Patent Publication Number: US-2021171601-A1

Title: Leucine zipper-based compositions and methods of use

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of International Patent Application No. PCT/US19/46758, filed Aug. 16, 2019, which claims priority to U.S. Provisional Application No. 62/765,058, filed on Aug. 16, 2018, and U.S. Provisional Application No. 62/798,168, filed Jan. 29, 2019, the contents of each of which are incorporated by reference in their entirety, and to each of which priority is claimed. 
    
    
     SEQUENCE LISTING 
     The specification further incorporates by reference the Sequence Listing submitted herewith via EFS on Feb. 16, 2021. Pursuant to 37 C.F.R. § 1.52(e)(5), the Sequence Listing text file, identified as 072734_1205_SL.txt, is 138,031 bytes and was created on Feb. 16, 2021. The Sequence Listing electronically filed herewith, does not extend beyond the scope of the specification and thus does not contain new matter. 
     INTRODUCTION 
     The presently disclosed subject matter provides compositions and systems for cell-based immunotherapy. It relates to systems comprising a membrane-bound polypeptide and a soluble polypeptide, and methods of using the same. 
     BACKGROUND OF THE INVENTION 
     Cell-based immunotherapy or adoptive cell therapy is a therapy with curative potential for the treatment of cancer. T cells and other immune cells may be modified to target tumor antigens through the introduction of Chimeric Antigen Receptors (CARs) specific to selected antigens. Targeted T cell therapy using CARs has shown recent clinical success in treating hematologic malignancies. To ensure potent cancer eradication with minimal toxicity, CAR-based therapy may require targeting multiple tumor antigens, and that generally requires putting larger recombinant constructs into T cells and other immune cells. However, it is difficult to stably integrate large amounts of genetic information into primary T cells with the needed efficiency; this is a technical limitation of current cellular engineering. Both retroviruses and lentiviruses exhibit a significant decrease in viral titer as the viral vector insert approaches and exceeds the packaging limit of the virus (about 6-8 kb for retroviruses and about 10-12 kb for lentiviruses). Low viral titers result in low transduction efficiency and low copy number integrations per cell, leading to inferior levels of gene construct expression. Accordingly, there is a need for novel genetic engineering strategies to express larger CAR constructs targeting multiple antigens, and for therapeutic strategies capable of inducing potent cancer eradication with minimal toxicity and off-target activity. 
     SUMMARY OF THE INVENTION 
     The presently disclosed subject matter provides a system, comprising: a) a membrane-bound polypeptide comprising: i) a transmembrane domain, ii) an intracellular domain, and iii) an extracellular domain that comprises a first dimerization domain and a blocking spacer, and b) a soluble polypeptide comprising i) a second dimerization domain, and ii) an antigen binding domain that binds to an antigen. In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain, and the blocking spacer prevents dimerization of the membrane-bound polypeptide with the soluble polypeptide when the membrane-bound polypeptide and the soluble polypeptide are not expressed from the same cell. 
     In certain embodiments, the blocking spacer has a length of no more than about 25 amino acids. In certain embodiments, the blocking spacer has a length of between about 5 amino acids and about 25 amino acids. In certain embodiments, the blocking spacer is a truncated CD28 spacer or an IgG1 hinge. 
     The presently disclosed subject matter provides a system, comprising: a) a membrane-bound polypeptide comprising: i) a transmembrane domain, ii) an intracellular domain, and iii) an extracellular domain that comprises a first dimerization domain and a second dimerization domain that is capable of dimerizing with the first dimerization domain, and b) a soluble polypeptide comprising i) a third dimerization domain that is capable of dimerizing with the first dimerization domain, and ii) an antigen binding domain that binds to an antigen. In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain. 
     In certain embodiments, the antigen is selected from the group consisting of tumor antigens, pathogen antigens, immune checkpoint molecules, activating receptors, and biomarkers of a hematopoietic lineage cell. In certain embodiments, the antigen is a tumor antigen. In certain embodiments, the tumor antigen is selected from the group consisting of CD2, CD3, CD4, CD5, CD7, CD8, CD19, CD20, CD22, VpreB, CD30, CD33, CD38, CD40, CD44v6, CD70, CD79a, CD79b, CLL-1/CLEC12A, CD123, IL-3R complex, TIM-3, BCMA, TACI, SLAMF7, CD244, Epcam, E-cadherin, B7-H3 (also known as “CD276”), B7-H4, and combinations thereof. 
     In certain embodiments, the antigen is an activating receptor. In certain embodiments, the binding of the antigen binding domain to the activating receptor is capable of activating an antigen presenting cell (APC). In certain embodiments, the APC is a professional APC. In certain embodiments, the professional APC is selected from the group consisting of dendritic cells, macrophages, B cells, and combinations thereof. In certain embodiments, the APC is a non-professional APC. In certain embodiments, the APC is a cell of the myeloid lineage. In certain embodiments, the cell of myeloid lineage is selected from the group consisting of dendritic cells, macrophages, monocytes and combinations thereof. In certain embodiments, the activating receptor is selected from the group consisting of CD40, Toll Like Receptors (TLRs), FLT3, RANK, GM-CSF receptor, and combinations thereof. 
     In certain embodiments, the antigen is an immune checkpoint molecule. In certain embodiments, binding of the antigen binding domain to the immune checkpoint molecule is capable of blocking an immune checkpoint signal in an immunoresponsive cell. In certain embodiments, the immune checkpoint molecule is selected from the group consisting of PD-L1, CD200, B7-H3, B7-H4, HVEM, Galectin9, PD-1, CTLA-4, CD200R, TIM-3, Lag-3, TIGIT, and combinations thereof. 
     In certain embodiments, the antigen is a biomarker of a hematopoietic lineage cell. In certain embodiments, the biomarker of a hematopoietic lineage cell is selected from the group consisting of CD3, CD16, CD33, c-Kit, CD161, CD19, CD20, VpreB, luteinizing hormone receptor (LHCGR), CD123, IL-3R complex, CLEC12A/CLL-1, and combinations thereof. In certain embodiments, the system comprises at least four soluble polypeptides, wherein the antigen binding domain of each soluble polypeptide binds to a different biomarker of a hematopoietic lineage cell. In certain embodiments, each of the at least four soluble polypeptides comprises a dimerization domain that comprises a leucine zipper domain. In certain embodiments, the system comprises a first soluble polypeptide that binds to CD3, a second soluble polypeptide that binds to CD19, a third soluble polypeptide that binds to CD161 and a fourth soluble polypeptide that binds to c-Kit. 
     In certain embodiments, the system further comprises c) a chimeric antigen receptor (CAR) comprising a second antigen binding domain that binds to a second antigen, a transmembrane domain, and an intracellular activating domain. In certain embodiments, the system further comprises d) an inhibitory receptor comprising a leucine zipper domain, wherein the inhibitory receptor binds to a third antigen. In certain embodiments, the inhibitory receptor is a tyrosine phosphatase-based inhibitory receptor. In certain embodiments, the tyrosine phosphatase is selected from the group consisting of PTPRJ, PTPRC, PTPN22, and PTPN6. In certain embodiments, the inhibitory receptor constitutively inhibits and/or deactivates the CAR in the absence of the third antigen. In certain embodiments, binding of the inhibitory receptor to the third antigen prevents the inhibition and/or deactivation of the CAR by the inhibitory receptor. 
     The presently disclosed subject matter provides a system, comprising: a) a membrane-bound polypeptide comprising a transmembrane domain, an intracellular domain and an extracellular domain that comprises a first dimerization domain, and b) a soluble polypeptide comprising a second dimerization domain that is capable of dimerizing with the first dimerization domain, and a cytokine or a chemokine. In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain. 
     In certain embodiments, the cytokine is selected from the group consisting of IL-1, IL-2, IL-3, IL-7, IL-10, IL-12, IL-15, IL-17, IL-18, IL-21, IL-22, IL-36, and combinations thereof. 
     In certain embodiments, the chemokine is selected from the group consisting of CCL1, CCL8, CCL16, CCL17, CCL18, CCL22, and combinations thereof. 
     In certain embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a third dimerization domain, and wherein the second dimerization domain is capable of dimerizing with the first dimerization domain prior to dimerization between the first dimerization domain and the third dimerization domain. 
     For any systems disclosed herewith, in certain embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a linker between the first dimerization domain and the second dimerization domain. In certain embodiments, the linker comprises the amino acid sequence set forth in SEQ ID NO: 3. 
     For any systems disclosed herewith, in certain embodiments, the membrane-bound polypeptide and/or the soluble polypeptide further comprises a tag. In certain embodiments, the tag comprises an epitope tag that is recognized by a first antibody. In certain embodiments, the epitope tag is selected from the group consisting of a Myc-tag, a HA-tag, a Flag-tag, a V5-tag, a T7-tag, and combinations thereof. In certain embodiments, the tag comprises an affinity tag that binds to a substrate. In certain embodiments, the affinity tag is selected from the group consisting of a His-tag, a Strep-tag, an E-tag, a streptavidin binding protein tag (SBP-tag), and combinations thereof. In certain embodiments, the membrane-bound polypeptide and/or the soluble polypeptide further comprises a mimotope recognized by an antibody, wherein binding of the antibody to the mimotope mediates depletion of a cell comprising the membrane-bound polypeptide. In certain embodiments, the mimotope is CD20. 
     For any systems disclosed herewith, in certain embodiments, the intracellular domain of the membrane-bound polypeptide comprises one or more immune activating molecules. In certain embodiments, the intracellular domain does not comprise one or more immune activating molecules. 
     For any systems disclosed herewith, in certain embodiments, the first dimerization domain comprises the amino acid sequence set forth in SEQ ID NO: 1, SEQ ID NO: 2, or SEQ ID NO: 67, and each of the second and third dimerization domains comprise the amino acid sequence set forth in SEQ ID NO: 2, SEQ ID NO: 1, or SEQ ID NO: 67. In certain embodiments, the soluble polypeptide and the membrane-bound polypeptide are capable of forming a dimer when expressed from the same cell. In certain embodiments, the soluble polypeptide and the membrane-bound polypeptide are not capable of forming a dimer when expressed from different cells due to the dimerization between the first dimerization domain and the second dimerization domain of the membrane-bound polypeptide. 
     For any systems disclosed herewith, in certain embodiments, the intracellular domain of the membrane-bound polypeptide comprises a CD3ζ domain, a costimulatory domain, or a fragment or a combination thereof. 
     For any systems disclosed herewith, in certain embodiments, the system further comprises a suicide module. In certain embodiments, the suicide module is an inducible Caspase 9 polypeptide (iCasp9). 
     For any systems disclosed herewith, in certain embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a spacer/hinge domain between the first dimerization domain and the transmembrane domain. In certain embodiments, the spacer/hinge domain comprises an epitope recognized by an antibody, wherein binding of the antibody to the epitope mediates depletion of a cell comprising the membrane-bound polypeptide. In certain embodiments, the spacer/hinge domain comprises a Thy1.1 molecule, a circular CD20 mimotope, or a truncated EGFR molecule (EGFRt). 
     For any systems disclosed herewith, in certain embodiments, the antigen binding domain of the soluble polypeptide comprises a single-chain variable fragment (scFv), a soluble ligand, a cytokine, a non-scFv-based antigen recognition motif, or a fragment or a combination thereof. 
     For any systems disclosed herewith, in certain embodiments, the membrane-bound polypeptide is expressed from a first vector. In certain embodiments, the soluble polypeptide is expressed from a second vector. In certain embodiments, the first vector and/or the second vector is a viral vector or a transposon-based vector. 
     For any systems disclosed herewith, in certain embodiments, the leucine zippers are orthogonal zippers. 
     For any systems disclosed herewith, in certain embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a co-stimulatory ligand or a fragment thereof. In certain embodiments, the co-stimulatory ligand is selected from the group consisting of tumor necrosis factor (TNF) family members, immunoglobulin (Ig) superfamily members, and combinations thereof. 
     In certain embodiments, the TNF family member is selected from the group consisting of 4-1BBL, OX40L, CD70, GITRL, CD40L, CD30L, and combinations thereof. In certain embodiments, the co-stimulatory ligand is CD30L. 
     In certain embodiments, the Ig superfamily member is selected from the group consisting of CD80, CD86, ICOSLG, and combinations thereof. 
     In certain embodiments, the extracellular domain further comprises a dominant negative form of a molecule a fragment thereof. In certain embodiments, the molecule is selected from the group consisting of inhibitors of immune checkpoint molecules, tumor necrosis factor receptor superfamily (TNFRSF) members, Transforming growth factor beta (TGFβ) receptors, and combinations thereof. In certain embodiment, the immune checkpoint molecule is selected from the group consisting of PD-1, CTLA-4, B7-H3, B7-H4, BTLA, TIM-3, LAG-3, TIGIT, LAIR1, CD200, CD200R, HVEM, 2B4, CD160, Galectin9, and combination thereof. In certain embodiments, the immune checkpoint molecule is PD-1. In certain embodiments, the TNFRSF member is selected from the group consisting of Fas, a Tumor necrosis factor receptor, OX40, CD40, CD27, CD30, 4-1BB (also known as “CD137”), and combinations thereof. In certain embodiments, the dominant negative receptor comprises an extracellular domain of TGFβRII or a fragment thereof. 
