A375 cells, were tested in an on-chip T cell killing assay. Each cell line was grown up in vitro according to standard procedures, then labeled with CellTrace™ Far Red dye (Cat. #034572, ThermoFisher Scientific), which provides stable intracellular labelling. Each population of labeled tumor cells were flowed into an individual microfluidic chip (Berkeley Lights, Inc.) in T cell media (Adv. RPMI+10% Human AB serum (Cat. #35-060-Cl, Corning)+Gln+50 uM 2-mercaptoethanol (BME, Cat. #31350-010, Gibco, ThermoFisher Scientific) supplemented with 10 uM fluorogenic Caspase-3 substrate (DEVD, Green) (Nucview® 488, Cat. #10403, Biotium). Groups of labeled tumor cells (˜2-10) were loaded into each of a plurality of sequestration pens on each of the two microfluidic chips (one for Mel 526 cells, and one for A375 cells) by tilting the microfluidic chip and allowing gravity to pull the tumor cells into the sequestration pens, providing a final concentration of the Caspase-3 substrate at 5 uM at Time=0 for the assay for each microfluidic chip. The Caspase-3 substrate provides no fluorescent signal until cleaved, so at Time=0, there was no fluorescent signal due to this reagent. T cells expanded against the SLC45A2 antigen, according to an endogenous T cell (ETC) protocol as described above, were flowed into each of the two microfluidic chips and gravity loaded on top of the tumor cells of each respective chip. Typically, after loading the tumor cells and T cells, each sequestration pen contained 0-5 tumor cells per T cell. As shown in the brightfield image (BF) for each time point and for each microfluidic chip containing SLC45A2-specific T cells and Mel526 tumor cells ( FIG. 22A ) and SLC45A2-specific T cells and A375 cells ( FIG. 22B ), respectively, populations of the cells are present. T cell media (Adv. RPMI+10% Human AB serum+Gln+50 uM BME) supplemented with 5 uM Caspase-3 substrate (Green) (Nucview 488 from Biotium) was perfused through the microfluidic channels on each microfluidic chip and images of the sequestration pens were taken every 30 minutes (starting from the end of the T cell loading) for a period of 7 hours. The CellTrace Far Red label and cleaved, now fluorescent Caspase-3 label were visualized using different fluorescent cubes (Cy5, FITC respectively). The Mel526 melanoma cell line expresses the SLC45A2 tumor-associated antigen and was expected to be targeted and killed by the SLC45A2-specific T cells. The A375 melanoma cell line does not express the SLC45A2 tumor-associated antigen and was not expected to be targeted or killed by the SLC45A2-specific T cells, and thus was used as a negative control for T cell cytotoxicity. 
     Results: 
     Mel526 tumor cells ( FIG. 22A ) and A375 tumor cells ( FIG. 22B ) exhibited the CellTrace Far Red signal (Cy5 fluorescent cube) but no signal associated with cleavage of the Caspase-3 substrate (Green fluorescent signal, FITC fluorescent cube) at the 1 hour time point. As time progresses, the green fluorescent signal associated with cleavage of the Caspase-3 substrate increased in the Mel526 tumor cells ( FIG. 22A , up to 7 hr. time points shown) but not in the A375 tumor cells ( FIG. 22B , up to 7 hrs. time point shown). The results indicate that the Mel526 tumor cells were efficiently killed by the SLC45A2-specific T cells, with 6 of 8 sequestration pens that contain Mel526 tumor cells in  FIG. 22A  showing high levels of Caspase-3 substrate cleavage.  FIG. 22C  showed quantification of the extent of antigen-specific Mel526 tumor cell killing vs the extent of cell killing of A375 non-targeted cells over the course of the experiment. A very low amount of SLC45A2-specific T cell (fractional) killing was observed for A375 non-targeted cells, whereas the targeted antigen-specific cell killing of the Mel 526 tumor cells by the SLC45A2-specific T cells approached a 0.25 fractional killing over the same 7 hr. time period. The exposure times for each of the fluorescent images was the same for each microfluidic chip and for each time point. The decrease seen over time of the Cy5 signal from the Cell Trace Far Red stain is often observed for any set of cells; observation of such decrease for each cell type was not unexpected. 
     Example 25. Rapid Expansion of Antigen-Specific T Lymphocytes after Bead Stimulation and Characterization of Cellular Product 
     Typically after completion of antigen specific T lymphocyte activation as described in the preceding experiments, the antigen specific enriched T cells were sorted by FACS on an FACSAria Fusion System (Becton Dickinson, San Jose, Calif.) after staining 30 min RT in FACS buffer (1×DPBS w/o Ca 2+ Mg 2+  (Cat. #4190250, ThermoFisher), 5 mM EDTA (Cat. # AM9260G, ThermoFisher), 10 mM HEPES (Cat. #15630080, ThermoFisher), 2% FBS) with anti-CD8-PerCPCy5.5 (Clone RPA-T8, 301032, Biolegend, San Diego, Calif.), Tetramer-PE (MBL International, Woburn, Mass.) specific to the antigen, and Zombie NIR (Cat. #423106, Biolegend, San Diego, Calif.) to exclude dead cells. Desired cells were purity sorted by gating: size, singles, live, CD8 positive, and Tetramer positive into CTL media (Advanced RPMI (Cat. #12633020, ThermoFisher), 1× Glutamax (Cat. #35050079, ThermoFisher), 10% Human Serum (Cat. # MT35060Cl, ThermoFisher), 50 uM b-Mercaptoethanol (Cat. #31350010, ThermoFisher) with 2 mM HEPES. 
     The sorted antigen-specific T cells were then expanded in at least one round of Rapid Expansion Protocol (REP), as described in Riddell, U.S. Pat. No. 5,827,642. Lymphoblastoid Cell Line cells (LCL, the LCL cell line was a gift from Cassian Yee, M. D. Anderson Cancer Center) were irradiated with 100 Gy and PBMC from 3 donors were irradiated with 50 Gy using an X-ray irradiator. Irradiated cells were washed in RPMI containing 10% FBS and mixed in a ratio of 1:5 (LCL:PBMC). These irradiated cells were added to either FACS-sorted T cells (for a first cycle of REP), or to the product of a first cycle of REP in 200 to 500-fold excess. Cultures were set up in T cell media (Advanced RPMI, 10% Human AB Serum, GlutaMax, 50 uM b-mercaptoethanol) supplemented with 50 U/mL IL-2 (Cat. #202-IL, R&amp;D Systems) and 30 ng/mL anti-CD3 antibody (Cat. #16-0037-85, ThermoFisher). Cells were fed with fresh IL-2 on days 2, 5 and 10, and expanded according to their growth rates. 
     Expansion is typically 1,000-fold during a first REP cycle. Expansion during REP1 varied highly (316-7,800-fold, data not shown). Inaccurate quantification of low input cell numbers may have contributed to this variability. Shown here in  FIG. 23A  is fold-expansion obtained from a second REP protocol following the first cycle (n=20 experiments, 11 donors, 12 STIMs). Expansion ranged from about 200 up to about 2000 fold. However, there was no clear correlation between extent of expansion in REP1 and REP2 for a particular cell population in these experiments. 
     In  FIG. 23B , the percentages of antigen-specific T cells in the REP populations are shown for the 20 experiments of the REP protocol. What was observed was that high percentages of antigen-specific T cells (% Ag+), typically ˜90%, were maintained during at least two REP cycles. In contrast, Low % Ag+ after REP1 led to low % Ag+ after REP2. 
     In  FIG. 23C , the percentages of antigen-specific T cells also expressing co-stimulatory receptors CD27 and CD28, after the completion of REP2, are shown. In  FIG. 23D , the percentages of antigen-specific T cells also expressing CD127, a marker for a central memory phenotype which can presage persistence in vivo, after the completion of REP2 is shown. While the distribution of expression of any of the markers was not tightly clustered, and some of the individual experiments showed low (e.g., a few percent) of cells that express the desired markers, the cellular products obtained in each of these experiments demonstrated sufficiently positive phenotype across all categories to render them candidates for in-vivo introduction. Some of the depressed values seen, such as expression of CD28, may be due to the extensive stimulation using CD28 ligands used during the activation cycles, leading to depressed expression of these surface markers. 
     In  FIG. 23E , the results of antigen-specific cytotoxicity assay for each of three individual cellular populations, after two rounds of REP, are shown. The assay was performed as described in Example 24, using Mel526 cells as the Target cancer cell line and A375 cells as the non-targeted cell line, wherein the antigen specific T cells were SLC45A2-specific T cells. In each experiment, more than 50% of the targeted Mel526 cells exhibited Caspase 3 triggered fluorescent signal, while none to a few percent of the A375 non-targeted cells exhibited apoptotic behavior as signaled by the fluorogenic cleavage product of the Caspase-3 substrate. Therefore, the activated T cells still exhibited antigen-specific cell killing behavior after all of the rounds of activation and expansion. 
     Therefore, the processes of activation via antigen presentation on a synthetic surface as described herein can provide well controlled, reproducible and characterizable cellular products suitable for use in immunotherapy. The antigen-presenting surfaces described herein provide lower cost of manufacture for these individualized therapies compared to currently available experimental processes. 
     Recitation of Some Embodiments of the Disclosure. 
     1. An antigen-presenting surface for activating a T lymphocyte (T cell), including:
 
a plurality of primary activating molecular ligands, wherein each primary activating molecular ligand includes a major histocompatibility complex (MHC) Class I molecule configured to bind to a T cell receptor (TCR) of the T cell; and
 
a plurality of co-activating molecular ligands each including a TCR co-activating molecule or an adjunct TCR activating molecule, wherein each of the plurality of primary activating molecular ligands and the plurality of co-activating molecular ligands is specifically bound to the antigen presenting surface.
 
2. The antigen-presenting surface of embodiment 1, wherein the plurality of co-activating molecular ligands comprises TCR co-activating molecules and adjunct TCR activating molecules.
 
3. The antigen-presenting surface of embodiment 1 or 2, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 100:1 to about 1:100.
 
4. The antigen-presenting surface of embodiment 1 or 2, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is 100:1 to 90:1, 90:1 to 80:1, 80:1 to 70:1, 70:1 to 60:1, 60:1 to 50:1, 50:1 to 40:1, 40:1 to 30:1, 30:1 to 20:1, 20:1 to 10:1, 10:1 to 1:1, 1:1 to 1:10, 1:10 to 1:20, 1:20 to 1:30, 1:30 to 1:40, 1:40 to 1:50, 1:50 to 1:60, 1:60 to 1:70, 1:70 to 1:80, 1:80 to 1:90, or 1:90 to 1:100, wherein each of the foregoing values is modified by “about.”
 
5. The antigen-presenting surface of embodiment 1 or 2, wherein the ratio of the TCR co-activating molecules to the adjunct TCR activating molecule is about 10:1 to about 1:20.
 
6. The antigen-presenting surface of embodiment 1 or 2, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 10:1 to about 1:10.
 
7. The antigen-presenting surface of any one of the preceding embodiments, wherein the plurality of primary activating molecular ligands is disposed upon at least a portion of the antigen-presenting surface at a density from about 4×10 2  to about 3×10 4  molecules per square micron, in each portion or sub-region where it is attached.
 
8. The antigen-presenting surface of embodiment 7, wherein the plurality of primary activating molecular ligands is disposed upon at least a portion of the antigen-presenting surface at a density from about 4×10 2  to about 2×10 3  molecules per square micron.
 
9. The antigen-presenting surface of embodiment 7, wherein the plurality of primary activating molecular ligands is disposed upon at least a portion of the antigen-presenting surface at a density from about 2×10 3  to about 5×10 3  molecules per square micron.
 
10. The antigen-presenting surface of embodiment 7, wherein the plurality of primary activating molecular ligands is disposed upon at least a portion of a surface of the antigen-presenting surface at a density from about 5×10 3  to about 2×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  molecules per square micron, or about 1.25×10 4  to about 1.75×10 4  molecules per square micron.
 