     The presently disclosed subject matter provides cells comprising a system disclosed herein. In certain embodiments, the cell is an immunoresponsive cell. In certain embodiments, the cell is a cell of the lymphoid lineage or a cell of the myeloid lineage. In certain embodiments, the cell is selected from the group consisting of a T cell, a Natural Killer (NK) cell, and a stem cell from which lymphoid cells may be differentiated. In certain embodiments, the stem cell is a pluripotent stem cell. In certain embodiments, the pluripotent stem cell is an embryonic stem cell or an induced pluripotent stem cell. In certain embodiments, the cell is a T cell. In certain embodiments, the T cell is selected from the group consisting of a cytotoxic T lymphocytes (CTL), a regulatory T cell, a and Natural Killer T (NKT) cell. In certain embodiments, the cell is a regulatory T cell. In certain embodiments, the cell is autologous. In certain embodiments, the cell is allogeneic. 
     The presently disclosed subject matter provides pharmaceutical compositions comprising the cell disclosed herein and one or more pharmaceutically acceptable excipients. 
     The presently disclosed subject matter provides methods for increasing an immune activity of an immunoresponsive cell, comprising introducing to an effective amount of the cells or a system disclosed herein to the immunoresponsive cell. 
     The presently disclosed subject matter provides a method for reducing tumor burden in a subject, comprising administering to a subject an effective amount of the cells or the pharmaceutical compositions disclosed herein. In certain embodiments, the method reduces the number of tumor cells, reduces tumor size, and/or eradicates the tumor in the subject. 
     The presently disclosed subject matter provides a method for treating and/or preventing a neoplasm in a subject, comprising administering to the subject an effective amount of the cells or the pharmaceutical compositions disclosed herein. 
     The presently disclosed subject matter provides a method for activating an antigen presenting cell (APC) in a subject, comprising administering to the subject an effective amount of the cells or the pharmaceutical compositions disclosed herein. 
     The presently disclosed subject matter provides a nucleic acid composition comprising (a) a first polynucleotide encoding a membrane-bound polypeptide comprising: i) a transmembrane domain, ii) an intracellular domain, and iii) an extracellular domain that comprises a first dimerization domain and a blocking spacer, and (b) a second polynucleotide encoding a soluble polypeptide comprising i) a second dimerization domain, and ii) an antigen binding domain that binds to an antigen. In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain, and the blocking spacer prevents the dimerization of the membrane-bound polypeptide with the soluble polypeptide when the membrane-bound polypeptide and the soluble polypeptide are not expressed from the same cell. 
     The presently disclosed subject matter provides a nucleic acid composition comprising (a) a first polynucleotide encoding a membrane-bound polypeptide comprising: i) a transmembrane domain, ii) an intracellular domain, and iii) an extracellular domain that comprises a first dimerization domain and a second dimerization domain that is capable of dimerizing with the first dimerization domain, and (b) a second polynucleotide encoding a soluble polypeptide comprising i) a third dimerization domain that is capable of dimerizing with the first dimerization domain, and ii) an antigen binding domain that binds to an antigen. In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain. 
     The presently disclosed subject matter provides a nucleic acid composition comprising (a) a first polynucleotide encoding a membrane-bound polypeptide comprising a transmembrane domain and an extracellular domain comprising a first dimerization domain, and (b) a second polynucleotide encoding a soluble polypeptide comprising a second dimerization domain that is capable of dimerizing with the first dimerization domain, and a cytokine or chemokine. In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain. 
     In certain embodiments, the first polynucleotide is encoded by a first vector, and the second polynucleotide is encoded by a second vector. In certain embodiments, the first vector and/or the second vector is a viral vector. In certain embodiments, the viral vector is a retroviral vector. In certain embodiments, the retroviral vector is a lentiviral vector. In certain embodiments, the first vector and/or the second vector is a transposon-based vector. In certain embodiments, the first vector is the same as the second vector. In certain embodiments, the first vector is the same as the second vector, for example, the vector backbone for the first and the second vectors can be the same, while the polypeptide or protein encoded/expressed by the first and second vectors can be different. 
     The presently disclosed subject matter also provides a combination of vectors comprising any nucleic acid composition disclosed herein. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The following Detailed Description, given by way of example but not intended to limit the invention to specific embodiments described, may be understood in conjunction with the accompanying drawings. 
         FIG. 1  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 2  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 3  depicts “painting” behavior of leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 4  depicts expression of leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter in T cells. 
         FIG. 5  depicts the differences of “painting” of ZipR-CAR CD8 alpha hinge and IgG1 hinge. 
         FIG. 6  depicts cytotoxicity activity of leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 7  depicts cytotoxicity activity of leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 8  depicts function of leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 9  depicts cytotoxicity activity of leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 10  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 11  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 12  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 13  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 14  depicts activity of canonical CAR—constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 15  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 16  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 17  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 18  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 19  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 20  depicts leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter. 
         FIG. 21  depicts leucine zipper-based chemotherapy-free HCT conditioning regimen model system. 
         FIG. 22  depicts that promotion of fratricide by T cells expressing CD3 CAR. 
         FIG. 23  depicts activity of T cells expressing Kit-CAR targeting CD117/Kit. 
         FIG. 24  depicts activity of CLL-1/CLEC12A CAR. 
         FIGS. 25A-25C  depict activity of leucine zipper-based constructs in accordance with certain embodiments of the presently disclosed subject matter.  FIGS. 25A and 25B  show expression ZipR-CAR.  FIG. 25C  shows cell killing activity of ZipR-CAR. 
         FIGS. 26A and 26B  depict systems comprising chemokine-appended leucine zipper construct and their activities.  FIG. 26A  depicts systems comprising chemokine-appended RR12EE345L leucine zipper and EE12RR345L 28z leucine zipper-based ZipR-CAR. CCL17 and CCL22 interact with CCR4; and CCL1 interacts with CCR8.  FIG. 26B  shows lysis of EL4 expressing CCR4 or CCR8 by the systems. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The presently disclosed subject matter provides systems and use of the systems for immunotherapy. The systems comprise a membrane-bound polypeptide and a soluble polypeptide, wherein the soluble polypeptide is capable of dimerizing with the membrane-bound polypeptide. The systems can enhance immune activity of an immunoresponsive cell. 
     1. Definition 
     Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which this invention belongs. The following references provide one of skill with a general definition of many of the terms used in this invention: Singleton et al., Dictionary of Microbiology and Molecular Biology (2nd ed. 1994); The Cambridge Dictionary of Science and Technology (Walker ed., 1988); The Glossary of Genetics, 5th Ed., R. Rieger et al. (eds.), Springer Verlag (1991); and Hale &amp; Marham, The Harper Collins Dictionary of Biology (1991). As used herein, the following terms have the meanings ascribed to them below, unless specified otherwise. 
     As used herein, the term “about” or “approximately” means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, “about” can mean within 3 or more than 3 standard deviations, per the practice in the art. Alternatively, “about” can mean a range of up to 20%, preferably up to 10%, more preferably up to 5%, and more preferably still up to 1% of a given value. Alternatively, particularly with respect to biological systems or processes, the term can mean within an order of magnitude, preferably within 5-fold, and more preferably within 2-fold, of a value. 
     As used herein, the term “antibody” means not only intact antibody molecules, but also fragments of antibody molecules that retain immunogen-binding ability. Such fragments are also well known in the art and are regularly employed both in vitro and in vivo. Accordingly, as used herein, the term “antibody” means not only intact immunoglobulin molecules but also the well-known active fragments F(ab′) 2 , and Fab. F(ab′) 2 , and Fab fragments that lack the Fc fragment of intact antibody, clear more rapidly from the circulation, and may have less non-specific tissue binding of an intact antibody (Wahl et al.,  J. Nucl. Med.  24:316-325 (1983)). The antibodies of the invention comprise whole native antibodies, bispecific antibodies; chimeric antibodies; Fab, Fab′, single chain V region fragments (scFv), fusion polypeptides, and unconventional antibodies. In certain embodiments, an antibody is a glycoprotein comprising at least two heavy (H) chains and two light (L) chains inter-connected by disulfide bonds. Each heavy chain is comprised of a heavy chain variable region (abbreviated herein as V H ) and a heavy chain constant (C H ) region. The heavy chain constant region is comprised of three domains, CH1, CH2 and CH3. Each light chain is comprised of a light chain variable region (abbreviated herein as V L ) and a light chain constant CL region. The light chain constant region is comprised of one domain, C L . The V H  and V L  regions can be further sub-divided into regions of hypervariability, termed complementarity determining regions (CDR), interspersed with regions that are more conserved, termed framework regions (FR). Each V H  and V L  is composed of three CDRs and four FRs arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The variable regions of the heavy and light chains contain a binding domain that interacts with an antigen. The constant regions of the antibodies may mediate the binding of the immunoglobulin to host tissues or factors, including various cells of the immune system (e.g., effector cells) and the first component (C1 q) of the classical complement system. 
     As used herein, the term “single-chain variable fragment” or “scFv” is a fusion protein of the variable regions of the heavy (V H ) and light chains (V L ) of an immunoglobulin (e.g., mouse or human) covalently linked to form a V H ::V L  heterodimer. The heavy (V H ) and light chains (V L ) are either joined directly or joined by a peptide-encoding linker (e.g., about 10, 15, 20, 25 amino acids), which connects the N-terminus of the V H  with the C-terminus of the V L , or the C-terminus of the V H  with the N-terminus of the V L . 
     As used herein, a “linker” refers to a functional group (e.g., chemical or polypeptide) that covalently attaches two or more polypeptides or nucleic acids so that they are connected to one another. In certain embodiments, the linker comprises one or more amino acids used to couple two proteins together (e.g., to couple V H  and V L  domains or to couple two dimerization domains). The linker can be usually rich in glycine for flexibility, as well as serine or threonine for solubility. 
     As used herein, the term “vector” refers to any genetic element, such as a plasmid, phage, transposon, cosmid, chromosome, virus, virion, etc., which is capable of replication when associated with the proper control elements and which can transfer gene sequences into cells. Thus, the term includes cloning and expression vectors, including viral vectors and plasmid vectors. 
     As used herein, the term “expression vector” refers to a recombinant nucleic acid sequence, e.g., a recombinant DNA molecule, containing a desired coding sequence operably linked to appropriate nucleic acid sequences necessary for the expression of the coding sequence in a particular host organism. Nucleic acid sequences necessary for expression in prokaryotes usually include a promoter, an operator (optional), and a ribosome binding site, often along with other sequences. Nucleic acid sequences necessary for expression in eukaryotic cells can include, but are not limited to. 
     In certain embodiments, nucleic acid molecules useful in the presently disclosed subject matter include nucleic acid molecules that encode an antibody or an antigen-binding fragment thereof. Such nucleic acid molecules need not be 100% identical with an endogenous nucleic acid sequence, but will typically exhibit substantial identity. Polynucleotides having “substantial homology” or “substantial identity” to an endogenous sequence are typically capable of hybridizing with at least one strand of a double-stranded nucleic acid molecule. 
     As used herein, the term “disease” refers to any condition or disorder that damages or interferes with the normal function of a cell, tissue, or organ. Examples of diseases include neoplasia or pathogenic infection of a cell, tissue, or organ. 
     An “effective amount” (or “therapeutically effective amount”) is an amount sufficient to effect a beneficial or desired clinical result upon treatment. An effective amount can be administered to a subject in one or more doses. In terms of treatment, an effective amount is an amount that is sufficient to palliate, ameliorate, stabilize, reverse or slow the progression of the disease (e.g., a neoplasia), or otherwise reduce the pathological consequences of the disease (e.g., a neoplasia). The dose comprising an effective amount is generally determined by the physician on a case-by-case basis and making such a determination is within the level of ordinary skill in the art. Several factors are typically taken into account when determining an appropriate dosage to achieve an effective amount. These factors include age, sex and weight of the subject, the condition being treated, the severity of the condition and the form and effective concentration of the cells (e.g., engineered immune cells) administered. 
     As used herein, the term “neoplasm” refers to a disease characterized by the pathological proliferation of a cell or tissue and its subsequent migration to or invasion of other tissues or organs. Neoplasia growth is typically uncontrolled and progressive, and occurs under conditions that would not elicit, or would cause cessation of, multiplication of normal cells. Neoplasia can affect a variety of cell types, tissues, or organs, including but not limited to an organ selected from the group consisting of skin, bladder, colon, bone, brain, breast, cartilage, glia, esophagus, fallopian tube, gallbladder, heart, intestines, kidney, liver, lung, lymph node, nervous tissue, ovaries, pleura, pancreas, prostate, skeletal muscle, spinal cord, spleen, stomach, testes, thymus, thyroid, trachea, urogenital tract, ureter, urethra, uterus, and vagina, or a tissue or cell type thereof. Neoplasia include cancers, such as melanoma, sarcomas, carcinomas, or plasmacytomas (malignant tumor of the plasma cells). 
     As used herein, the term “immunoresponsive cell” refers to a cell that functions in an immune response, and includes a progenitor of such cell, or a progeny of such cell. 
     As used herein, the term “isolated cell” refers to a cell that is separated from the molecular and/or cellular components that naturally accompany the cell. 
     As used herein, the term “isolated,” “purified,” or “biologically pure” refers to material that is free to varying degrees from components which normally accompany it as found in its native state. “Isolate” denotes a degree of separation from original source or surroundings. “Purify” denotes a degree of separation that is higher than isolation. A “purified” or “biologically pure” protein is sufficiently free of other materials such that any impurities do not materially affect the biological properties of the protein or cause other adverse consequences. That is, a nucleic acid or polypeptide of the presently disclosed subject matter is purified if it is substantially free of cellular material, viral material, or culture medium when produced by recombinant DNA techniques, or chemical precursors or other chemicals when chemically synthesized. Purity and homogeneity are typically determined using analytical chemistry techniques, for example, polyacrylamide gel electrophoresis or high performance liquid chromatography. The term “purified” can denote that a nucleic acid or protein gives rise to essentially one band in an electrophoretic gel. For a protein that can be subjected to modifications, for example, phosphorylation or glycosylation, different modifications may give rise to different isolated proteins, which can be separately purified. 
     As used herein, the term “secreted” refers to a polypeptide that is released from a cell via the secretory pathway through the endoplasmic reticulum, Golgi apparatus, and as a vesicle that transiently fuses at the cell plasma membrane, releasing the proteins outside of the cell. 
     As used herein, the term “treating” or “treatment” refers to clinical intervention in an attempt to alter the disease course of the individual or cell being treated, and can be performed either for prophylaxis or during the course of clinical pathology. Therapeutic effects of treatment include, without limitation, preventing occurrence or recurrence of disease, alleviation of symptoms, diminishment of any direct or indirect pathological consequences of the disease, preventing metastases, decreasing the rate of disease progression, amelioration or palliation of the disease state, and remission or improved prognosis. By preventing progression of a disease or disorder, a treatment can prevent deterioration due to a disorder in an affected or diagnosed subject or a subject suspected of having the disorder, but also a treatment may prevent the onset of the disorder or a symptom of the disorder in a subject at risk for the disorder or suspected of having the disorder. 
     As used herein, the term “subject” refers to any animal (e.g., a mammal), including, but not limited to, humans, non-human primates, rodents, and the like (e.g., which is to be the recipient of a particular treatment). 
     The term “chimeric antigen receptor” or “CAR” as used herein refers to a molecule comprising an extracellular antigen-binding domain that is fused to an intracellular signaling domain that is capable of activating or stimulating an immunoresponsive cell, and a transmembrane domain. In certain embodiments, the extracellular antigen-binding domain of a CAR comprises a scFv. The scFv can be derived from fusing the variable heavy and light regions of an antibody. Alternatively or additionally, the scFv may be derived from Fab&#39;s (instead of from an antibody, e.g., obtained from Fab libraries). In certain embodiments, the scFv is fused to the transmembrane domain and then to the intracellular signaling domain. In certain embodiments, the CAR is selected to have high binding affinity or avidity for the antigen. 
     In certain non-limiting embodiments, an intracellular signaling domain of a CAR or a ZipR-CAR comprises a CD3ζ polypeptide, which can activate or stimulate a cell (e.g., a cell of the lymphoid lineage, e.g., a T cell). CD3ζ comprises 3 immunoreceptor tyrosine-based activation motifs (ITAMs), and transmits an activation signal to the cell (e.g., a cell of the lymphoid lineage, e.g., a T cell) after antigen is bound. The intracellular signaling domain of the CD3ζ-chain is the primary transmitter of signals from endogenous TCRs. 
     In certain non-limiting embodiments, a CAR or a ZipR-CAR can also comprise a spacer/hinge region that links the extracellular antigen-binding domain to the transmembrane domain. The spacer region can be flexible enough to allow the antigen binding domain to orient in different directions to facilitate antigen recognition. The spacer region can be the hinge region from IgG1, or the CH 2 CH 3  region of immunoglobulin and fragments of CD3, a fragment of a CD28 polypeptide, a fragment of a CD8 polypeptide, a variant thereof, or a synthetic spacer sequence. 
     As used herein, “costimulatory molecules” refer to cell surface molecules other than antigen receptors or their ligands that are required for a response of lymphocytes to antigen. The at least one co-stimulatory signaling region can include a CD28 polypeptide (e.g., intracellular domain of CD28 or a fragment thereof), a 4-1BB polypeptide (e.g., intracellular domain of 4-1BB or a fragment thereof), an OX40 polypeptide (e.g., intracellular domain of OX40 or a fragment thereof), an ICOS polypeptide (e.g., intracellular domain of ICOS or a fragment thereof), a DAP-10 polypeptide (e.g., intracellular domain of DAP-10 or a fragment thereof), or a combination thereof. As used herein, the term a “co-stimulatory ligand” refers to a protein expressed on cell surface that upon binding to its receptor produces a co-stimulatory response, i.e., an intracellular response that effects the stimulation provided by an activating signaling domain (e.g., a CD3ζ signaling domain). Non-limiting examples of co-stimulatory ligands include tumor necrosis factor (TNF) family members, immunoglobulin (Ig) superfamily members, or combination thereof the co-stimulatory ligand is selected from the group consisting of tumor necrosis factor (TNF) family members, immunoglobulin (Ig) superfamily members, and combinations thereof. Non-limiting examples of TNF family member include 4-1BBL, OX40L, CD70, GITRL, CD40L, and CD30L. Non-limiting examples of Ig superfamily member include CD80, CD86, and ICOSLG. For example, 4-1BBL may bind to 4-1BB for providing an intracellular signal that in combination with a CAR signal induces an effector cell function of the CAR +  T cell. CARs comprising an intracellular signaling domain that comprises a co-stimulatory signaling region comprising a 4-1BB, ICOS or DAP-10 co-stimulatory signaling domain are disclosed in U.S. Pat. No. 7,446,190, which is herein incorporated by reference in its entirety. 
     As used herein, the term “multimerization” refers to the formation of multimers (including dimers). Multimerization includes dimerization. 
     As used herein, the term “a conservative sequence modification” refers to an amino acid modification that does not significantly affect or alter the binding characteristics of the presently disclosed polypeptide (e.g., the extracellular antigen-binding domain of the polypeptide) comprising the amino acid sequence. Conservative modifications can include amino acid substitutions, additions and deletions. Modifications can be introduced into the human scFv of the presently disclosed polypeptide by standard techniques known in the art, such as site-directed mutagenesis and PCR-mediated mutagenesis. Amino acids can be classified into groups according to their physicochemical properties such as charge and polarity. Conservative amino acid substitutions are ones in which the amino acid residue is replaced with an amino acid within the same group. For example, amino acids can be classified by charge: positively-charged amino acids include lysine, arginine, histidine, negatively-charged amino acids include aspartic acid, glutamic acid, neutral charge amino acids include alanine, asparagine, cysteine, glutamine, glycine, isoleucine, leucine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine. In addition, amino acids can be classified by polarity: polar amino acids include arginine (basic polar), asparagine, aspartic acid (acidic polar), glutamic acid (acidic polar), glutamine, histidine (basic polar), lysine (basic polar), serine, threonine, and tyrosine; non-polar amino acids include alanine, cysteine, glycine, isoleucine, leucine, methionine, phenylalanine, proline, tryptophan, and valine. Thus, one or more amino acid residues within a CDR region can be replaced with other amino acid residues from the same group and the altered antibody can be tested for retained function (i.e., the functions set forth in (c) through (1) above) using the functional assays described herein. In certain embodiments, no more than one, no more than two, no more than three, no more than four, no more than five residues within a specified sequence or a CDR region are altered. 
     As used herein, the percent homology between two amino acid sequences is equivalent to the percent identity between the two sequences. The percent identity between the two sequences is a function of the number of identical positions shared by the sequences (i.e., % homology=# of identical positions/total # of positions×100), taking into account the number of gaps, and the length of each gap, which need to be introduced for optimal alignment of the two sequences. The comparison of sequences and determination of percent identity between two sequences can be accomplished using a mathematical algorithm. 
     The percent homology between two amino acid sequences can be determined using the algorithm of E. Meyers and W. Miller (Comput. Appl. Biosci., 4:11-17 (1988)) which has been incorporated into the ALIGN program (version 2.0), using a PAM120 weight residue table, a gap length penalty of 12 and a gap penalty of 4. In addition, the percent homology between two amino acid sequences can be determined using the Needleman and Wunsch (J. Mol. Biol. 48:444-453 (1970)) algorithm which has been incorporated into the GAP program in the GCG software package (available at www.gcg.com), using either a Blossum 62 matrix or a PAM250 matrix, and a gap weight of 16, 14, 12, 10, 8, 6, or 4 and a length weight of 1, 2, 3, 4, 5, or 6. 
     Additionally or alternatively, the amino acids sequences of the presently disclosed subject matter can further be used as a “query sequence” to perform a search against public databases to, for example, identify related sequences. Such searches can be performed using the)(BLAST program (version 2.0) of Altschul, et al. (1990) J. Mol. Biol. 215:403-10. BLAST protein searches can be performed with the XBLAST program, score=50, wordlength=3 to obtain amino acid sequences homologous to the specified sequences (e.g., heavy and light chain variable region sequences of scFv m903, m904, m905, m906, and m900) disclosed herein. To obtain gapped alignments for comparison purposes, Gapped BLAST can be utilized as described in Altschul et al., (1997) Nucleic Acids Res. 25(17):3389-3402. When utilizing BLAST and Gapped BLAST programs, the default parameters of the respective programs (e.g.,)(BLAST and NBLAST) can be used. 
     2. Membrane-Bound Polypeptide and Soluble Polypeptides 
     The presently disclosed subject matter provides systems and methods comprising a membrane-bound polypeptide and a soluble polypeptide, wherein the soluble polypeptide is capable of dimerizing with the membrane-bound polypeptide. 
     2.1 Membrane-Bound Polypeptide 
     In certain embodiments, the membrane-bound polypeptide comprises a transmembrane domain and an extracellular domain. In certain embodiments, the membrane-bound polypeptide further comprises a hinge/spacer domain and/or an intracellular domain. 
     2.1.1. Extracellular Domain 
     In certain embodiments, the extracellular domain of the membrane-bound polypeptide comprises a dimerization domain. The dimerization domain comprises a leucine zipper domain. In certain embodiments, the dimerization domain is capable of dimerizing with one or more dimerization domain comprised in the membrane-bound polypeptide. In certain embodiments, the dimerization domain is capable of dimerizing with one or more dimerization domain comprised in a soluble polypeptide disclosed herein. 
     In certain embodiments, the extracellular domain of the membrane-bound polypeptide comprises a first dimerization domain and a second dimerization domain that is capable of dimerizing with the first dimerization domain at a cell surface. In certain embodiments, the first dimerization domain comprises a first leucine zipper domain. In certain embodiments, the second dimerization domain comprises a second leucine zipper domain. 
     In certain embodiments, the leucine zipper domain comprises a dimerization domain of the Basic-region leucine zipper (bZIP) class of eukaryotic transcription factors. In certain embodiments, the leucine zipper domain comprises a specific alpha helix monomer that can dimerize with anther alpha helix monomer. In certain embodiments, the leucine zipper domain comprises an EE domain that comprises one or more acidic amino acids, e.g., glutamic acid (E). In certain embodiments, the leucine zipper domain comprises an RR domain that comprises one or more basic amino acids, e.g., arginine (R). In certain embodiments, the first leucine zipper domain comprises an RR domain and the second leucine zipper domain comprises an EE domain. 
     In certain embodiments, the RR domain comprises an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the amino acid sequence set forth in SEQ ID NO: 1 or a fragment thereof. In certain embodiments, the RR domain comprises a modification of SEQ ID NO: 1 or a fragment thereof. In certain embodiments, the modification comprises up to one, up to two, or up to three amino acid substitutions. SEQ ID NO: 1 is provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 1] 
               