11. The antigen-presenting surface of any one of embodiments 7-10, wherein the plurality of primary activating molecular ligands is disposed upon substantially all of the antigen-presenting surface at the stated density.
 
12. The antigen-presenting surface of any one of embodiments 1-11, further including a plurality of surface-blocking molecular ligands.
 
13. The antigen-presenting surface of any one of embodiments 1-12, wherein the adjunct TCR activating molecule is configured to provide adhesion stimulation.
 
14. The antigen-presenting surface of any one of embodiments 1-13, wherein the plurality of co-activating molecular ligands is disposed upon at least a portion the antigen-presenting surface at a density from about 5×10 2  to about 2×10 4  molecules per square micron or about 5×10 2  to about 1.5×10 4  molecules per square micron.
 
15. The antigen-presenting surface of any one of embodiments 1 to 14, wherein the plurality of co-activating molecular ligands is disposed upon at least a portion of the antigen-presenting surface at a density from about 5×10 3  to about 2×10 4  molecules per square micron, about 5×10 3  to about 1.5×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  molecules per square micron, about 1×10 4  to about 1.5×10 4  molecules per square micron, about 1.25×10 4  to about 1.75×10 4  molecules per square micron, or about 1.25×10 4  to about 1.5×10 4  molecules per square micron.
 
16. The antigen-presenting surface of any one of embodiments 1-14, wherein the plurality of co-activating molecular ligands is disposed upon at least a portion of the antigen-presenting surface at a density from about 2×10 3  to about 5×10 3  molecules per square micron.
 
17. The antigen-presenting surface of any one of embodiments 1-14, wherein the plurality of co-activating molecular ligands is disposed upon at least a portion of a surface of the antigen-presenting surface at a density from about 5×10 2  to about 2×10 3  molecules per square micron.
 
18. The antigen-presenting surface of any one of embodiments 14-17, wherein the plurality of co-activating molecular ligands is disposed upon substantially all of the antigen-presenting surface at the stated density.
 
19. The antigen-presenting surface of any one of embodiments 1-18, wherein a ratio of the primary activating molecular ligands to the co-activating molecular ligands present on the antigen-presenting surface is about 1:10 to about 2:1, about 1:5 to about 2:1, about 1:2 to about 2:1, about 1:10 to about 1:1, about 1:5 to about 1:1, about 1:1 to about 2:1, or about 1:2 to about 1:1.
 
20. The antigen-presenting surface of any one of embodiments 1-19, wherein the antigen-presenting surface includes glass, metal, ceramic, and/or a metal oxide or any combination thereof.
 
21. The antigen-presenting surface of any one of embodiments 1-20, wherein the antigen-presenting surface includes a polymeric surface.
 
22. The antigen-presenting surface of embodiment 20 or 21, wherein the surface includes a magnetic material.
 
23. The antigen-presenting surface of any one of embodiments 1 to 22, wherein each of the plurality of primary activating molecular ligands is noncovalently bound to a binding moiety, and further wherein the binding moiety is covalently bound to the antigen-presenting surface.
 
24. The antigen-presenting surface of embodiment 23, wherein each of the plurality of primary activating molecular ligands comprises a biotin and is noncovalently bound to a biotin-binding agent, and further wherein the biotin-binding agent is covalently bound to the antigen-presenting surface.
 
25. The antigen-presenting surface of any one of embodiments 1 to 22, wherein each of the plurality of primary activating molecular ligands is noncovalently bound to a binding moiety, and further wherein the binding moiety is noncovalently bound to the antigen-presenting surface.
 
26. The antigen-presenting surface of embodiment 25, wherein each of the plurality of primary activating molecular ligands comprises a biotin moiety, the binding moiety comprises a biotin-binding agent, and the biotin-binding agent is noncovalently bound to a second biotin moiety covalently attached to the antigen-presenting surface.
 
27. The antigen-presenting surface of 24 or 26, wherein the biotin-binding agent is streptavidin.
 
28. The antigen-presenting surface of any one of embodiments 1 to 27, wherein the MHC molecule includes an MHC protein sequence and a beta microglobulin.
 
29. The antigen-presenting surface of any one of embodiments 1 to 28, wherein the MHC molecule further includes a tumor specific antigen.
 
30. The antigen-presenting surface of embodiment 29, wherein the tumor specific antigen is non-covalently associated with the MHC molecule.
 
31. The antigen-presenting surface of embodiment 29 or 30, wherein the antigen is SLC45A2, TCL1, VCX3A, MART1 or NYESO1.
 
32. The antigen-presenting surface of any one of embodiments 1-31, wherein the TCR co-activating molecule includes a protein.
 
33. The antigen-presenting surface of embodiment 32, wherein the TCR co-activating protein molecule includes a CD-28 binding protein or a fragment thereof which retains binding ability with CD28.
 
34. The antigen-presenting surface of embodiment 32 or 33, wherein the TCR co-activating molecule further comprises a site-specific C-terminal biotin moiety.
 
35. The antigen-presenting surface of embodiment 33 or 34, wherein the CD28 binding protein includes a CD80 molecule or a fragment thereof, wherein the fragment retains binding ability to CD28.
 
36. The antigen-presenting surface of any one of embodiments 32-35 wherein the TCR co-activating molecule includes an anti-CD28 antibody or fragment thereof, wherein the fragment retains binding activity with CD28.
 
37. The antigen-presenting surface of any one of embodiments 1-36, wherein the adjunct TCR activating molecular ligand includes a CD2 binding protein or a fragment thereof, wherein the fragment retains binding ability with CD2.
 
38. The antigen-presenting surface of embodiment 37, wherein the CD2 binding protein further comprises a site-specific C-terminal biotin moiety.
 
39. The antigen-presenting surface of embodiment 37 or 38, wherein the adjunct TCR activating molecular ligand includes a CD58 molecule or fragment thereof, wherein the fragment retains binding activity with CD2.
 
40. The antigen-presenting surface of any one of embodiments 1-39, wherein the adjunct TCR activating molecule includes an anti-CD2 antibody or a fragment thereof, wherein the fragment retains binding activity with CD2.
 
41. The antigen-presenting surface of any one of embodiments 1-40, wherein each of the plurality of co-activating molecular ligands is non-covalently attached to a streptavidin wherein the streptavidin is non-covalently attached to a streptavidin binding molecule, further wherein the streptavidin binding molecule is covalently attached via a linker to the antigen-presenting surface, optionally wherein the streptavidin binding molecule comprises biotin.
 
42. The antigen-presenting surface of any one of embodiments 1-40, wherein each of the plurality of co-activating molecular ligands is covalently connected to the surface via a linker.
 
43. The antigen-presenting surface of embodiment 41 or 42, wherein the linker links the streptavidin binding molecule and/or co-activating molecular ligands to the surface through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetween bonds.
 
44. The antigen-presenting surface of any one of embodiments 1-40, wherein each of the plurality of co-activating molecular ligands is non-covalently attached to a streptavidin moiety; and the streptavidin moiety is covalently attached to the antigen-presenting surface.
 
45. The antigen-presenting surface of embodiment 42, wherein the streptavidin moiety is linked by a linker to the surface through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetween.
 
46. The antigen-presenting surface of any one of embodiments 5-45, wherein:
 
(i) each of the plurality of surface-blocking molecular ligands includes a hydrophilic moiety, an amphiphilic moiety, a zwitterionic moiety, and/or a negatively charged moiety;
 
(ii) each of the plurality of surface-blocking molecular ligands includes a linker and a terminal surface-blocking group, optionally wherein the linkers of the plurality of surface-blocking molecular ligands are of the same length or are of different lengths; or
 
(iii) each of the plurality of surface-blocking molecular ligands includes a linker and a terminal surface-blocking group, wherein the terminal surface-blocking group comprises a hydrophilic moiety, amphiphilic moiety, zwitterionic moiety, and/or negatively charged moiety, optionally wherein the linkers of the plurality of surface-blocking molecular ligands are of the same length or are of different lengths.
 
47. The antigen-presenting surface of embodiment 46, wherein:
 
(i) the plurality of surface-blocking molecular ligands all have the same terminal surface-blocking group; or
 
(ii) the plurality of surface-blocking molecular ligands have a mixture of terminal surface-blocking groups; optionally wherein each of the plurality of surface-blocking molecular ligands includes a polyethylene glycol (PEG) moiety, a carboxylic acid moiety, or a combination thereof, further optionally wherein the PEG moiety of each of the surface-blocking molecular ligands has a backbone linear chain length of about 10 atoms to about 100 atoms.
 
48. The antigen-presenting surface of any one of embodiments 5-47, wherein:
 
(i) each of the plurality of surface-blocking molecular ligands is covalently connected to the antigen-presenting surface; and/or
 
(ii) the plurality of the surface-blocking molecular ligands and may include 2, 3, or 4 different surface-blocking groups and/or 2, 3, 4, or more different lengths of linkers, chosen in any combination.
 
49. The antigen-presenting surface of any one of embodiments 1-48, further including a plurality of adhesion stimulatory molecular ligands, optionally wherein each adhesive molecular ligand includes a ligand for a cell adhesion receptor comprising an ICAM protein sequence.
 
50. The antigen-presenting surface of embodiment 49, wherein the adhesion stimulatory molecular ligand is covalently connected to the antigen-presenting surface via a linker.
 
51. The antigen-presenting surface of embodiment 50, wherein the adhesion stimulatory molecular ligand is non-covalently attached to a streptavidin moiety, wherein the streptavidin moiety is covalently attached via a linker to the antigen-presenting surface.
 
52. The antigen-presenting surface of embodiment 50, wherein the adhesion stimulatory molecular ligand is non-covalently attached to a streptavidin, wherein the streptavidin is noncovalently attached to a biotin and the biotin is covalently attached via a linker to the antigen-presenting surface.
 
53. The antigen-presenting surface of any one of embodiments 1-52, wherein the ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is from about 3:1 to about 1:3.
 
54. The antigen-presenting surface of any one of embodiments 1-53, wherein the ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 1:2 to about 2:1.
 
55. The antigen-presenting surface of any one of embodiments 1-54, wherein the ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 1:1.
 
56. The antigen-presenting surface of any one of embodiments 1-55, further including a plurality of growth-stimulatory molecular ligands, wherein each of the growth-stimulatory molecular ligands includes a growth factor receptor ligand.
 
57. The antigen-presenting surface of embodiment 56, wherein the growth factor receptor ligand includes a cytokine or fragment thereof, wherein the fragment retains receptor binding ability, optionally wherein the cytokine comprises IL-21.
 
58. The antigen-presenting surface of any one of the embodiments 1-57, which is an antigen-presenting surface of a bead.
 
59. The antigen-presenting surface of embodiment 58, wherein the bead has a surface area within 10% of the surface area of a sphere having an equal volume or diameter.
 
60. The antigen-presenting surface of embodiment 58, wherein the bead has a surface area exceeding by more than 10% the surface area of a sphere having an equal volume or diameter.
 
61. The antigen-presenting surface of any one of the embodiments 1-57, which is an antigen-presenting surface of a microfluidic device, wafer, or tube.
 
62. The antigen-presenting surface of embodiment 61, further including a first portion and a second portion, wherein the distribution of the plurality of primary activating molecular ligands and the distribution of the plurality of co-activating molecular ligands are located in the first portion of the antigen-presenting surface, and the second portion is configured to substantially exclude the primary activating molecular ligands.
 
63. The antigen-presenting surface of embodiment 62, wherein at least one plurality of surface-blocking molecular ligands is located in the second portion of the at least one inner surface of the antigen-presenting surface.
 
64. The antigen-presenting surface of 62 or 63, wherein the first portion of the antigen-presenting surface further includes a plurality of first regions, each first region including at least a subset of the plurality of the primary activating molecular ligands, wherein each of the plurality of first regions is separated from another of the plurality of first region by the second portion configured to substantially exclude primary activating molecular ligands.
 