               
                 LEIRAAFLRQRNTALRTEVAELEQEVQRLENEVSQYETRYGPL GGGK 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 1 is set forth in SEQ ID NO: 58, which is provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 58] 
               
               
                 CTGGAGATCCGCGCTGCATTTTTGCGACAAAGAAATACCGCTTTGCGAAC 
               
               
                   
               
               
                 CGAAGTGGCCGAGTTGGAGCAGGAAGTACAACGCCTGGAAAATGAAGTCA 
               
               
                   
               
               
                 GCCAATACGAAACTCGATATGGACCTCTCGGAGGTGGAAAG 
               
            
           
         
       
     
     In certain embodiments, the RR domain comprises a modification of SEQ ID NO: 1, wherein the modification consists of or has one amino acid substitution. In certain embodiments, the RR domain comprises the amino acid sequence set forth in SEQ ID NO: 59 or SEQ ID NO: 60. SEQ ID NO: 59 and SEQ ID NO: 60 are provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 59] 
               
               
                 LEIEAAFLRQRNTALRTEVAELEQEVQRLENEVSQYETRYGPLGGGK 
               
               
                   
               
               
                 [SEQ ID NO: 60] 
               
               
                 LEIRAAFLRQRNTALRTRVAELEQEVQRLENEVSQYETRYGPLGGGK 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 59 is set forth in SEQ ID NO: 61, which is provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 61] 
               
               
                 CTGGAGATCGAAGCTGCATTTTTGCGACAAAGAAATACCGCTTTGCGAAC 
               
               
                   
               
               
                 CGAAGTGGCCGAGTTGGAGCAGGAAGTACAACGCCTGGAAAATGAAGTCA 
               
               
                   
               
               
                 GCCAATACGAAACTCGATATGGACCTCTCGGAGGTGGAAAG 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 60 is set forth in SEQ ID NO: 62, which is provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 62] 
               
               
                 CTGGAGATCCGCGCTGCATTTTTGCGACAAAGAAATACCGCTTTGCGAAC 
               
               
                   
               
               
                 CCGCGTGGCCGAGTTGGAGCAGGAAGTACAACGCCTGGAAAATGAAGTCA 
               
               
                   
               
               
                 GCCAATACGAAACTCGATATGGACCTCTCGGAGGTGGAAAG 
               
            
           
         
       
     
     In certain embodiments, the RR domain comprises a modification of SEQ ID NO: 1, wherein the modification consists of or has two amino acid substitutions. In certain embodiments, the RR domain comprises the amino acid sequence set forth in SEQ ID NO: 63 or SEQ ID NO: 64. SEQ ID NO: 63 and SEQ ID NO: 64 are provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 63] 
               
               
                 LEIEAAFLRQENTALRTEVAELEQEVQRLENEVSQYETRYGPLGGGK 
               
               
                   
               
               
                 [SEQ ID NO: 64] 
               
               
                 LEIRAAFLRQRNTALRTRVAELEQRVQRLENEVSQYETRYGPLGGGK 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 63 is set forth in SEQ ID NO: 65, which is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 65] 
               
               
                   
                 CTGGAGATCGAAGCTGCATTTTTGCGACAAGAAAATACCG 
               
               
                   
               
               
                   
                 CTTTGCGAACCGAAGTGGCCGAGTTGGAGCAGGAAGTACA 
               
               
                   
               
               
                   
                 ACGCCTGGAAAATGAAGTCAGCCAATACGAAACTCGATAT 
               
               
                   
               
               
                   
                 GGACCTCTCGGAGGTGGAAAG 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 64 is set forth in SEQ ID NO: 66, which is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 66] 
               
               
                   
                 CTGGAGATCCGCGCTGCATTTTTGCGACAAAGAAATACCG 
               
               
                   
               
               
                   
                 CTTTGCGAACCCGCGTGGCCGAGTTGGAGCAGCGCGTACA 
               
               
                   
               
               
                   
                 ACGCCTGGAAAATGAAGTCAGCCAATACGAAACTCGATAT 
               
               
                   
               
               
                   
                 GGACCTCTCGGAGGTGGAAAG 
               
            
           
         
       
     
     In certain embodiments, the RR domain comprises a modification of SEQ ID NO: 1, wherein the modification consists of or has three amino acid substitutions. In certain embodiments, the RR domain comprises the amino acid sequence set forth in SEQ ID NO: 67 or SEQ ID NO: 68. SEQ ID NO: 67 and SEQ ID NO: 68 are provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 67] 
               
               
                 LEIEAAFLRQENTALRTRVAELEQEVQRLENEVSQYETRYGPLGGGK 
               
               
                   
               
               
                 [SEQ ID NO: 68] 
               
               
                 LEIRAAFLRQRNTALRTRVAELEQRVQRLENRVSQYETRYGPLGGGK 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 67 is set forth in SEQ ID NO: 69, which is provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 69] 
               
               
                 CTGGAGATCGAAGCTGCATTTTTGCGACAAGAAAATACCGCTTTGCG 
               
               
                   
               
               
                 AACCCGAGTGGCCGAGTTGGAGCAGGAAGTACAACGCCTGGAAAATG 
               
               
                   
               
               
                 AAGTCAGCCAATACGAAACTCGATATGGACCTCTCGGAGGTGGAAAG 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 68 is set forth in SEQ ID NO: 70, which is provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 70] 
               
               
                 CTGGAGATCCGCGCTGCATTTTTGCGACAAAGAAATACCGCTTTGCGA 
               
               
                   
               
               
                 ACCCGAGTGGCCGAGTTGGAGCAGCGAGTACAACGCCTGGAAAATCGA 
               
               
                   
               
               
                 GTCAGCCAATACGAAACTCGATATGGACCTCTCGGAGGTGGAAAG 
               
            
           
         
       
     
     In certain embodiment, the modification is positioned in the “g” residues of the RR domain of the leucine zipper. In certain embodiment, the modification reduces heterodimerization affinity between the membrane-bound polypeptide and a linked soluble polypeptide. 
     In certain embodiments, the EE domain comprises an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the amino acid sequence set forth in SEQ ID NO: 2 or a fragment thereof. In certain embodiments, the EE domain comprises a modification of SEQ ID NO: 2 or a fragment thereof. In certain embodiments, the modification comprises up to one, up to two, or up to three amino acid substitutions. SEQ ID NO: 2 is provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 2] 
               
               
                 LEIEAAFLERENTALETRVAELRQRVQRLRNRVSQYRTRYGPLGGGK 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 2 is set forth in SEQ ID NO: 71, which is provided below. 
     
       
         
           
               
            
               
                 [SEQ ID NO: 71] 
               
               
                 CTGGAGATTGAGGCTGCATTTCTTGAAAGAGAAAACACTGCTCTTGAG 
               
               
                   
               
               
                 ACAAGAGTCGCCGAACTGAGGCAGCGCGTTCAGCGCCTGCGGAACCGA 
               
               
                   
               
               
                 GTATCTCAATACAGGACTCGGTACGGACCACTGGGGGGCGGTAAG 
               
            
           
         
       
     
     In certain embodiments, the extracellular domain further comprises a linker between the first dimerization domain and the second dimerization domain. In certain embodiments, the linker comprises the amino acid sequence set forth in SEQ ID NO: 3 or SEQ ID NO: 20. SEQ ID Nos: 3 and 20 are provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 3] 
               
               
                   
                 GGGGSGGGGSGGGGSGGGS 
               
               
                   
               
               
                   
                 [SEQ ID NO: 20] 
               
               
                   
                 GGGGSGGGGSGGGGS 
               
            
           
         
       
     
     In certain embodiments, a dimerization domain comprises an orthogonal zipper. Orthogonal zippers are coiled coil domains that form heterodimers with their specific partner only and not with other zipper domains. In certain embodiments, orthogonality refers to sets of molecules (e.g., leucine zippers) that are non-cross-reactive, i.e., “orthogonal”, to other sets of molecules. For example, A+B=AB and C+D=CD, but neither A nor B bind to C or D, and vice versa. 
     In certain embodiments, the first and second leucine zipper domains of the membrane-bound polypeptide are a pair of orthogonal zippers i.e., the first and the second leucine zipper domains are the specific partners for each other to form heterodimers. Orthogonal zippers include, but are not limited to, RR/EE zippers, Fos/Jun zippers and Fos/synZip zippers. Fos/Jun zippers are previously disclosed in Ransone et al.,  Genes Dev.  1989 June; 3(6):770-81; Kohler et al., Biochemistry. (2001 January); 9; 40(1):130-42, which are incorporated by reference herein. Fos/synZip zippers are previously disclosed in Grigoryan et al.,  Nature . (2009); 458, 859-864; Reinke et al.,  J Am Chem Soc . (2010); 132, 6025-6031, which are incorporated by reference herein. 
     In certain embodiments, the orthogonal zippers comprise an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to RR/EE zippers, Fos/Jun zippers or Fos/synZip zippers, or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. 
     Examples of synZip-9, Fos and Jun zippers are set forth in SEQ ID NOs: 4, 5 and 6, respectively. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 4] 
               
               
                   
                 GSQKVESLKQKIEELKQRKAQLKNDIANLEKEIAYAET 
               
               
                   
               
               
                   
                 [SEQ ID NO: 5] 
               
               
                   
                 GSELTDTLQAETDQLEDEKSALQTEIANLLKEKEKLEFILAAHR 
               
               
                   
               
               
                   
                 [SEQ ID NO: 6] 
               
               
                   
                 ERISRLEEKVKTLKSQNTELASTASLLREQVAQLKQKVLSHVLE 
               
            
           
         
       
     
     In certain embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a spacer/hinge domain between a dimerization domain and a transmembrane domain. 
     In certain embodiments, the spacer/hinge domain is flexible enough to allow the dimerization domain to orient in different directions to facilitate antigen recognition after dimerizing with the soluble polypeptide disclosed herein. The spacer region can be the hinge region from IgG1, or the CH 2 CH 3  region of immunoglobulin and fragments of CD3, a fragment of a CD28 polypeptide, a fragment of a CD8 polypeptide, a variation of any of the foregoing that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% identical thereto, or a synthetic spacer sequence. 
     In certain embodiments, the spacer/hinge domain comprises an epitope recognized by an antibody. In certain embodiments, binding of the antibody to the epitope mediates a deletion of a cell comprising the membrane-bound polypeptide. In certain embodiments, the spacer/hinge domain comprises a Thy1.1 molecule, a truncated EGFR molecule (EGFRt), CD22 immunoglobulin-like domain epitope, an IgG/Fc domain (can be a Fc from any IgG), CD2, CD20 cyclic mimotope, CD30, CD52, or HER2. 
     In certain embodiments, the Thy1.1 molecule comprises or has the amino acid sequence set forth in SEQ ID NO: 95. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 95] 
               
               
                   
                 QKVTSLTACLVDQSLRLDCRHENTSSSPIQYEFSLTRETKKHVL 
               
               
                   
               
               
                   
                 FGTVGVPEHTYRSRTNFTSKYNMKVLYLSAFTSKDEGTYTCALH 
               
               
                   
               
               
                   
                 HSGHSPPISSQNVTVLRDKLVKC 
               
            
           
         
       
     
     In certain embodiments, the EGFRt comprises or has the amino acid sequence set forth in SEQ ID NO: 96. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 96] 
               
               
                   
                 RKVCNGIGIGEFKDSLSINATNIKHFKNCTSISGDLHILPVAFRG 
               
               
                   
               
               
                   
                 DSFTHIPPLDPQELDILKTVKEITGFLLIQAWPENRIDLHAFENL 
               
               
                   
               
               
                   
                 EIIRGRIKQHGQFSLAVVSLNITSLGLRSLKEISDGDVIISGNKN 
               
               
                   
               
               
                   
                 LCYANTINWKKLFGTSGQKTKIISNRGENSCKATGQVCHALCSPE 
               
               
                   
               
               
                   
                 GCWGPEPRDCVSCRNVSRGRECVDKCNLLEGEPREFVENSECIQC 
               
               
                   
               
               
                   
                 HPECLPQAMNITCTGRGPDNCIQCAHYIDGPHCVKTCPAGVMGEN 
               
               
                   
               
               
                   
                 NTLVWKYADAGHVCHLCHPNCTYGCTGPGLEGCPINGPKIPS 
               
            
           
         
       
     
     In certain embodiments, the membrane-bound polypeptide further comprises a blocking spacer, wherein the blocking spacer is capable of preventing dimerization of the membrane-bound polypeptide with a soluble polypeptide when the membrane-bound polypeptide and the soluble polypeptide are not expressed from the same cell. In certain embodiments, the blocking spacer comprises a minimum spacer of no more than about 20 to about 30 amino acid residues. In certain embodiments, the blocking spacer comprises no more than about 25 amino acid residues. In certain embodiments, the blocking spacer comprises about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9 about 10, about 11, about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19 or about 20 amino acid residues. In certain embodiments, the blocking spacer comprises between about 5 amino acid residues and about 25 amino acid residues, between about 5 amino acid residues and about 20 amino acid residues, between about 10 amino acid residues and about 25 amino acid residues or between about 10 amino acid residues and about 20 amino acid residues. 
     In certain embodiments, the blocking spacer comprises an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to a truncated CD28 spacer set forth in SEQ ID NO: 7 or 21, or a fragment thereof. In certain embodiments, the blocking spacer comprises an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous to an IgG1 hinge set forth in SEQ ID NO: 8 or SEQ ID NO: 22, or a fragment thereof. In certain embodiments, the blocking spacer comprises a modification of SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 21, and SEQ ID NO: 22, wherein the modification comprises up to one, up to two, or up to three amino acid substitutions. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 7] 
               
               
                   
                 CHTQSSPKL 
               
               
                   
               
               
                   
                 [SEQ ID NO: 8] 
               
               
                   
                 VPRDCGCKPCICT 
               
               
                   
               
               
                   
                 [SEQ ID NO: 21] 
               
               
                   
                 CPSPLFPGPSKP 
               
               
                   
               
               
                   
                 [SEQ ID NO: 22] 
               
               
                   
                 EPKSCDKTHTCPPC 
               
            
           
         
       