65. The antigen-presenting surface of embodiment 64, wherein each of the plurality of first regions including the at least a subset of the plurality of the primary activating molecular ligands further includes a subset of the plurality of the co-activating molecular ligands.
 
66. The antigen-presenting surface of embodiment 64 or 65, wherein each of the plurality of first regions including at least the subset of the plurality of the primary activating molecular ligands has an area of about 0.10 square microns to about 4.0 square microns.
 
67. The antigen-presenting surface of any one of embodiments 64-66, wherein the area of each of the plurality of first regions including at least the subset of the plurality of the primary activating molecular ligands is about 4.0 square microns to about 0.8 square microns.
 
68. The antigen-presenting surface of any one of embodiments 64-67, wherein each of the plurality of first regions further includes at least a subset of a plurality of adhesion stimulatory molecular ligands, and optionally wherein each of the adhesion stimulatory molecular ligands includes a ligand for a cell adhesion receptor comprising an ICAM protein sequence.
 
69. The antigen-presenting surface of any one of embodiments 63-68, wherein the second portion configured to substantially exclude the primary activating molecular ligands is also configured to substantially exclude co-activating molecular ligands.
 
70. The antigen-presenting surface of any one of embodiments 62-69, wherein the second portion configured to substantially exclude the primary activating molecular ligands is further configured to include a plurality of growth stimulatory molecular ligands, wherein each of the growth stimulatory molecular ligands includes a growth factor receptor ligand.
 
71. The antigen-presenting surface of any one of embodiments 62-70, wherein the second portion configured to substantially exclude the primary activating molecular ligands includes a plurality of adhesion stimulatory molecular ligands, wherein each of the adhesion stimulatory molecular ligands includes a ligand for a cell adhesion receptor including an ICAM protein sequence.
 
72. The antigen-presenting surface of any one of embodiments 61-71, which is an antigen-presenting surface of a wafer.
 
73. The antigen-presenting surface of any one of embodiments 61-71, which is an antigen-presenting surface of a tube.
 
74. The antigen-presenting surface of any one of embodiments 61-71, which is an antigen-presenting surface of a microfluidic device.
 
75. The antigen-presenting microfluidic device of embodiment 74, wherein each of the plurality of first regions including at least a subset of the plurality of primary activating molecular ligands is disposed at least one surface within a chamber of the antigen-presenting microfluidic device.
 
76. The antigen-presenting microfluidic device of embodiment 75, wherein the chamber is a sequestration pen.
 
77. The antigen-presenting microfluidic device of embodiments 74-76, wherein the microfluidic device further comprises a flow region for containing a flow of a first fluidic medium; and the sequestration pen comprises an isolation region for containing a second fluidic medium, the isolation region having a single opening, wherein the isolation region of the sequestration pen is an unswept region of the microfluidic device; and a connection region fluidically connecting the isolation region to the flow region; optionally wherein the microfluidic device comprises a microfluidic channel comprising at least a portion of the flow region.
 
78. The antigen-presenting microfluidic device of embodiment 77, wherein the microfluidic device comprises a microfluidic channel comprising at least a portion of the flow region, and the connection region comprises a proximal opening into the microfluidic channel having a width W con  ranging from about 20 microns to about 100 microns and a distal opening into the isolation region, and wherein a length L con  of the connection region from the proximal opening to the distal opening is as least 1.0 times a width W con  of the proximal opening of the connection region.
 
79. The antigen-presenting microfluidic device of embodiment 78, wherein the length L con  of the connection region from the proximal opening to the distal opening is at least 1.5 times the width W con  of the proximal opening of the connection region.
 
80. The antigen-presenting microfluidic device of embodiment 78, wherein the length L con  of the connection region from the proximal opening to the distal opening is at least 2.0 times the width W con  of the proximal opening of the connection region.
 
81. The antigen-presenting microfluidic device of any one of embodiments 78-80, wherein the width W con  of the proximal opening of the connection region ranges from about 20 microns to about 60 microns.
 
82. The antigen-presenting microfluidic device of any one of embodiments 78-81, wherein the length L con  of the connection region from the proximal opening to the distal opening is between about 20 microns and about 500 microns.
 
83. The antigen-presenting microfluidic device of any one of embodiments 78-82, wherein a width of the microfluidic channel at the proximal opening of the connection region is between about 50 microns and about 500 microns.
 
84. The antigen-presenting microfluidic device of any one of embodiments 78-83, wherein a height of the microfluidic channel at the proximal opening of the connection region is between 20 microns and 100 microns.
 
85. The antigen-presenting microfluidic device of any one of embodiments 77-84, wherein the volume of the isolation region ranges from about 2×10 4  to about 2×10 6  cubic microns.
 
86. The antigen-presenting microfluidic device of any one of embodiments 77-85, wherein the proximal opening of the connection region is parallel to a direction of the flow of the first medium in the flow region.
 
87. The antigen-presenting microfluidic device of any one of embodiments 77-86, wherein the microfluidic device comprises an enclosure comprising a base, a microfluidic circuit structure disposed on the base, and a cover which collectively define a microfluidic circuit, and the microfluidic circuit comprises the flow region, the microfluidic channel, and the sequestration pen.
 
88. The antigen-presenting microfluidic device of any one of embodiments 77-87, wherein the microfluidic circuit further comprises one or more inlets through which the first medium can be input into the flow region and one or more outlets through which the first medium can be removed from the flow region.
 
89. The antigen-presenting microfluidic device of embodiment 87, wherein the cover is an integral part of the microfluidic circuit structure.
 
90. The antigen-presenting microfluidic device of embodiment 87 or 88, wherein barriers defining the microfluidic sequestration pen extend from a surface of the base of the microfluidic device to a surface of the cover of the microfluidic device.
 
91. The antigen-presenting microfluidic device of any one of embodiments 87-90, wherein the cover and the base are part of a dielectrophoresis (DEP) mechanism for selectively inducing DEP forces on a micro-object.
 
92. The antigen-presenting microfluidic device of any one of embodiments 87-91, wherein the microfluidic device further comprises a first electrode, an electrode activation substrate, and a second electrode, wherein the first electrode is part of a first wall of the enclosure and the electrode activation substrate and the second electrode is part of a second wall of the enclosure, wherein the electrode activation substrate comprises a photoconductive material, semiconductor integrated circuits, or phototransistors.
 
93. The antigen-presenting microfluidic device of embodiment 92, wherein the first wall of the microfluidic device is the cover, and wherein the second wall of the microfluidic device is the base.
 
94. The antigen-presenting microfluidic device of embodiment 92 or 93, wherein the electrode activation substrate comprises phototransistors.
 
95. The antigen-presenting microfluidic device of any one of embodiments 87-94, wherein the cover and/or the base is transparent to light.
 
96. The antigen-presenting microfluidic device of any one of embodiments 61-95, wherein the second portion is disposed at at least one surface of a microfluidic channel of the antigen-presenting microfluidic device.
 
97. A covalently functionalized synthetic surface including at least one plurality of biotin-binding agent or biotin functionalities and at least one plurality of surface-blocking molecular ligands, wherein each of the biotin-binding agent or biotin functionalities and each of the plurality of surface-blocking molecular ligands are covalently attached to the covalently functionalized synthetic surface.
 
98. The covalently functionalized synthetic surface of embodiment 97, wherein the surface includes the plurality of biotin functionalities.
 
99. The covalently functionalized synthetic surface of embodiment 98, wherein the surface further includes a plurality of biotin-binding agent functionalities noncovalently attached to the surface through the biotin functionalities.
 
100. The covalently functionalized synthetic surface of any one of embodiments 97-99, wherein each of the plurality of biotin functionalities is attached to the covalently functionalized surface via a linker.
 
101. The covalently functionalized synthetic surface of any one of embodiments 97-100, wherein the biotin-binding agent is streptavidin.
 
102. The covalently functionalized synthetic surface of embodiment 97 or 101, wherein each of the plurality of biotin or biotin-binding agent functionalities is attached to the covalently functionalized surface via a linker.
 
103. The covalently functionalized synthetic surface of embodiment 102, wherein the linker linking the biotin or biotin-binding agent functionality has a length of about 20 Angstroms to about 100 Angstroms.
 
104. The covalently functionalized synthetic surface of embodiment 102 or 103, wherein the linker links the biotin-binding agent functionality to the surface through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetween.
 
105. The covalently functionalized synthetic surface of embodiment 102 or 103, wherein the linker links the biotin to the surface through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetween.
 
106. The covalently functionalized synthetic surface of any one of embodiments 102-105, wherein the linker of each biotin or biotin-binding agent functionality includes a polyethylene glycol (PEG) moiety.
 
107. The covalently functionalized synthetic surface of embodiment 106, wherein the PEG linker includes a (PEG) 13  repeating sequence, optionally wherein the surface includes the plurality of biotin-binding agent functionalities.
 
108. The covalently functionalized synthetic surface of embodiment 106, wherein the PEG linker includes a (PEG) 4  repeating sequence, optionally wherein the surface includes the plurality of biotin functionalities.
 
109. The covalently functionalized synthetic surface of any one of embodiments 97-108, wherein:
 
(i) each of the plurality of surface-blocking molecular ligands includes a hydrophilic moiety, an amphiphilic moiety, a zwitterionic moiety, and/or a negatively charged moiety;
 
(ii) each of the plurality of surface-blocking molecular ligands includes a linker and a terminal surface-blocking group, optionally wherein the linkers of the plurality of surface-blocking molecular ligands are of the same length or are of different lengths; or
 
(iii) each of the plurality of surface-blocking molecular ligands includes a linker and a terminal surface-blocking group, wherein the terminal surface-blocking group comprises a hydrophilic moiety, amphiphilic moiety, zwitterionic moiety, and/or negatively charged moiety, optionally wherein the linkers of the plurality of surface-blocking molecular ligands are of the same length or are of different lengths;
 
(iv) each of the plurality of surface-blocking molecular ligands is covalently connected to the antigen-presenting surface; and/or
 
(v) the plurality of the surface-blocking molecular ligands and may include 2, 3, or 4 different surface-blocking groups and/or 2, 3, 4, or more different lengths of linkers, chosen in any combination.
 
110. The covalently functionalized synthetic surface of embodiment 109, wherein:
 
(i) the plurality of surface-blocking molecular ligands all have the same terminal surface-blocking group; or
 
(ii) the plurality of surface-blocking molecular ligands have a mixture of terminal surface-blocking groups; optionally wherein each of the plurality of surface-blocking molecular ligands includes a polyethylene glycol (PEG) moiety, a carboxylic acid moiety, or a combination thereof.
 
111. The covalently functionalized synthetic surface of embodiment 108, wherein the PEG moiety of each of the surface-blocking molecular ligands has a backbone linear chain length of about 10 atoms to about 100 atoms.
 
112. The covalently functionalized synthetic surface of any one of embodiments 97-111, wherein the at least one plurality of streptavidin moieties is disposed upon the covalently functionalized synthetic surface in a density from about 4×10 2  to about 3×10 4  molecules per square micron, in each portion or sub-region where it is attached.
 
113. The covalently functionalized synthetic surface of any one of embodiments 97-111, wherein the at least one plurality of streptavidin moieties is disposed upon the covalently functionalized synthetic surface in a density from about 5×10 3  to about 3×10 4  molecules per square micron, in each portion or sub-region where it is attached.
 
114. The covalently functionalized synthetic surface of any one of embodiments 97-111, wherein the at least one plurality of streptavidin moieties is disposed upon the covalently functionalized synthetic surface from about 6×10 2  to about 5×10 3  molecules per square micron, about 5×10 3  to about 2×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  molecules per square micron, or about 1.25×10 4  to about 1.75×10 4  molecules per square micron, in each portion or sub-region where it is attached.
 
115. The covalently functionalized synthetic surface of any one of embodiments 97-114, wherein the surface includes glass, polymer, metal, ceramic, and/or a metal oxide.
 
116. The covalently functionalized synthetic surface of any one of embodiments 97-115, wherein the covalently functionalized synthetic surface is a covalently functionalized wafer, a covalently functionalized inner surface of a tube, or a covalently functionalized inner surface of a microfluidic device.
 