     
     In certain embodiments, the blocking spacer has a length of no more than about 25 amino acids. In certain embodiments, the blocking spacer has a length of between about 5 amino acids and about 25 amino acids. In certain embodiments, the blocking spacer is a truncated CD28 spacer or an IgG1 hinge. 
     In certain non-limiting embodiments, the extracellular domain of the membrane-bound polypeptide comprises at least one co-stimulatory ligand or a fragment thereof. Non-limiting examples of co-stimulatory ligands include tumor necrosis factor (TNF) family members, immunoglobulin (Ig) superfamily members, and a combination thereof. In certain embodiments, the co-stimulatory ligand is selected from the group consisting of tumor necrosis factor (TNF) family members, immunoglobulin (Ig) superfamily members, and combinations thereof. In certain embodiments, the TNF family member is selected from the group consisting of 4-1BBL, OX40L, CD70, GITRL, CD40L, and CD30L. 
     In certain embodiments, the co-stimulatory ligand is CD30L. CD30L-expressing systems can target CD30 on T cell lymphoma and Hodgkin lymphoma. 
     In certain embodiments, the Ig superfamily member is selected from the group consisting of CD80, CD86, and ICOSLG. 
     In certain embodiments, the co-stimulatory ligand is CD80. In certain embodiments, the CD80 is a mouse CD80. In certain embodiments, the CD80 comprises the amino acid sequence set forth in SEQ ID NO: 72. In certain embodiments, the CD80 is a human CD80. In certain embodiments, the CD80 comprises the amino acid sequence set forth in SEQ ID NO: 73. SEQ ID Nos: 72 and 73 are provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 72] 
               
               
                   
                 VDEQLSKSVKDKVLLPCRYNSPHEDESEDRIYWQKHDKVV 
               
               
                   
               
               
                   
                 LSVIAGKLKVWPEYKNRTLYDNTTYSLIILGLVLSDRGTY 
               
               
                   
               
               
                   
                 SCVVQKKERGTYEVKHLALVKLSIKADFSTPNITESGNPS 
               
               
                   
               
               
                   
                 ADTKRITCFASGGFPKPRFSWLENGRELPGINTTISQDPE 
               
               
                   
               
               
                   
                 SELYTISSQLDFNTTRNHTIKCLIKYGDAHVSEDFTWEKP 
               
               
                   
               
               
                   
                 PEDPPDSKNTLVLFGAGFGAVITVVVIVVIIKCFCKHRSC 
               
               
                   
               
               
                   
                 FRRNEASRETNNSLTFGPEEALAEQTVFL 
               
               
                   
               
               
                   
                 [SEQ ID NO: 73] 
               
               
                   
                 VIHVTKEVKEVATLSCGHNVSVEELAQTRIYWQKEKKMVL 
               
               
                   
               
               
                   
                 TMMSGDMNIWPEYKNRTIFDITNNLSIVILALRPSDEGTY 
               
               
                   
               
               
                   
                 ECVVLKYEKDAFKREHLAEVTLSVKADEPTPSISDFEIPT 
               
               
                   
               
               
                   
                 SNIRRIICSTSGGFPEPHLSWLENGEELNAINTTVSQDPE 
               
               
                   
               
               
                   
                 TELYAVSSKLDFNMTTNHSFMCLIKYGHLRVNQTENWNTT 
               
               
                   
               
               
                   
                 KQEHFPDNLLPSWAITLISVNGIFVICCLTYCFAPRCRER 
               
               
                   
               
               
                   
                 RRNERLRRESVRPV 
               
            
           
         
       
     
     In certain embodiments, the co-stimulatory ligand is 4-1BBL. In certain embodiments, the 4-1BBL is a mouse 4-1BBL. In certain embodiments, the 4-1BBL comprises the amino acid sequence set forth in SEQ ID NO: 74. In certain embodiments, the 4-1BBL is a human 4-1BBL. In certain embodiments, the 4-1BBL comprises the amino acid sequence set forth in SEQ ID NO: 75. SEQ ID Nos: 74 and 75 are provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 74] 
               
               
                   
                 MDQHTLDVEDTADARHPAGTSCPSDAALLRDTGLLADAAL 
               
               
                   
               
               
                   
                 LSDTVRPTNAALPTDAAYPAVNVRDREAAWPPALNFCSRH 
               
               
                   
               
               
                   
                 PKLYGLVALVLLLLIAACVPIFTRTEPRPALTITTSPNLG 
               
               
                   
               
               
                   
                 TRENNADQVTPVSHIGCPNTTQQGSPVFAKLLAKNQASLC 
               
               
                   
               
               
                   
                 NTTLNWHSQDGAGSSYLSQGLRYEEDKKELVVDSPGLYYV 
               
               
                   
               
               
                   
                 FLELKLSPTFTNTGHKVQGWVSLVLQAKPQVDDFDNLALT 
               
               
                   
               
               
                   
                 VELFPCSMENKLVDRSWSQLLLLKAGHRLSVGLRAYLHGA 
               
               
                   
               
               
                   
                 QDAYRDWELSYPNTTSFGLFLVKPDNPWE 
               
               
                   
               
               
                   
                 [SEQ ID NO: 75] 
               
               
                   
                 MEYASDASLDPEAPWPPAPRARACRVLPWALVAGLLLLLL 
               
               
                   
               
               
                   
                 LAAACAVFLACPWAVSGARASPGSAASPRLREGPELSPDD 
               
               
                   
               
               
                   
                 PAGLLDLRQGMFAQLVAQNVLLIDGPLSWYSDPGLAGVSL 
               
               
                   
               
               
                   
                 TGGLSYKEDTKELVVAKAGVYYVFFQLELRRVVAGEGSGS 
               
               
                   
               
               
                   
                 VSLALHLQPLRSAAGAAALALTVDLPPASSEARNSAFGFQ 
               
               
                   
               
               
                   
                 GRLLHLSAGQRLGVHLHTEARARHAWQLTQGATVLGLFRV 
               
               
                   
               
               
                   
                 TPEIPAGLPSPRSE 
               
            
           
         
       
     
     In certain non-limiting embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a dominant negative molecule or a fragment thereof. In certain embodiments, the dominant negative molecule is selected from the group consisting of inhibitors of immune checkpoint molecules, tumor necrosis factor receptor superfamily (TNFRSF) members, and TGFβ receptors. In certain embodiment, the immune checkpoint molecule is selected from the group consisting of PD-1, CTLA-4, B7-H3, B7-H4, BTLA, TIM-3, LAG-3, TIGIT, LAIR1, CD200, CD200R, HVEM, 2B4, CD160, Galectin9, and combinations thereof. In certain embodiments, the immune checkpoint molecule is PD-1. In certain embodiments, the TNFRSF member is selected from the group consisting of Fas, a Tumor necrosis factor receptor, OX40, CD40, CD27, CD30, 4-1BB, and combinations thereof. In certain embodiments, the dominant negative receptor comprises an extracellular domain of TGFβRII or a fragment thereof. 
     In certain non-limiting embodiments, the dominant genitive molecule is an inhibitor of an immune checkpoint molecule. Details of dominant negative (DN) forms of inhibitors of an immune checkpoint molecule are disclosed in WO2017/040945 and WO2017/100428, the contents of each of which are incorporated by reference herein in their entireties. In certain embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a dominant negative form of an immune checkpoint inhibitor disclosed in WO2017/040945. In certain embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a dominant negative form of an immune checkpoint inhibitor disclosed in WO2017/100428. 
     In certain embodiments, the dominant negative molecule is a PD-1 dominant negative (i.e., PD-1 DN) molecule. In certain embodiments, the PD-1 DN comprises (a) at least a fragment of an extracellular domain of PD-1 comprising a ligand binding region, and (b) a transmembrane domain. 
     In certain embodiments, the PD-1 DN is a mouse PD-1 DN. In certain embodiments, the PD-1 DN comprises or has the amino acid sequence set forth in SEQ ID NO: 76, which is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 76] 
               
               
                   
                 LEVPNGPWRSLTFYPAWLTVSEGANATFTCSLSNWSEDLM 
               
               
                   
               
               
                   
                 LNWNRLSPSNQTEKQAAFCNGLSQPVQDARFQIIQLPNRH 
               
               
                   
               
               
                   
                 DFHMNILDTRRNDSGIYLCGAISLHPKAKIEESPGAELVV 
               
               
                   
               
               
                   
                 TERILETSTRYPSPSPKPEGRFQGM 
               
            
           
         
       
     
     In certain embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a tag. In certain embodiments, the tag comprises an epitope tag recognized by a first antibody. Non-limiting examples of epitope tags include Myc-tag, a HA-tag, a Flag-tag, a V5-tag, and a T7-tag. 
     In certain embodiments, the tag comprises an affinity tag that binds to a substrate. Non-limiting examples of affinity tags include a His-tag, a Strep-tag, an E-tag, and a streptavidin binding protein tag (SBP-tag). 
     Furthermore, the extracellular domain of the membrane-bound polypeptide can further comprise a mimotope recognized by a second antibody. Binding of the second antibody to the mimotope can mediates depletion of a cell comprising the membrane-bound polypeptide. In certain embodiments, the mimotope is a CD20 mimotope recognized by an anti-CD20 antibody. In certain embodiments, the anti-CD20 antibody is Rituxumab. In certain embodiments, the CD20 mimotope is a circular CD20 mimotope. 
     In certain embodiments, the CD20 mimotope comprises or has the amino acid sequence set forth in SEQ ID NO: 77, which is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 77] 
               
               
                   
                 CPYSNPSLC 
               
            
           
         
       
     
     2.1.2. Transmembrane Domain 
     Different transmembrane domains can result in different receptor stabilities. In accordance with the presently disclosed subject matter, the transmembrane domain can comprise a CD8 polypeptide (e.g., the transmembrane domain of CD8 or a fragment thereof), a CD28 polypeptide (e.g., the transmembrane domain of CD28 or a fragment thereof), a CD3ζ polypeptide (e.g., the transmembrane domain of CD3ζ or a fragment thereof), a CD4 polypeptide (e.g., the transmembrane domain of CD4 or a fragment thereof), a 4-1BB polypeptide (e.g., the transmembrane domain of 4-1BB or a fragment thereof), an OX40 polypeptide (e.g., the transmembrane domain of OX40 or a fragment thereof), an ICOS polypeptide (e.g., the transmembrane domain of ICOS or a fragment thereof), a CD2 polypeptide (e.g., the transmembrane domain of CD2 or a fragment thereof), a synthetic peptide (not based on a protein associated with the immune response), or a combination thereof. 
     In certain embodiments, the transmembrane domain of the membrane-bound polypeptide comprises a CD8 polypeptide (e.g., the transmembrane domain of CD8 or a fragment thereof). In certain embodiments, the CD8 polypeptide comprises or has an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: NP_001139345.1 (SEQ ID NO: 9) or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. In certain embodiments, the CD8 polypeptide comprises or has an amino acid sequence that is a consecutive fragment of SEQ ID NO: 9 which is at least 20, or at least 30, or at least 40, or at least 50, and up to 235 amino acids in length. Alternatively or additionally, in non-limiting various embodiments, the CD8 polypeptide comprises or has an amino acid sequence of amino acids 1 to 235, 1 to 50, 50 to 100, 100 to 150, 150 to 200, 183 to 203, or 200 to 235 of SEQ ID NO: 9. In certain embodiments, the transmembrane domain of the membrane-bound polypeptide comprises a CD8 polypeptide comprising or having an amino acid sequence of amino acids 183 to 203 of SEQ ID NO: 9. SEQ ID NO: 9 is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 9] 
               
               
                   
                 MALPVTALLLPLALLLHAARPSQFRVSPLDRTWNLGETVE 
               
               
                   
               
               
                   
                 LKCQVLLSNPTSGCSWLFQPRGAAASPTFLLYLSQNKPKA 
               
               
                   
               
               
                   
                 AEGLDTQRFSGKRLGDTFVLTLSDFRRENEGYYFCSALSN 
               
               
                   
               
               
                   
                 SIMYFSHFVPVFLPAKPTTTPAPRPPTPAPTIASQPLSLR 
               
               
                   
               
               
                   
                 PEACRPAAGGAVHTRGLDFACDIYIWAPLAGTCGVLLLSL 
               
               
                   
               
               
                   
                 VITLYCNHRNRRRVCKCPRPVVKSGDKPSLSARYV 
               
            
           
         
       
     
     In certain embodiments, the CD8 polypeptide comprises or has an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: AAA92533.1 (SEQ ID NO: 10) or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. In certain embodiments, the CD8 polypeptide comprises or has an amino acid sequence that is a consecutive fragment of SEQ ID NO: 10 which is at least about 20, or at least about 30, or at least about 40, or at least about 50, or at least about 60, or at least about 70, or at least about 100, or at least about 200, and up to 247 amino acids in length. Alternatively or additionally, in non-limiting various embodiments, the CD8 polypeptide comprises or has an amino acid sequence of amino acids 1 to 247, 1 to 50, 50 to 100, 100 to 150, 150 to 200, or 200 to 247 of SEQ ID NO: 10. SEQ ID NO: 10 is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 10] 
               
               
                   
                 MASPLTRFLSLNLLLMGESIILGSGEAKPQ 
               
               
                   
               
               
                   
                 APELRIFPKKMDAELGQKVDLVCEVLGSVS 
               
               
                   
               
               
                   
                 QGCSWLFQNSSSKLPQPTFVVYMASSHNKI 
               
               
                   
               
               
                   
                 TWDEKLNSSKLFSAVRDTNNKYVLTLNKFS 
               
               
                   
               
               
                   
                 KENEGYYFCSVISNSVMYFSSVVPVLQKVN 
               
               
                   
               
               
                   
                 STTTKPVLRTPSPVHPTGTSQPQRPEDCRP 
               
               
                   
               
               
                   
                 RGSVKGTGLDFACDIYIWAPLAGICVAPLL 
               
               
                   
               
               
                   
                 SLIITLICYHRSRKRVCKCPRPLVRQEGKP 
               
               
                   
               
               
                   
                 RPSEKIV 
               
            
           
         
       
     
     In certain embodiments, the CD8 polypeptide comprises or has the amino acid sequence set forth in SEQ ID NO: 11, which is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 11:] 
               
               
                   
                 IYIWAPLAGICVALLLSLIITLICY 
               
            
           
         
       
     
     In certain embodiments, the CD8 polypeptide comprises or has the amino acid sequence set forth in SEQ ID NO: 12, which is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 12:] 
               
               
                   
                 IYIWAPLAGTCGVLLLSLVIT 
               
            
           
         
       
     
     In certain embodiments, the transmembrane domain of the membrane-bound polypeptide comprises a CD28 polypeptide (e.g., the transmembrane domain of CD28 or a fragment thereof). The CD28 polypeptide can have an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: P10747 or NP_006130 (SEQ ID No: 14), or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. In certain embodiments, the CD28 polypeptide comprises or has an amino acid sequence that is a consecutive fragment of SEQ ID NO: 14 which is at least 20, or at least 30, or at least 40, or at least 50, and up to 220 amino acids in length. Alternatively or additionally, in non-limiting various embodiments, the CD28 polypeptide comprises or has an amino acid sequence of amino acids 1 to 220, 1 to 50, 50 to 100, 100 to 150, 114 to 220, 150 to 200, 153 to 179, or 200 to 220 of SEQ ID NO: 14. In certain embodiments, the transmembrane domain of a presently disclosed membrane-bound polypeptide comprises a CD28 polypeptide comprising or having an amino acid sequence of amino acids 153 to 179 of SEQ ID NO: 14. SEQ ID NO: 14 is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 14] 
               
               
                   
                 MLRLLLALNLFPSIQVTGNKILVKQSPMLV 
               
               
                   
               
               
                   
                 AYDNAVNLSCKYSYNLFSREFRASLHKGLD 
               
               
                   
               
               
                   
                 SAVEVCVVYGNYSQQLQVYSKTGFNCDGKL 
               
               
                   
               
               
                   
                 GNESVTFYLQNLYVNQTDIYFCKIEVMYPP 
               
               
                   
               
               
                   
                 PYLDNEKSNGTIIHVKGKHLCPSPLFPGPS 
               
               
                   
               
               
                   
                 KPFWVLVVVGGVLACYSLLVTVAFIIFWVR 
               
               
                   
               
               
                   
                 SKRSRLLHSDYMNMTPRRPGPTRKHYQPYA 
               
               
                   
               
               
                   
                 PPRDFAAYRS 
               
            
           
         
       
     
     In certain embodiments, the transmembrane domain of a membrane-bound polypeptide comprises a CD28 polypeptide comprising or having the amino acid sequence set forth in SEQ ID NO: 98 as provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 98] 
               
               
                   
                 FWVLVVVGGVLACYSLLVTVAFIIFWV 
               
            
           
         
       
     
     In certain embodiments, the transmembrane domain of a membrane-bound polypeptide comprises a CD28 polypeptide comprising or having the amino acid sequence set forth in SEQ ID NO: 23 as provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 23] 
               
               
                   
                 FWALVVVAGVLFCYGLLVTVALCVIWT 
               
            
           
         
       
     
     In certain embodiments, the transmembrane domain of the membrane-bound polypeptide comprises a CD4 polypeptide (e.g., the transmembrane domain of CD4 or a fragment thereof). The CD4 polypeptide can have an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: NP_038516.1 (SEQ ID NO: 78) or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. In certain embodiments, the CD4 polypeptide comprises or has an amino acid sequence that is a consecutive fragment of SEQ ID NO: 78 which is at least 20, or at least 30, or at least 40, or at least 50, and up to 457 amino acids in length. Alternatively or additionally, in non-limiting various embodiments, the CD4 polypeptide comprises or has an amino acid sequence of amino acids 1 to 457, 1 to 50, 50 to 100, 100 to 150, 150 to 200, 200 to 250, 250 to 300, 300 to 350, 350 to 400, 395 to 417, or 400 to 457 of SEQ ID NO: 78. In certain embodiments, the transmembrane domain of the membrane-bound polypeptide comprises a CD4 polypeptide comprising or having amino acids 395 to 417 of SEQ ID NO: 78. SEQ ID NO: 78 is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 78] 
               
               
                   
                 MCRAISLRRLLLLLLQLSQLLAVTQGKTLVLGKEGESAEL 
               
               
                   
               
               
                   
                 PCESSQKKITVETWKESDQRKILGQHGKGVLIRGGSPSQF 
               
               
                   
               
               
                   
                 DRFDSKKGAWEKGSFPLIINKLKMEDSQTYICELENRKEE 
               
               
                   
               
               
                   
                 VELWVFKVTFSPGTSLLQGQSLTLTLDSNSKVSNPLTECK 
               
               
                   
               
               
                   
                 HKKGKVVSGSKVLSMSNLRVQDSDFWNCTVTLDQKKNWFG 
               
               
                   
               
               
                   
                 MTLSVLGFQSTAITAYKSEGESAEFSFPLNFAEENGWGEL 
               
               
                   
               
               
                   
                 MWKAEKDSFFQPWISFSIKNKEVSVQKSTKDLKLQLKETL 
               
               
                   
               
               
                   
                 PLTLKIPQVSLQFAGSGNLTLTLDKGTLHQEVNLVVMKVA 
               
               
                   
               
               
                   
                 QLNNTLTCEVMGPTSPKMRLTLKQENQEARVSEEQKVVQV 
               
               
                   
               
               
                   
                 VAPETGLWQCLLSEGDKVKMDSRIQVLSRGVNQTVFLACV 
               
               
                   
               
               
                   
                 LGGSFGFLGFLGLCILCCVRCRHQQRQAARMSQIKRLLSE 
               
               
                   
               
               
                   
                 KKTCQCPHRMQKSHNLI 
               
            
           
         
       
     
     In certain embodiments, the transmembrane domain of the membrane-bound polypeptide comprises a CD4 polypeptide (e.g., the transmembrane domain of CD4 or a fragment thereof). The CD4 polypeptide can have an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: NP_000607.1 (SEQ ID No: 79) or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. In certain embodiments, the CD4 polypeptide comprises or has an amino acid sequence that is a consecutive fragment of SEQ ID NO: 79 which is at least 20, or at least 30, or at least 40, or at least 50, and up to 458 amino acids in length. Alternatively or additionally, in non-limiting various embodiments, the CD4 polypeptide comprises or has an amino acid sequence of amino acids 1 to 457, 1 to 50, 50 to 100, 100 to 150, 150 to 200, 200 to 250, 250 to 300, 300 to 350, 350 to 400, 397 to 418, or 400 to 457 of SEQ ID NO: 79. In certain embodiments, the transmembrane domain of the membrane-bound polypeptide comprises a CD4 polypeptide comprising or having amino acids 397 to 418 of SEQ ID NO: 79. SEQ ID NO: 79 is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 79] 
               
               
                   
                 MNRGVPFRHLLLVLQLALLPAATQGKKVVLGKKGDTVELT 
               
               
                   
               
               
                   
                 CTASQKKSIQFHWKNSNQIKILGNQGSFLTKGPSKLNDRA 
               
               
                   
               
               
                   
                 DSRRSLWDQGNFPLIIKNLKIEDSDTYICEVEDQKEEVQL 
               
               
                   
               
               
                   
                 LVEGLTANSDTHLLQGQSLTLTLESPPGSSPSVQCRSPRG 
               
               
                   
               
               
                   
                 KNIQGGKTLSVSQLELQDSGTWTCTVLQNQKKVEFKIDIV 
               
               
                   
               
               
                   
                 VLAFQKASSIVYKKEGEQVEFSFPLAFTVEKLTGSGELWW 
               
               
                   
               
               