117. The covalently functionalized synthetic surface of embodiment 116, wherein the tube is a glass or polymer tube.
 
118. The covalently functionalized synthetic surface of any one of embodiments 97 to 115, wherein the covalently functionalized synthetic surface is a covalently functionalized bead.
 
119. The covalently functionalized synthetic surface of embodiment 118, wherein the covalently functionalized bead includes a magnetic material.
 
120. The covalently functionalized synthetic surface of embodiment 118 or 119, wherein the bead has a surface area within 10% of the surface area of a sphere of an equal volume or diameter.
 
121. The covalently functionalized synthetic surface of any one of embodiments 118-120, wherein the at least one plurality of streptavidin or biotin moieties is disposed upon substantially all of the covalently functionalized synthetic surface.
 
122. The covalently functionalized synthetic surface of any one of embodiments 97-117, further including a first portion and a second portion, wherein the distribution of the at least one plurality of streptavidin or biotin functionalities is located in the first portion of the covalently modified synthetic surface, and the distribution of the at least one plurality of the surface-blocking molecular ligands is located in the second portion.
 
123. The covalently functionalized synthetic surface of embodiment 122, wherein a second plurality of surface-blocking molecular ligands is disposed in the first portion of the covalently functionalized synthetic surface.
 
124. The covalently functionalized synthetic surface of embodiment 123, wherein the second plurality of surface-blocking molecular ligands limits the density of functionalizing moieties of an antigen-presenting synthetic surface formed from the covalently functionalized synthetic surface.
 
125. The covalently functionalized synthetic surface of embodiment 123 or 125, wherein the first portion of the covalently functionalized synthetic surface further includes a plurality of first regions, each first region including at least a subset of the plurality of the streptavidin or biotin functionalities, wherein each of the plurality of first regions is separated from another of the plurality of first regions by the second region configured to substantially exclude the streptavidin or biotin functionalities.
 
126. The covalently functionalized synthetic surface of embodiment 125, wherein each of the plurality of first regions including at least the subset of the plurality of the streptavidin or biotin functionalities has an area of about 0.10 square microns to about 4.0 square microns.
 
127. The covalently functionalized synthetic surface of embodiment 125 or 126, wherein the area of each of the plurality of first regions including at least the subset of the plurality of the primary activating molecular ligands is about 4.0 square microns to about 0.8 square microns.
 
128. The covalently functionalized synthetic surface of any one of embodiments 97-116 or 122-127, wherein the covalently functionalized synthetic surface is at least one inner surface of a microfluidic device.
 
129. The covalently functionalized synthetic surface of embodiment 128, wherein each of the plurality of first regions including at least a subset of the plurality of biotin-binding agent or biotin functionalities includes at least one surface within a chamber of the microfluidic device.
 
130. The covalently functionalized synthetic surface of embodiment 129, wherein the chamber is a sequestration pen.
 
131. A kit for preparing an antigen-presenting synthetic surface for activating a T lymphocyte (T cell), including:
 
a. the covalently functionalized synthetic surface of any one of embodiments 95-128, which includes a plurality of noncovalently or covalently associated first coupling agents; and
 
b. a first modification reagent including a plurality of major histocompatibility complex (MHC) I molecules configured to bind with a T cell receptor of the T cell, and further wherein the MHC molecules are configured to bind to one of a first subset of the plurality of noncovalently or covalently associated first coupling agents of the covalently functionalized synthetic surface;
 
optionally wherein the first coupling agents are biotin-binding agents.
 
132. The kit of embodiment 131, wherein each of the plurality of MHC molecules further includes at least one biotin functionality.
 
133. The kit of embodiment 131 or 132, further including a reagent including a plurality of co-activating molecules, each configured to bind one of a second subset of the plurality of noncovalently or covalently associated first coupling agents of the covalently functionalized synthetic surface.
 
134. The kit of embodiment 133, wherein each of the plurality of co-activating molecules includes a biotin functionality.
 
135. The kit of embodiment 134, wherein each of the plurality of co-activating molecules further comprises a site-specific C-terminal biotin moiety.
 
136. The kit of any one of embodiments 133-135, wherein each of the co-activating molecules includes a T cell receptor (TCR) co-activating molecule, an adjunct TCR activating molecule, or any combination thereof.
 
137. The kit of embodiment 136, wherein the plurality of co-activating molecular ligands comprises TCR co-activating molecules and adjunct TCR activating molecules.
 
138. The kit of embodiment 136 or 137, wherein a container containing the reagent including a plurality of co-activating molecules contains the TCR co-activating molecules and/or the adjunct TCR activating molecules of the plurality of co-activating molecular ligands in a ratio from about 100:1 to about 1:100 or in a ratio of about 3:1 to about 1:3.
 
139. The kit of any one of embodiments 136-138, wherein a container containing the reagent including a plurality of co-activating molecules contains the TCR co-activating molecules and the adjunct TCR activating molecules of the plurality of co-activating molecular ligands in a ratio from about 10:1 to about 1:10 or from about 10:1 to about 1:20.
 
140. The kit of any one of embodiments 136-139, wherein the ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is 100:1 to 90:1, 90:1 to 80:1, 80:1 to 70:1, 70:1 to 60:1, 60:1 to 50:1, 50:1 to 40:1, 40:1 to 30:1, 30:1 to 20:1, 20:1 to 10:1, 10:1 to 1:1, 3:1 to 1:3; 1:1 to 1:10, 1:10 to 1:20, 1:20 to 1:30, 1:30 to 1:40, 1:40 to 1:50, 1:50 to 1:60, 1:60 to 1:70, 1:70 to 1:80, 1:80 to 1:90, or 1:90 to 1:100, wherein each of the foregoing values is modified by “about”.
 
141. The kit of any one of embodiments 136-140, wherein a container containing the reagent including a plurality of co-activating molecules contains the TCR co-activating molecules and the adjunct TCR activating molecules of the plurality of co-activating molecular ligands in a ratio from about 20:1 to about 1:20.
 
142. The kit of embodiment 136, wherein the reagent including a plurality of co-activating molecules is contained in two containers, wherein the first container contains T cell receptor (TCR) co-activating molecules, and the second container contains adjunct TCR activating molecules.
 
143. The kit of any one of embodiments 136-142, wherein the TCR co-activating molecule is a CD28 binding protein or a fragment thereof which retains binding ability with CD28.
 
144. The kit of any one of embodiments 136-143, wherein the adjunct TCR co-activating molecule is a CD2 binding protein or a fragment thereof.
 
145. The kit of any one of embodiments 131-144, further including a reagent including adhesion stimulatory molecules, wherein each adhesion stimulatory molecule includes a ligand for a cell adhesion receptor including an ICAM protein sequence configured to react with a third subset of the plurality of noncovalently or covalently associated first coupling agent functionalities of the covalently functionalized synthetic surface.
 
146. The kit of embodiment 145, wherein the adhesion stimulatory molecule includes a biotin functionality.
 
147. The kit of any one of embodiments 131-146, further including a reagent including growth stimulatory molecules, wherein each growth stimulatory molecule includes a includes a growth factor receptor ligand.
 
148. The kit of embodiment 147, wherein the growth factor receptor ligand includes a cytokine or a fragment thereof.
 
149. The kit of embodiment 148, wherein the cytokine includes IL-21 or a fragment thereof.
 
150. The kit of any one of embodiments 147-149, further including one or more additional growth-stimulatory molecules.
 
151. The kit of embodiment 150, wherein the one or more additional growth-stimulatory molecules include IL2 and/or IL7, or fragments thereof.
 
152. The kit of any one of embodiments 148-151, wherein the growth stimulatory molecule is attached to a covalently modified bead.
 
153. The kit of any one of embodiments 131-152, wherein the first coupling agent is streptavidin.
 
154. A method of preparing a covalently functionalized surface including a plurality of biotin-binding agent or biotin functionalities and at least a first plurality of surface-blocking molecular ligands, wherein the method includes: reacting at least a first subset of reactive moieties of an intermediate reactive synthetic surface with a plurality of linking reagents, each linking reagent including biotin-binding agent or biotin; and reacting at least a second subset of reactive moieties of the intermediate reactive synthetic surface with a plurality of surface-blocking molecules, thereby providing the covalently functionalized synthetic surface including at the least one plurality of biotin-binding agent or biotin functionalities and at the least first plurality of surface-blocking molecular ligands.
 
155. The method of embodiment 154, wherein the linking reagents comprise biotin and the method further comprises noncovalently associating a biotin-binding agent with the biotin functionalities.
 
156. The method of embodiment 154 or 155, wherein the reactive moieties of at least first region of the intermediate reactive synthetic surface include azide moieties.
 
157. The method of any one of embodiments 154-156, wherein the reacting of the surface-blocking molecules is performed after the reacting of the linking reagents including biotin-binding agent or biotin functionalities.
 
158. The method of any one of embodiments 154-156, wherein the reacting of the surface-blocking molecules is performed at the same time as the reacting of the plurality of linking reagents.
 
159. The method of any one of embodiments 154-158, wherein the plurality of biotin-binding agent or biotin functionalities and the at least first plurality of surface-blocking molecular ligands are disposed in at least a first region of the covalently functionalized synthetic surface.
 
160. The method of embodiment 159, wherein the covalently functionalized synthetic surface includes a second region wherein the plurality of biotin-binding agent or biotin functionalities is excluded.
 
161. The method of embodiment 160, wherein the at least first plurality of surface-blocking molecular ligands are disposed in the second region of the covalently functionalized synthetic surface.
 
162. The method of embodiment 161, wherein the reacting of the reagent including surface-blocking molecules in the second region of the intermediate reactive synthetic surface is performed before the reacting of the linking reagents including biotin-binding agent or biotin functionalities in the at least first region of the intermediate reactive synthetic surface.
 
163. The method of embodiment 162, further including reacting a second plurality of surface-blocking molecules with a second subset of reactive moieties in the at least first region of the intermediate reactive synthetic surface.
 
164. The method of any one of embodiments 159-163, wherein the reacting of the plurality of biotin-binding agent or biotin functionalities and the reacting of the at least first plurality of surface-blocking molecules is performed at a plurality of sub-regions of the at least first region of the covalently prepared synthetic surface including reactive moieties.
 
165. The method of any one of embodiments 154-164, further including preparing the intermediate reactive synthetic surface, including: reacting at least a first surface preparing reagent including azide reactive moieties with surface-exposed moieties disposed at at least a first region of a reactive synthetic surface.
 
166. The method of embodiment 165, further including reacting a second portion of surface-exposed moieties disposed in a second region of the reactive synthetic surface with a plurality of surface-blocking molecules.
 
167. The method of embodiment 165 or 166, wherein the surface-exposed moieties of the at least first region of the reactive synthetic surface and the surface-exposed moieties of the second region of the reactive synthetic surface are not the same surface-exposed moieties.
 
168. The method of embodiment 166 or 167, wherein the second portion of the reactive synthetic surface includes surface exposed moieties configured to substantially not react with the pluralities of the primary activating and co-activating molecules.
 
169. The method of any one of embodiments 166-168, wherein the reacting the surface-exposed moieties of the second portion of the reactive synthetic surface with the plurality of surface-blocking molecules is performed before reacting the surface exposed moieties of the first portion of synthetic surface with the at least first surface preparing reagent to provide a covalently prepared surface at the first portion of the surface.
 
170. The method of any one of embodiments 165-169, wherein the surface-exposed moieties are nucleophilic moieties.
 
171. The method of any one of embodiments 165-170, wherein the surface-exposed moieties are displaceable moieties.
 
172. The method of any one of embodiments 154-171, wherein the distribution of the plurality of biotin-binding agent or biotin functionalities on the covalently functionalized synthetic surface is from about 6×10 2  to about 5×10 3  molecules per square micron, in each region where it is attached.
 
173. The method of any one of embodiments 154-171, wherein the distribution of the plurality of biotin-binding agent or biotin functionalities on the covalently functionalized synthetic surface is from about 5×10 3  molecules to about 1×10 4  molecules per square micron, in each region where it is attached.
 
174. The method of any one of embodiments 154-171, wherein the distribution of the plurality of biotin-binding agent or biotin functionalities on the covalently functionalized synthetic surface is from about 5×10 3  to about 3×10 4  molecules per square micron, about 5×10 3  to about 2×10 4  molecules per square micron, about 1×10 4  to about 3×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  molecules per square micron, or about 1.25×10 4  to about 1.75×10 4  molecules per square micron, in each region where it is attached.
 
175. The method of any one of embodiments 154-174, wherein the surface is metal, glass, ceramic, polymer, or a metal oxide.
 
176. The method of any one of embodiments 154-175, wherein the surface is a surface of a bead, a surface of a wafer of any configuration, an inner surface of a tube, or at least one inner surface of a microfluidic device.
 
177. The method of embodiment 176, wherein the bead has a surface area within 10% of the surface area of a sphere of an equal volume or diameter.
 
178. The method of embodiment 176, wherein the tube is a glass or polymer tube.
 
179. The method of any one of embodiments 154 or 156-178, wherein the linking reagents include the biotin-binding agent.
 
180. The method of any one of embodiments 154-179, further comprising preparing an antigen-presenting surface for activating a T lymphocyte (T cell), including:
         reacting a plurality of primary activating molecules, each including a major histocompatibility complex (MHC) Class I molecule configured to bind to a T cell receptor (TCR) of the T cell, with a first plurality of binding moieties disposed on a covalently functionalized surface,
 
wherein each of the first plurality of binding moieties is configured for binding the primary activating molecule; and
 
reacting a plurality of co-activating molecules, each including: a TCR co-activating molecule; or an adjunct TCR activating molecule, with a second plurality of binding moieties of the covalently functionalized surface configured for binding the co-activating molecule,
 
thereby providing a plurality of specifically bound primary activating molecular ligands and a plurality of specifically bound co-activating molecular ligands on the antigen-presenting surface.
 
181. A method of preparing an antigen-presenting surface for activating a T lymphocyte (T cell), including: reacting a plurality of primary activating molecules, each including a major histocompatibility complex (MHC) Class I molecule configured to bind to a T cell receptor (TCR) of the T cell, with a first plurality of binding moieties disposed on a covalently functionalized surface,
 
wherein each of the first plurality of binding moieties is configured for binding the primary activating molecule; and
 
reacting a plurality of co-activating molecules, each including: a TCR co-activating molecule; or an adjunct TCR activating molecule, with a second plurality of binding moieties of the covalently functionalized surface configured for binding the co-activating molecule,
 
thereby providing a plurality of specifically bound primary activating molecular ligands and a plurality of specifically bound co-activating molecular ligands on the antigen-presenting surface.
 
182. The method of embodiment 181, wherein the plurality of co-activating molecular ligands comprises TCR co-activating molecules and adjunct TCR activating molecules.
 
183. The method of embodiment 181 or 182, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 100:1 to about 1:100.
 
184. The method of any one of embodiments 181-183, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 10:1 to about 1:10.
 
185. The method of any one of embodiments 181-184, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is 100:1 to 90:1, 90:1 to 80:1, 80:1 to 70:1, 70:1 to 60:1, 60:1 to 50:1, 50:1 to 40:1, 40:1 to 30:1, 30:1 to 20:1, 20:1 to 10:1, 10:1 to 1:1, 3:1 to 1:3; 1:1 to 1:10, 1:10 to 1:20, 1:20 to 1:30, 1:30 to 1:40, 1:40 to 1:50, 1:50 to 1:60, 1:60 to 1:70, 1:70 to 1:80, 1:80 to 1:90, or 1:90 to 1:100, wherein each of the foregoing values is modified by “about”.
 
186. The method of any one of embodiments 181-185, wherein the ratio of the TCR co-activating molecules to the adjunct TCR activating molecules is about 20:1 to about 1:20 or about 3:1 to about 1:3.
 
187. The method of any one of embodiments 181-186, further including reacting a plurality of surface-blocking molecules with a third plurality of binding moieties of the covalently functionalized surface, wherein each of the binding moieties of the third plurality is configured for binding the surface-blocking molecule.
 
188. The method of any one of embodiments 181-187, wherein the MHC molecule includes a protein sequence and a beta microglobulin.
 
189. The method of any one of embodiments 181-188 wherein each of the plurality of primary activating molecules including an MHC molecule further includes a tumor specific antigen.
 
190. The method of embodiment 189, wherein the tumor specific antigen is SLC45A2, TCL1, VCX3A, MART1 or NYESO1.
 
191. The method of any one of embodiments 181-190, further including reacting a plurality of adhesion stimulatory molecular ligands, wherein each adhesion stimulatory molecular ligand includes a ligand for a cell adhesion receptor including an ICAM protein sequence, with a fourth plurality of binding moieties of the covalently functionalized surface, wherein each of the binding moieties of the fourth plurality is configured for binding with the cell adhesion receptor ligand molecule.
 
192. The method of any one of embodiments 181-191, wherein each of the first plurality of binding moieties of the covalently functionalized surface includes a biotin-binding agent or a biotin moiety.
 
193. The method of any one of embodiments 181-192, wherein the first plurality of binding moieties and the second plurality of binding moieties include the same binding moiety.
 
194. The method of any one of embodiments 181-193, wherein the second plurality of binding moieties and the third plurality of binding moieties configured to bind the surface-blocking molecules include the same binding moiety.
 
195. The method of any one of embodiments 181-194, further including producing the covalently functionalized surface including the first plurality of binding moieties by reacting at least a first subset of reactive moieties of an intermediate reactive surface with a first linking reagent each including a binding moiety.
 
196. The method of embodiment 195, wherein the binding moiety is a biotin-binding agent.
 
197. The method of any one of embodiments 193-196, wherein the second plurality of binding moieties is a second sub-set of the at least first plurality of binding moieties.
 
198. The method of any one of embodiments 195-197, wherein the second plurality of binding moieties of the covalently functionalized synthetic surface is a second subset of reactive moieties of the intermediate reactive surface.
 
199. The method of any one of embodiments 187-198, wherein the third plurality of binding moieties configured to bind the surface-blocking molecules is a third sub-set of the at least first plurality of binding moieties.
 
200. The method of any one of embodiments 195-198, wherein the third plurality of binding moieties configured to bind the surface-blocking molecules is a further subset of the reactive moieties of the intermediate reactive bead.
 
201. The method of any one of embodiments 181-200, wherein the covalently functionalized surface includes metal, glass, ceramic, polymer, a metal oxide, or any combination thereof.
 
202. The method of any one of embodiments 181-201, wherein the MHC molecule includes an MHC protein sequence and a beta microglobulin.
 
203. The method of embodiment 202, wherein the MHC molecule is connected to the covalently modified surface via a C-terminal connection of the MHC protein sequence.
 
204. The method of any one of embodiments 181-203, wherein the MHC molecule further includes an antigen specific peptide sequence.
 
205. The method of any one of embodiments 181-204, wherein the density of the plurality of primary activating molecular ligands on the antigen-presenting surface is from about 4×10 2  to about 2×10 3  molecules per square micron, in each portion or sub-region where it is attached.
 
206. The method of any one of embodiments 181-204, wherein the density of the plurality of primary activating molecular ligands on the antigen-presenting surface is from about 2×10 3  to about 5×10 3  molecules per square micron, in each portion or sub-region where it is attached.
 
207. The method of any one of embodiments 181-204, wherein the density of the plurality of primary activating molecular ligands on the antigen-presenting surface is from about 5×10 3  to about 3×10 4  molecules per square micron, about 5×10 3  to about 2×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  molecules per square micron, or about 1.25×10 4  to about 1.75×10 4  molecules per square micron, in each portion or sub-region where it is attached.
 
208. The method of any one of embodiments 181-207, wherein the TCR co-activating molecule includes a CD28 binding protein or a fragment thereof.
 
209. The method of embodiment 209, wherein the CD28 binding protein or the fragment thereof further comprises a site-specific C-terminal biotin moiety.
 
210. The method of any one of embodiments 181-209, wherein the TCR co-activating molecule includes a CD80 molecule or a fragment thereof, wherein the fragment retains binding activity to CD28.
 
211. The method of any one of embodiments 181-209, wherein the TCR co-activating molecule includes an anti-CD28 antibody or a fragment thereof.
 
212. The method of any one of embodiments 181-211, wherein the adjunct TCR activating molecule includes a CD2 binding protein.
 
213. The method of embodiment 212, wherein the CD2 binding protein or the fragment thereof further comprises a site-specific C-terminal biotin moiety.
 
214. The method of any one of embodiments 181-213, wherein the adjunct TCR activating molecule includes a CD58 molecule or a fragment thereof, wherein the fragment retains binding activity with CD2.
 
215. The method of a one of embodiments 181-214, wherein the adjunct TCR activating molecule includes an anti-CD2 antibody or a fragment thereof.
 
216. The method of any one of embodiments 181-215, wherein a ratio of the primary activating molecular ligands to the co-activating molecular ligands on the antigen-presenting surface is about 1:10 to about 2:1, about 1:5 to about 2:1, about 1:2 to about 2:1, about 1:10 to about 1:1, about 1:5 to about 1:1, about 1:1 to about 2:1, or about 1:2 to about 1:1.
 
217. The method of any one of embodiments 181-216, wherein a ratio of the primary activating molecular ligands to the co-activating molecular ligands on the antigen-presenting surface is about 1:1.
 
218. The method of any one of embodiments 181-217, wherein the method produces an antigen-presenting surface according to any one of embodiments 1-96.
 
219. The method of any one of embodiments 181-218, wherein the covalently functionalized surface is a surface of a bead.
 
220. The method of any one of embodiments 181-218, wherein the antigen-presenting surface is an antigen-presenting bead.
 
221. The method of any one of embodiments 219-220, wherein the bead has a surface area within 10% of the surface area of a sphere of an equal volume or diameter.
 
222. The method of any one of embodiments 219-221, wherein the bead comprises glass.
 
223. The method of any one of embodiments 219-222, wherein the bead comprises a polymer.
 
224. The method of any one of embodiments 219-223, wherein the bead comprises a magnetic material.
 
225. The method of any one of embodiments 181-224, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 3:1 to about 1:3.
 
226. The method of any one of embodiments 181-225, wherein the plurality of primary activating molecular ligands is disposed upon the surface of the antigen-presenting bead at a density from about 4×10 2  to about 3×10 4  molecules per square micron.
 
227. The method of any one of embodiments 181-226, wherein the distribution of the plurality of primary activating molecular ligands on the antigen-presenting bead is from about 4×10 2  to about 2×10 3  molecules per square micron.
 
228. The method of any one of embodiments 181-226, wherein the plurality of primary activating molecular ligands is disposed upon at least a portion of a surface of the antigen-presenting bead at a density from about 2×10 3  to about 3×10 4  molecules per square micron.
 
229. The method of any one of embodiments 181-226, wherein the plurality of primary activating molecular ligands is disposed upon at least a portion of a surface of the antigen-presenting bead at a density from about 5×10 3  to about 2×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  molecules per square micron, or about 1.25×10 4  to about 1.75×10 4  molecules per square micron.
 
230. The method of any one of embodiments 219-229, wherein the distribution of the plurality of co-activating molecular ligands is from about 2×10 2  to about 1×10 3  molecules per square micron on the antigen-presenting bead.
 
231. The method of any one of embodiments 219-230, wherein the distribution of the plurality of co-activating molecular ligands on the antigen-presenting bead is from about 1×10 3  to about 2×10 4  molecules per square micron, about 5×10 3  to about 2×10 4  molecules per square micron, about 5×10 3  to about 1.5×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  molecules per square micron, about 1×10 4  to about 1.5×10 4  molecules per square micron, about 1.25×10 4  to about 1.75×10 4  molecules per square micron, or about 1.25×10 4  to about 1.5×10 4  molecules per square micron.
 
232. The method of any one of embodiments 181-218 or 225-231, wherein the covalently functionalized surface is an inner surface of a microfluidic device.
 
233. The method of any one of embodiments 181-218 or 225-229 or 232, wherein the antigen-presenting surface is an antigen-presenting inner surface of a microfluidic device.
 
234. The method of embodiment 233, wherein the microfluidic device comprising the antigen-presenting inner surface is the microfluidic device of any one of embodiments 61-96.
 
235. The method of any one of embodiments 181-218 or 224-229, wherein the covalently functionalized surface is a surface of a wafer.
 
236. The method of any one of embodiments 181-218 or 224-229 or 235, wherein the antigen-presenting surface is an antigen-presenting wafer.
 
237. The method of any one of embodiments 181-218 or 224-2231, wherein the covalently functionalized surface is an inner surface of a tube.
 
238. The method of any one of embodiments 181-218 or 224-229 or 237, wherein the antigen-presenting surface is an antigen-presenting inner surface of a tube.
 
239. The method of any one of embodiments 237 or 238, wherein the tube is (i) a glass tube or (ii) a polymer tube.
 
240. The method of any one of embodiments 181-239, wherein the plurality of primary activating molecules is reacted with the first plurality of binding moieties before the plurality of co-activating molecules is reacted with the second plurality of binding moieties.
 
241. The method of any one of embodiments 154-240, further including producing the intermediate reactive surface, including: reacting at least a first plurality of surface-exposed moieties disposed at at least a first portion of a synthetic reactive surface with a plurality of intermediate preparation molecules including reactive moieties, thereby producing the intermediate reactive surface including a plurality of reactive moieties.
 
242. The method of embodiment 241, wherein producing the intermediate reactive surface further includes reacting at least a second plurality of surface-exposed moieties disposed at the at least first portion of the synthetic reactive surface with a plurality of surface-blocking molecules.
 
243. The method of embodiment 241 or 242, further including reacting a second plurality of surface-exposed moieties disposed in a second portion of the synthetic reactive surface with a plurality of surface-blocking molecules, thereby providing a plurality of surface-blocking molecular ligands at the second portion of the intermediate reactive surface.
 
244. The method of embodiment 243, wherein each surface-blocking molecular ligand is configured to exclude the primary activating molecular ligands including an MHC molecule.
 
245. The method of any one of embodiments 241-244, wherein the surface-exposed moieties are nucleophilic moieties.
 
246. The method of any one of embodiments 241-244, wherein the surface-exposed moieties are displaceable moieties.
 
247. The method of any one of embodiments 241-246, wherein the surface-exposed moieties of the at least first portion of the synthetic reactive surface and the surface-exposed moieties of the second portion of the synthetic reactive surface are not the same surface-exposed moieties.
 
248. The method of any one of embodiments 241-247, wherein the reacting the plurality of primary activating molecules and the reacting the plurality of co-activating molecules is performed at a plurality of sub-regions of the at least first portion of the covalently functionalized surface wherein each sub-region includes the respective first binding moieties, and second binding moieties.
 
249. The method of embodiment 248, further including reacting a plurality of surface-blocking molecules at the plurality of sub-regions of the at least first portion of the covalently functionalized surface including binding moieties.
 
250. The method of embodiment 249, wherein the reacting the plurality of surface-blocking molecules at the plurality of sub-regions of the at least first portion of the covalently functionalized surface is performed before the reacting of the plurality of primary activating molecules and the reacting the plurality of co-activating molecules is performed at the plurality of sub-regions.
 
251. The method of embodiment 248, wherein the reacting of the plurality of surface-blocking molecules at the plurality of sub-regions of the at least first portion of the covalently functionalized surface is performed after the reacting of the plurality of primary activating molecules and the reacting the plurality of co-activating molecules is performed at the plurality of sub-regions.
 
252. The method of any one of embodiments 241-250, wherein each of the plurality of first sub-regions of the covalently functionalized surface is separated from another of the plurality of first sub-regions by a second portion of the covalently functionalized surface.
 
253. The method of embodiment 252, further including reacting a plurality of surface-blocking molecules with respective pluralities of binding moieties located at the second portion of the covalently functionalized surface.
 
254. The method of embodiment 252, wherein the second portion of the intermediate reactive surface includes surface exposed moieties configured to substantially not react with the pluralities of the primary activating and co-activating molecules.
 
255. The method of embodiment 253 or 254, wherein the reacting the surface-exposed moieties of the second portion of the synthetic reactive surface with the plurality of surface-blocking molecules is performed before reacting the surface exposed moieties of the first portion of synthetic reactive surface with one or more surface preparing reagents, thereby providing the intermediate reactive surface.
 
256. The method of any one of embodiments 181-255, wherein reacting the plurality of co-activating molecules is performed after the reacting of the first plurality of molecules including the MHC molecules.
 
257. The method of any one of embodiments 227-256, wherein the MHC molecule is connected to the antigen-presenting surface via a C-terminal connection of the MHC protein sequence.
 
258. The method of any one of embodiments 181-257, wherein the distribution of the plurality of primary activating molecular ligands on the antigen-presenting surface is from about 4×10 2  to about 2×10 3  molecules per square micron in each portion or sub-region of the antigen-presenting surface where the co-activating molecular ligands are present.
 
259. The method of any one of embodiments 181-258, wherein the distribution of the plurality of primary activating molecular ligands on the antigen-presenting surface is from about 2×10 3  to about 5×10 3  molecules per square micron in each portion or sub-region of the antigen-presenting surface where the co-activating molecular ligands are present.
 
260. The method of any one of embodiments 181-258, wherein the distribution of the plurality of primary activating molecular ligands on the antigen-presenting wafer is from about 5×10 3  to about 3×10 4  molecules per square micron, about 5×10 3  to about 2×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  molecules per square micron, or about 1.25×10 4  to about 1.75×10 4  molecules per square micron, in each portion or sub-region of the antigen-presenting surface where the co-activating molecular ligands are present.
 
261. The method of any one of embodiments 181-260, wherein the distribution of the plurality of co-activating molecular ligands is from about 2×10 2  to about 1×10 3  molecules per square micron on the antigen-presenting surface in each portion or sub-region of the antigen-presenting surface where the co-activating molecular ligands are present.
 
262. The method of any one of embodiments 181-260, wherein the distribution of the plurality of co-activating molecular ligands is from about 1×10 3  to about 5×10 3  molecules per square micron on the antigen-presenting surface in each portion or sub-region of the antigen-presenting surface where the co-activating molecular ligands are present.
 
263. The method of any one of embodiments 181-260, wherein the distribution of the plurality of co-activating molecular ligands on the antigen-presenting surface is from about 5×10 3  to about 2×10 4  molecules per square micron, about 5×10 3  to about 1.5×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  molecules per square micron, about 1×10 4  to about 1.5×10 4  molecules per square micron, about 1.25×10 4  to about 1.75×10 4  molecules per square micron, or about 1.25×10 4  to about 1.5×10 4  molecules per square micron in each portion or sub-region of the antigen-presenting surface where the co-activating molecular ligands are present.
 
264. The method of any one of embodiments 154-263, wherein the biotin-binding agent is streptavidin.
 
265. A method of activating T lymphocytes (T cells) including: contacting a plurality of T cells with an antigen-presenting synthetic surface including: a plurality of primary activating molecular ligands, each including a major histocompatibility (MHC) Class I molecule configured to bind to a T cell receptor of the T cell; and a plurality of co-activating molecular ligands each including a T cell receptor (TCR) co-activating molecule or an adjunct TCR activating molecule; and culturing the plurality of T cells in contact with the antigen-presenting synthetic surface, thereby converting at least a portion of the plurality of T cells to activated T cells.
 
266. A method of activating T lymphocytes (T cells) including: contacting a plurality of T cells with the antigen-presenting synthetic surface of any one of embodiments 1-96; and culturing the plurality of T cells in contact with the antigen-presenting synthetic surface, thereby converting at least a portion of the plurality of T cells to activated T cells.
 
267. The method of embodiment 265 or 266, wherein the T cells include CD8+ T cells.
 
268. The method of any one of embodiments 265-267, wherein the plurality of co-activating molecular ligands comprises TCR co-activating molecules and adjunct TCR activating molecules.
 
269. The method of any one of embodiments 265-268, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 100:1 to about 1:100.
 
270. The method of any one of embodiments 265-269, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is 100:1 to 90:1, 90:1 to 80:1, 80:1 to 70:1, 70:1 to 60:1, 60:1 to 50:1, 50:1 to 40:1, 40:1 to 30:1, 30:1 to 20:1, 20:1 to 10:1, 10:1 to 1:1, 3:1 to 1:3; 1:1 to 1:10, 1:10 to 1:20, 1:20 to 1:30, 1:30 to 1:40, 1:40 to 1:50, 1:50 to 1:60, 1:60 to 1:70, 1:70 to 1:80, 1:80 to 1:90, or 1:90 to 1:100, wherein each of the foregoing values is modified by “about”.
 
271. The method of any one of embodiments 265-270, wherein the ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is from about 20:1 to about 1:20 or about 3:1 to about 1:3.
 
272. The method of any one of embodiments 265-271, wherein the plurality of MHC molecules each include an MHC protein sequence and a beta microglobulin.
 
273. The method of embodiment 272, wherein the protein sequence of the MHC molecule is connected to the antigen-presenting synthetic surface via a C-terminal connection of the protein sequence.
 
274. The method of any one of embodiments 265-273, wherein the MHC molecule includes a biotin moiety and is attached to the antigen-presenting synthetic surface via a noncovalent interaction with biotin-binding agent  275 . The method of embodiment 274, wherein the biotin-binding agent s itself covalently bonded to the antigen-presenting synthetic surface.
 
276. The method of embodiment 275, wherein the biotin-binding agent s bonded to the surface through a series of about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetween.
 
277. The method of embodiment 274, wherein the biotin-binding agent is noncovalently associated with the antigen-presenting synthetic surface.
 
278. The method of embodiment 274, wherein the biotin-binding agent is noncovalently associated with a biotin, and the biotin is covalently bonded to the antigen-presenting synthetic surface.
 
279. The method of embodiment 278, wherein the biotin is linked by a linker to the surface through a series of 2 about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 95, 100, 200 bond lengths, or any number of bond lengths therebetween.
 
280. The method of any one of embodiments 274-279, wherein the biotin-binding agent is streptavidin.
 
281. The method of any one of embodiments 265-280, wherein the MHC molecule further includes an antigen molecule.
 
282. The method of embodiment 281, wherein the antigen molecule is SLC45A2, TCL1, VCX3A, MART1 or NYESO1.
 
283. The method of any one of embodiments 265-282, wherein each of the plurality of co-activating molecule ligands is connected to the antigen-presenting synthetic surface.
 
284. The method of any one of embodiments 265-283, wherein the T cell receptor (TCR) co-activating molecule includes a CD28 binding protein or a fragment thereof which retains binding ability to CD28.
 
285. The method of embodiment 284, wherein the CD28 binding protein or the fragment thereof further comprises a site-specific C-terminal biotin moiety.
 
286. The method of any one of embodiments 265-285, wherein the T cell receptor (TCR) co-activating molecule includes a CD80 molecule or a fragment thereof, wherein the fragment retains binding activity to CD28.
 
287. The method of any one of embodiments 265-286, wherein the T cell receptor (TCR) co-activating molecule includes an anti-CD28 antibody or a fragment thereof.
 
288. The method of any one of embodiments 265-287, wherein the adjunct TCR activating molecule includes a CD2 binding protein.
 
289. The method of embodiment 288, wherein the CD2 binding protein or the fragment thereof further comprises a site-specific C-terminal biotin moiety.
 
290. The method of any one of embodiments 265-289, wherein the adjunct TCR activating molecule includes a CD58 molecule or fragment thereof, wherein the fragment retains binding activity with CD2.
 
291. The method of any one of embodiments 265-290, wherein the adjunct TCR activating molecule includes an anti-CD2 antibody or a fragment thereof.
 
292. The method of any one of embodiments 265-291, wherein the plurality of primary activating molecular ligands is present on at least one region of the antigen-presenting surface at a density from about 4×10 2  to about 2×10 3  molecules per square micron, in each portion or sub-region where it is attached.
 
293. The method of any one of embodiments 265-292, wherein the plurality of co-activating molecular ligands is disposed upon at least a portion of the antigen-presenting surface at a density from about 2×10 2  to about 1×10 3  molecules per square micron on the antigen-presenting synthetic surface, in each portion or sub-region where it is attached.
 
294. The method of any one of embodiments 265-292, wherein the plurality of primary activating molecular ligands is disposed upon at least a portion of a surface of the antigen-presenting synthetic surface at a density from about 5×10 3  to about 3×10 4  molecules per square micron, in each portion or sub-region where it is attached.
 
295. The method of any one of embodiments 265-292 or 294, wherein the plurality of co-activating molecular ligands is disposed upon at least a portion of the antigen-presenting synthetic surface at a density from about 5×10 3  to about 2×10 4  molecules per square micron or about 5×10 2  to about 1.5×10 4  molecules per square micron, in each portion or sub-region where it is attached.
 
296. The method of any one of embodiments 265-295, wherein the plurality of primary activating molecular ligands is present on at least one region of the antigen-presenting surface at a density from about 5×10 3  to about 2×10 4 , about 2×10 3  to about 5×10 3 , about 1×10 4  to about 2×10 4 , or about 1.25×10 4  to about 1.75×10 4  molecules per square micron, in each portion or sub-region where it is attached.
 
297. The method of any one of embodiments 265-296, wherein the plurality of co-activating molecular ligands is disposed upon at least a portion of the antigen-presenting surface at a density from about 5×10 3  to about 2×10 4  molecules per square micron, about 5×10 3  to about 1.5×10 4  molecules per square micron, about 1×10 4  to about 2×10 4  per square micron, about 1×10 4  to about 1.5×10 4  per square micron, about 1.25×10 4  to about 1.75×10 4 , or about 1.25×10 4  to about 1.5×10 4  per square micron, in each portion or sub-region where it is attached.
 
298. The method of any one of embodiments 265-297, wherein a ratio of the primary activating molecular ligands to the co-activating molecular ligands on the covalently modified surface is about 1:10 to about 2:1, about 1:5 to about 2:1, about 1:2 to about 2:1, about 1:10 to about 1:1, about 1:5 to about 1:1, about 1:1 to about 2:1, or about 1:2 to about 1:1.
 
299. The method of any one of embodiments 265-298, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 3:1 to about 1:3.
 
300. The method of any one of embodiments 265-299, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 2:1 to about 1:2.
 
301. The method of any one of embodiments 265-300, wherein a ratio of the TCR co-activating molecules to the adjunct TCR activating molecules of the plurality of co-activating molecular ligands is about 1:1.
 
302. The method of any one of embodiments 265-301, further including contacting the plurality of T cells with a plurality of adhesion-stimulating molecular ligands including an ICAM molecule, wherein each of the plurality of adhesion-stimulating molecular ligands is attached to the antigen-presenting synthetic surface.
 
303. The method of embodiment 302, wherein the plurality of adhesion-stimulating molecular ligands is covalently attached to the antigen-presenting synthetic surface.
 
304. The method of any one of embodiments 265-303, wherein the antigen-presenting synthetic surface further includes a plurality of surface-blocking molecular ligands.
 
305. The method of embodiment 304, wherein the plurality of surface-blocking molecular ligands limits the density of the primary activating molecular ligands and/or the density of the co-activating molecular ligands.
 
306. The method of embodiment 304 or 305, wherein the plurality of surface-blocking molecular ligands substantially excludes the plurality of primary activating molecular ligands from a selected region of the covalently modified synthetic surface.
 
307. The method of embodiment 306, wherein the selected region of the antigen-presenting synthetic surface configured to substantially exclude the plurality of primary activating molecular ligands includes a microfluidic channel of a microfluidic device.
 
308. The method of embodiment 306, wherein the plurality of the primary activating molecular ligands is disposed in a plurality of sub-regions of a first portion of the antigen-presenting synthetic surface and the plurality of surface-blocking molecular ligands are disposed in a second region, and further wherein each of the plurality of sub-regions of the first portion of the antigen-presenting synthetic surface is separated from the others of the plurality of sub-regions of the first portion by the second region of the antigen-presenting synthetic surface.
 
309. The method of embodiment 308, wherein the plurality of sub-regions of the first portion of the antigen-presenting synthetic surface further includes a second plurality of surface-blocking molecular ligands.
 
310. The method of embodiments 308 or 309, wherein the plurality of co-activating molecular ligands is disposed in the plurality of sub-regions of the first portion of the antigen-presenting synthetic surface.
 
311. The method of any one of embodiments 265-310, further including contacting the plurality of T cells with a plurality of growth stimulatory molecular ligands.
 
312. The method of embodiment 311, wherein each of the growth stimulatory molecular ligands includes a growth factor receptor ligand.
 
313. The method of embodiment 312, wherein the growth factor receptor ligand includes IL-21 or a fragment thereof.
 
314. The method of any one of embodiments 265-313, wherein the contacting with the plurality of growth stimulatory molecular ligands is performed after a first period of culturing of at least one day.
 
315. The method of any one of embodiments 311-314, wherein the growth factor receptor ligand is connected to the antigen-presenting synthetic surface.
 
316. The method of any one of embodiments 311-315, wherein the plurality of growth factor receptor ligands is connected to an antigen-presenting synthetic surface that is a different surface than the antigen-presenting synthetic surface including the plurality of primary activating molecular ligands.
 
317. The method of any one of embodiments 265-316, wherein the antigen-presenting synthetic surface is the product of any one of embodiments 181-264.
 
318. The method of any one of embodiments 265 to 317, wherein the culturing in contact with the antigen-presenting synthetic surface is performed for a period from about four days to about seven days.
 
319. The method of any one of embodiments 265 to 318, wherein when the antigen-presenting synthetic surface is a bead, the ratio of antigen-presenting beads to cells is about 1:1.
 
320. The method of any one of embodiments 265 to 319, wherein when the antigen-presenting synthetic surface is a bead, the ratio of antigen-presenting beads to cells is about 1:1 at the beginning of the culturing.
 
321. The method of any one of embodiments 265 to 320, further including: completing a first period of activation in contact with the antigen-presenting synthetic surface, wherein the antigen-presenting synthetic surface is a first antigen-presenting synthetic surface; contacting the plurality of activated T cells with a second antigen-presenting synthetic surface including a plurality of primary activating molecular ligands, each including a MHC molecule, and a plurality of co-activating molecular ligands each including a T cell receptor (TCR) co-activating molecule or an adjunct TCR activating molecule; and, culturing the plurality of activated T cells in contact with the second antigen-presenting synthetic surface for a second period of culturing, thereby providing an expanded plurality of activated T cells.
 
322. The method of embodiment 321, wherein the second antigen-presenting synthetic surface is the antigen-presenting bead, antigen-presenting wafer or antigen-presenting microfluidic device of any one of embodiments 1-96 or is the product of any one of embodiments 181-264.
 
323. The method of embodiment 321 or 322, wherein when the first antigen-presenting synthetic surface includes a first plurality of antigen-presenting beads, then the contacting the plurality of activated T cells with the second antigen-presenting synthetic surface includes introducing a second plurality of antigen-presenting beads to the plurality of activated T cells.
 
324. The method of embodiment 323, further including adding the second plurality of antigen-presenting beads in a 1:1 ratio to the plurality of activated T cells.
 
325. The method of embodiment 323 or 324, wherein when the first antigen-presenting synthetic surface includes the antigen-presenting wafer or the antigen-presenting microfluidic device, then the contacting the plurality of activated T cells with the second antigen-presenting synthetic surface includes introducing a plurality of antigen-presenting beads to the plurality of activated T cells.
 
326. The method of any one of embodiments 321-325, further including adding a second plurality of growth stimulatory molecular ligands s during the second culturing period.
 
327. The method of embodiment 326, wherein the second plurality of growth stimulatory molecular ligands is connected to a surface of a bead that is a different bead from the antigen-presenting bead.
 
328. The method of any one of embodiments 321-327, wherein a plurality of IL-2 molecules and a plurality of IL-7 molecules are added to contact the activated T cells for a remainder of the second culturing period.
 
329. The method of any one of embodiments 321-328, wherein the culturing in contact with the second antigen-presenting synthetic surface is performed for a period from about four days to about seven days.
 
330. The method of any one of embodiments 321-329, further including: completing the second period of activation in contact with the second antigen-presenting synthetic surface; contacting the expanded plurality of activated T cells with a third antigen-presenting synthetic surface including a plurality of primary activating molecular ligands, and a plurality of co-activating molecular ligands each including a T cell receptor (TCR) co-activating molecule or an adjunct TCR activating molecule; and, culturing the expanded plurality of activated T cells in contact with the third antigen-presenting synthetic surface for a third period of culturing, thereby providing a plurality of highly activated T cells.
 
331. The method of embodiment 330, wherein the third antigen-presenting synthetic surface is the antigen-presenting bead, the antigen-presenting wafer or the antigen-presenting microfluidic device of any one of embodiments 1-96 or is the product of any one of embodiments 181-264.
 
332. The method of embodiment 330 or 331, further including adding a third plurality of growth stimulatory molecular ligands during the third culturing period.
 
333. The method of embodiment 332, wherein the third plurality of growth stimulatory molecular ligands is connected to a surface of a bead that is a different bead from the third antigen-presenting bead.
 
334. The method of any one of embodiments 330-333, wherein a plurality of IL-2 molecules and a plurality of IL-7 molecules are added to contact the activated T cells for a remainder of the third culturing period.
 
335. The method of any one of embodiments 330-334, wherein the culturing in contact with the third antigen-presenting synthetic surface is performed for a period from about four days to about seven days.
 
336. The method of any one of embodiments 265-335, wherein the activated T cell is CD45RO+.
 
337. The method of any one of embodiments 265-336, wherein the activated T cell is CD28 positive.
 
338. A kit for activating T lymphocytes (T cells), including: an antigen-presenting synthetic surface of any one of embodiments 1-96.
 
339. The kit of embodiment 338, wherein the antigen-presenting synthetic surface is an antigen-presenting bead, an antigen-presenting wafer, an antigen-presenting tube, or an antigen-presenting microfluidic device.
 
340. The kit of embodiment 338 or 339, further including a plurality of covalently modified beads including a plurality of growth-stimulatory molecular ligands, wherein each of the growth-stimulatory molecular ligands includes a growth factor receptor ligand.
 
341. The kit of embodiment 340, wherein the growth factor receptor ligand includes a cytokine or a fragment thereof.
 
342. The kit of embodiment 341, wherein the cytokine includes IL-21 or a fragment thereof.
 
343. The kit of any one of embodiments 340-342, further including one or more additional growth-stimulatory molecules.
 
344. The kit of embodiment 343, wherein the additional growth-stimulatory molecule(s) includes IL2 and/or IL7, or fragments thereof.
 
345. The kit of embodiment 344, wherein the second or more growth stimulatory molecule is attached to a covalently modified bead.
 
346. A method of performing an antigen-specific cytotoxicity assay, comprising:
 
loading one or more target cells into a sequestration pen of a microfluidic device;
 
loading one or more T cells in the sequestration pen, such that the one or more T cells can contact the one or more target cells;
 
contacting the target cells with a detectable marker that labels apoptotic cells; and detecting whether the target cells become apoptotic.
 
347. The method of embodiment 346, wherein the microfluidic device further comprises a microfluidic channel, and wherein the sequestration pen comprises an opening which opens to the microfluidic channel such that the sequestration pen is fluidically connected to the microfluidic channel.
 
348. The method of embodiment 346, wherein the microfluidic device further comprises a flow region for containing a flow of a first fluidic medium; and the sequestration pen comprises an isolation region for containing a second fluidic medium, the isolation region having a single opening, wherein the isolation region of the sequestration pen is an unswept region of the microfluidic device; and a connection region fluidically connecting the isolation region to the flow region; optionally wherein the flow region is a microfluidic channel.
 
349. The method of any one of embodiments 346 to 348, wherein a plurality of target cells are loaded into the sequestration pen.
 
350. The method of any one of embodiments 346 to 348, wherein a single target cell is loaded into the sequestration pen.
 
351. The method of any one of embodiments 346 to 350, wherein a single T cell is loaded into the sequestration pen.
 
352. The method of any one of embodiments 346 to 350, wherein a plurality of T cells are loaded into the sequestration pen.
 
353. The method of any one of embodiments 346 to 352, wherein loading the target cell(s) and/or T cell(s) into the sequestration pen comprises:
 
flowing the target cell(s) and/or T cell(s) into the microfluidic channel; and tilting the microfluidic device such that gravity is able to pull the target cell(s) and/or T cell(s) into the sequestration pen.
 
354. The method of any one of embodiments 346 to 353, wherein the microfluidic device comprises a DEP configuration and DEP force is used to load the target cell(s) and/or T cell(s) into the sequestration pen.
 
355. The method of embodiment 354, wherein the DEP force is activated by structured light.
 
356. The method of any one of embodiments 346 to 355, wherein the detectable marker is provided in a solution that is flowed through the microfluidic channel, whereupon the detectable marker can diffuse from the microfluidic channel into the sequestration pen and contact the target cells.
 
357. The method of any one of embodiments 346 to 356, wherein the detectable marker is an enzymatic substrate.
 
358. The method of any one of embodiments 346 to 357, wherein the detectable marker is a Caspase 3 substrate.
 
359. The method of any one of embodiments 346 to 356, wherein the detectable marker is a labeled antibody that specifically binds to apoptotic cells and/or apoptotic bodies.
 
360. The method of any one of embodiments 346 to 359, wherein detecting whether the target cells become apoptotic is performed periodically.
 
361. The method of any one of embodiments 346 to 360, wherein detecting whether the target cells become apoptotic is performed 2 or more hours after contacting the target cell(s) with the detectable marker.
 
362. The method of any one of embodiments 346 to 361, wherein the target cell(s) are cancer cells.
 
363. The method of any one of embodiments 346 to 362, wherein the target cell(s) are cells from a cell line that express a cancer-associated or cancer-specific antigen.
 
364. The method of any one of embodiments 346 to 363, wherein the target cell(s) express an antigen associated with melanoma, breast cancer, or lung cancer.
 
365. The method of any one of embodiments 346 to 364, wherein the T cells express a chimeric antigen receptor (CAR).
 
366. The method of any one of embodiments 346 to 365, wherein the T cells do not express a chimeric antigen receptor.
 
367. A kit for performing an antigen-specific cytotoxicity assay, comprising:
 
a microfluidic device; and
 
a reagent for detecting apoptotic cells.
 
368. The kit of embodiment 367, wherein the microfluidic device is an antigen-presenting microfluidic device of any one of embodiments 61-96.
 
369. The kit of embodiment 367 or 368, wherein the reagent for detecting apoptotic cells is a enzymatic substrate.
 
370. The kit of embodiment 369, wherein the enzymatic substrate is a Caspase 3 substrate.
 
371. The kit of embodiment 367 or 368 wherein the reagent for detecting apoptotic cells is a labeled antibody that specifically binds to apoptotic cells and/or apoptotic bodies.
 
372. The surface, kit, or method of any one of the preceding embodiments, wherein the surface is an inner surface of a microfluidic device and at least part of the inner surface is in a sequestration pen of the microfluidic device.
 
373. The surface, kit, or method of embodiment 372, or the kit or method of any one of embodiments 346-371 wherein the microfluidic device further comprises a flow region for containing a flow of a first fluidic medium; and the sequestration pen comprises an isolation region for containing a second fluidic medium, the isolation region having a single opening, wherein the isolation region of the sequestration pen is an unswept region of the microfluidic device; and a connection region fluidically connecting the isolation region to the flow region; optionally wherein the microfluidic device comprises a microfluidic channel comprising at least a portion of the flow region.
 
374. The surface, kit, or method of embodiment 373, wherein the microfluidic device comprises a microfluidic channel comprising at least a portion of the flow region, and the connection region comprises a proximal opening into the microfluidic channel having a width W con  ranging from about 20 microns to about 100 microns and a distal opening into the isolation region, and wherein a length L con  of the connection region from the proximal opening to the distal opening is as least 1.0 times a width W con  of the proximal opening of the connection region.
 
375. The surface, kit, or method of embodiment 373, wherein the length L con  of the connection region from the proximal opening to the distal opening is at least 1.5 times the width W con  of the proximal opening of the connection region.
 
376. The surface, kit, or method of embodiment 373, wherein the length L con  of the connection region from the proximal opening to the distal opening is at least 2.0 times the width W con  of the proximal opening of the connection region.
 
377. The surface, kit, or method of any one of embodiments 373-376, wherein the width W con  of the proximal
       

     opening of the connection region ranges from about 20 microns to about 60 microns. 
     378. The surface, kit, or method of any one of embodiments 373-376, wherein the length L con  of the connection region from the proximal opening to the distal opening is between about 20 microns and about 500 microns.
 
379. The surface, kit, or method of any one of embodiments 373-378, wherein a width of the microfluidic channel at the proximal opening of the connection region is between about 50 microns and about 500 microns.
 
380. The surface, kit, or method of any one of embodiments 373-379, wherein a height of the microfluidic channel at the proximal opening of the connection region is between 20 microns and 100 microns.
 
381. The surface, kit, or method of any one of embodiments 373-380, wherein the volume of the isolation region ranges from about 2×10 4  to about 2×10 6  cubic microns.
 
382. The surface, kit, or method of any one of embodiments 373-381, wherein the proximal opening of the connection region is parallel to a direction of the flow of the first medium in the flow region.
 
383. The surface, kit, or method of any one of embodiments 363-382, wherein the microfluidic device comprises an enclosure comprising a base, a microfluidic circuit structure disposed on the base, and a cover which collectively define a microfluidic circuit, and the microfluidic circuit comprises the flow region, the microfluidic channel, and the sequestration pen.
 
384. The surface, kit, or method of embodiment 383, wherein the microfluidic circuit further comprises one or more inlets through which the first medium can be input into the flow region and one or more outlets through which the first medium can be removed from the flow region.
 
385. The surface, kit, or method of embodiment 383 or 384, wherein the cover is an integral part of the microfluidic circuit structure.
 
386. The surface, kit, or method of any one of embodiments 383-385, wherein barriers defining the microfluidic sequestration pen extend from a surface of the base of the microfluidic device to a surface of the cover of the microfluidic device.
 
387. The surface, kit, or method of any one of embodiments 383-386, wherein the cover and the base are part of a dielectrophoresis (DEP) mechanism for selectively inducing DEP forces on a micro-object.
 
388. The surface, kit, or method of any one of embodiments 383-387, wherein the microfluidic device further comprises a first electrode, an electrode activation substrate, and a second electrode, wherein the first electrode is part of a first wall of the enclosure and the electrode activation substrate and the second electrode is part of a second wall of the enclosure, wherein the electrode activation substrate comprises a photoconductive material, semiconductor integrated circuits, or phototransistors.
 
389. The surface, kit, or method of embodiment 388, wherein the first wall of the microfluidic device is the cover, and wherein the second wall of the microfluidic device is the base.
 
390. The surface, kit, or method of embodiment 388 or 389, wherein the electrode activation substrate comprises phototransistors.
 
391. The surface, kit, or method of any one of embodiments 383-390, wherein the cover and/or the base is transparent to light.
 
392. One or more activated T cells produced by the method of any one of embodiments 265 to 337.
 
393. A population of T cells comprising activated T cells produced by the method of any one of embodiments 265-337.
 
394. The cell or population of embodiment 392 or 393, wherein the activated T cells are CD45RO+.
 
395. The cell or population of any one of embodiments 392-394, wherein the activated T cells are CD28+.
 
396. The cell, population, or method of any one of embodiments 265-337 or 392-395, wherein the activated T cells are CD28high.
 
397. The cell, population, or method of any one of embodiments 265-337 or 392-396, wherein the activated T cells are CD127+.
 
398. The cell, population, or method of any one of embodiments 265-337 or 392-397, wherein the activated T cells are CD197+.
 
399. The cell, population, or method of any one of embodiments 265-337 or 392-398, wherein the activated T cells are CD8+.
 
400. A microfluidic device comprising the cell or population of any one of embodiments 392-399.
 
401. The microfluidic device of any one of embodiments 61-96, comprising the cell or population of any one of embodiments 392-399.
 
402. A pharmaceutical composition comprising the cell or population of any one of embodiments 392-399.
 
403. The method of any one of embodiments 257-327, 362-381. or 382-389, wherein the method produces a population of T cells, wherein at least 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% of the population of T cells are antigen-specific T cells, wherein each of the foregoing values are modified by “about.”.
 
404. The method of embodiment 403, wherein 1%-2%, 2%-3%, 3%-4%, 4%-5%, 5%-6%, 6%-7%, 7%-8%, 8%-9%, 9%-10%, 10%-11%, or 11%-12% of the T cells are antigen-specific T cells wherein each of the foregoing values are modified by “about.”.
 
405. The method of embodiment 403 or 404, wherein at least 65%, 70%, 75%, 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 98% of the antigen-specific T cells are CD45RO+/CD28High cells, wherein each of the foregoing values are modified by “about.”
 
406. A method of treating a subject in need of treating a cancer; including: obtaining a plurality of T lymphocytes (T cells) from the subject; contacting the plurality of T cells with an antigen-presenting synthetic surface including a plurality of major histocompatibility complex (MHC) I molecules configured to bind to a T cell receptor of each of the plurality of T cells, wherein the MHC molecules include an antigen specific for the cancer of the subject and wherein the antigen-presenting synthetic surface is the antigen-presenting synthetic surface of any one of embodiments 1-96 or produced according to a method of any one of embodiments 181-264; producing a plurality of activated T cells, wherein the activation is configured to be specific against the cancer of the subject; separating the plurality of specific activated T cells from unactivated cells; and, introducing the plurality of antigen-specific activated T cells into the subject.
 
407. The method of embodiment 406, wherein the T cells are activated using the method of any one of embodiments 365-337.
 
408. The method of embodiment 406 or 407, further including enriching the sample including T lymphocytes before contacting the T lymphocytes with the covalently modified synthetic surface.
 
409. The method of any one of embodiments 406-408, wherein the separating the plurality of antigen-specific activated T cells further includes detecting a plurality of surface biomarkers of the antigen-specific activated T cells.
 
410. The method of embodiment 409, wherein the plurality of surface biomarkers comprises CD45RO+.
 
411. The method of embodiment 409 or 410, wherein the plurality of surface biomarkers comprises CD28+.
 
412. The method of any one of embodiments 409-411, wherein plurality of surface biomarker comprises CD28 high .
 
413. The method of any one of embodiments 409-412, wherein plurality of surface biomarkers comprises CD8.
 
414. The method of any one of embodiments 409-413, wherein plurality of surface biomarkers comprises CD127.
 
415. The method of any one of embodiments 409-414, wherein plurality of surface biomarkers comprises CD197.
 
416. The method of any one of embodiments 406-415, further including rapidly expanding the antigen-specific activated T cells to provide an expanded population of antigen-specific activated T cells.
 
417. The method of embodiment 416, wherein the rapid expansion is performed after separating the specific activated T cells from the unactivated T cells.
 
418. The method of any one of embodiments 406-417, wherein the method of treating the subject delays or stops progression of the cancer in the subject.