                   
                 QAERASSSKSWITFDLKNKEVSVKRVTQDPKLQMGKKLPL 
               
               
                   
               
               
                   
                 HLTLPQALPQYAGSGNLTLALEAKTGKLHQEVNLVVMRAT 
               
               
                   
               
               
                   
                 QLQKNLTCEVWGPTSPKLMLSLKLENKEAKVSKREKAVWV 
               
               
                   
               
               
                   
                 LNPEAGMWQCLLSDSGQVLLESNIKVLPTWSTPVQPMALI 
               
               
                   
               
               
                   
                 VLGGVAGLLLFIGLGIFFCVRCRHRRRQAERMSQIKRLLS 
               
               
                   
               
               
                   
                 EKKTCQCPHRFQKTCSPI 
               
            
           
         
       
     
     2.1.3. Intracellular Domain 
     In certain non-limiting embodiments, the membrane-bound polypeptide further comprises an intracellular domain. In certain non-limiting embodiments, the intracellular domain provides an activation signal to a cell (e.g., a cell of the lymphoid lineage, e.g., a T cell). In certain embodiments, the intracellular domain of the membrane-bound polypeptides comprises an immune activating molecule. In certain embodiments, the immune activating molecule is a CD3ζ polypeptide. 
     In certain non-limiting embodiments, the intracellular domain of the membrane-bound polypeptide comprises a CD3ζ polypeptide or a fragment thereof. CD3ζ can activate or stimulate a cell. CD3ζ comprises 3 ITAMs, and transmits an activation signal to the cell (e.g., a cell of the lymphoid lineage, e.g., a T cell) after antigen is bound. The intracellular signaling domain of the CD3ζ-chain is the primary transmitter of signals from endogenous TCRs. In certain embodiments, the CD3ζ polypeptide comprises or has an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: NP_932170 (SEQ ID No: 15), or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. In certain non-limiting embodiments, the CD3ζ polypeptide comprises or has an amino acid sequence that is a consecutive fragment of SEQ ID NO: 15, which is at least 20, or at least 30, or at least 40, or at least 50, and up to 164 amino acids in length. Alternatively or additionally, in non-limiting various embodiments, the CD3ζ polypeptide comprises or has an amino acid sequence of amino acids 1 to 164, 1 to 50, 50 to 100, 52 to 164, 100 to 150, or 150 to 164 of SEQ ID NO: 15. In certain embodiments, the CD3ζ polypeptide comprises or has an amino acid sequence of amino acids 52 to 164 of SEQ ID NO: 15. SEQ ID NO: 15 is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 15] 
               
               
                   
                 MKWKALFTAAILQAQLPITEAQSFGLLDPKLCYLLDGILFI 
               
               
                   
               
               
                   
                 YGVILTALFLRVKFSRSADAPAYQQGQNQLYNELNLGRREE 
               
               
                   
               
               
                   
                 YDVLDKRRGRDPEMGGKPQRRKNPQEGLYNELQKDKMAEAY 
               
               
                   
               
               
                   
                 SEIGMKGERRRGKGHDGLYQGLSTATKDTYDALHMQALPPR 
               
            
           
         
       
     
     In certain embodiments, the CD3ζ polypeptide comprises or has an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: NP_001106864.2 (SEQ ID No: 13) or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. In certain non-limiting embodiments, the CD3ζ polypeptide comprises or has an amino acid sequence that is a consecutive fragment of SEQ ID NO: 13, which is at least about 20, or at least about 30, or at least about 40, or at least about 50, or at least about 90, or at least about 100, and up to 188 amino acids in length. Alternatively or additionally, in non-limiting various embodiments, the CD3ζ polypeptide comprises or has an amino acid sequence of amino acids 1 to 164, 1 to 50, 50 to 100, 100 to 150, or 150 to 188 of SEQ ID NO: 13. SEQ ID NO: 13 is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 13] 
               
               
                   
                 MKWKVSVLACILHVRFPGAEAQSFGLLDPKLCYLLDGILF 
               
               
                   
               
               
                   
                 IYGVIITALYLRAKFSRSAETAANLQDPNQLYNELNLGRR 
               
               
                   
               
               
                   
                 EEYDVLEKKRARDPEMGGKQRRRNPQEGVYNALQKDKMAE 
               
               
                   
               
               
                   
                 AYSEIGTKGERRRGKGHDGLYQDSHFQAVQFGNRREREGS 
               
               
                   
               
               
                   
                 ELTRILGLRARPKACRHKKPLSLPAAVS 
               
            
           
         
       
     
     In certain embodiments, the CD3ζ polypeptide comprises or has an amino acid sequence set forth in SEQ ID NO: 17 as provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 17] 
               
               
                   
                 RAKESRSAETAANLQDPNQLYNELNLGRREEYDVLEKKRA 
               
               
                   
               
               
                   
                 RDPEMGGKQQRRRNPQEGVYNALQKDKMAEAYSEIGTKGE 
               
               
                   
               
               
                   
                 RRRGKGHDGLYQGLSTATKDTYDALHMQTLAPR 
               
            
           
         
       
     
     In certain embodiments, the intracellular domain of the membrane-bound polypeptide comprises a murine CD3ζ polypeptide. 
     In certain embodiments, the intracellular domain of the membrane-bound polypeptide comprises a human CD3ζ polypeptide. 
     In certain non-limiting embodiments, the intracellular domain of the membrane-bound polypeptide provides an activation signal and a stimulation signal to a cell. In certain embodiments, the intracellular of the membrane-bound polypeptide domain comprises at least one costimulatory molecule or a fragment thereof. In certain embodiments, the at least one co-stimulatory signaling region comprises a CD28 polypeptide (e.g., the intracellular domain of CD28 or a fragment thereof), a 4-1BB polypeptide (e.g., the intracellular domain of 4-1BB or a fragment thereof), an OX40 polypeptide (e.g., the intracellular domain of OX40 or a fragment thereof), an ICOS polypeptide (e.g., the intracellular domain of ICOS or a fragment thereof), a DAP-10 polypeptide (e.g., the intracellular domain of DAP-10 or a fragment thereof), or a combination thereof. In certain embodiments, the at least one co-stimulatory signaling region comprises a CD28 polypeptide. In certain embodiments, the at least one co-stimulatory signaling region comprises an intracellular domain of CD28 or a fragment thereof. 
     In certain embodiments, the costimulatory molecule is a CD28 polypeptide (e.g., the intracellular domain of CD28 or a fragment thereof). The CD28 polypeptide can comprise or have an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least 100% homologous or identical to the sequence having a NCBI Reference No: P10747 or NP_006130 (SEQ ID NO: 14) or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. In certain embodiments, the CD28 polypeptide comprises or has an amino acid sequence that is a consecutive fragment of SEQ ID NO: 14 which is at least 20, or at least 30, or at least 40, or at least 50, and up to 220 amino acids in length. Alternatively or additionally, in non-limiting various embodiments, the CD28 polypeptide comprises or has an amino acid sequence of amino acids 1 to 220, 1 to 50, 50 to 100, 100 to 150, 150 to 200, or 200 to 220 of SEQ ID NO: 14. In certain embodiments, the CD28 polypeptide comprises or has an amino acid sequence of amino acids 181 to 220 of SEQ ID NO: 14. 
     In certain embodiments, the CD28 polypeptide comprises or has an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: NP_031668.3 (SEQ ID NO: 16) or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. In certain embodiments, the CD28 polypeptide comprises or has an amino acid sequence that is a consecutive fragment of SEQ ID NO: 16 which is at least about 20, or at least about 30, or at least about 40, or at least about 50, and up to 218 amino acids in length. Alternatively or additionally, in non-limiting various embodiments, the CD28 polypeptide comprises or has an amino acid sequence of amino acids 1 to 218, 1 to 50, 50 to 100, 100 to 150, 150 to 200, or 200 to 218 of SEQ ID NO: 16. In certain embodiments, the CD28 polypeptide comprises or has an amino acid sequence of amino acids 178 to 218 of SEQ ID NO: 16. SEQ ID NO: 16 is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 16] 
               
               
                   
                 MTLRLLFLALNFFSVQVTENKILVKQSPLLVVDSNEVSLS 
               
               
                   
               
               
                   
                 CRYSYNLLAKEFRASLYKGVNSDVEVCVGNGNFTYQPQFR 
               
               
                   
               
               
                   
                 SNAEFNCDGDFDNETVTFRLWNLHVNHTDIYFCKIEFMYP 
               
               
                   
               
               
                   
                 PPYLDNERSNGTIIHIKEKHLCHTQSSPKLFWALVVVAGV 
               
               
                   
               
               
                   
                 LFCYGLLVTVALCVIWTNSRRNRLLQSDYMNMTPRRPGLT 
               
               
                   
               
               
                   
                 RKPYQPYAPARDFAAYRP 
               
            
           
         
       
     
     In certain embodiments, the costimulatory molecule is a mouse CD28 polypeptide. In certain embodiments, the costimulatory molecule is a human CD28 polypeptide. 
     In certain embodiments, the intracellular domain of the membrane-bound polypeptide comprises two costimulatory molecules, e.g., CD28 and 4-1BB or CD28 and OX40. 
     In certain embodiments, the at least one co-stimulatory signaling region comprises a 4-1BB polypeptide. In certain embodiments, the at least one co-stimulatory signaling region comprises an intracellular domain of 4-1BB or a fragment thereof. 
     In certain embodiments, the costimulatory molecule is a 4-1BB polypeptide (e.g., the intracellular domain of 4-1BB or a fragment thereof). 4-1BB can act as a tumor necrosis factor (TNF) ligand and have stimulatory activity. The 4-1BB polypeptide can comprise or have an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: P41273 or NP_001552 (SEQ ID NO: 97) or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. SEQ ID NO: 97 is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 97] 
               
               
                   
                 MGNSCYNIVATLLLVLNFERTRSLQDPCSN 
               
               
                   
               
               
                   
                 CPAGTFCDNNRNQICSPCPPNSFSSAGGQR 
               
               
                   
               
               
                   
                 TCDICRQCKGVFRTRKECSSTSNAECDCTP 
               
               
                   
               
               
                   
                 GFHCLGAGCSMCEQDCKQGQELTKKGCKDC 
               
               
                   
               
               
                   
                 CFGTFNDQKRGICRPWTNCSLDGKSVLVNG 
               
               
                   
               
               
                   
                 TKERDVVCGPSPADLSPGASSVTPPAPARE 
               
               
                   
               
               
                   
                 PGHSPQIISFFLALTSTALLFLLFFLTLRF 
               
               
                   
               
               
                   
                 SVVKRGRKKLLYIFKQPFMRPVQTTQEEDG 
               
               
                   
               
               
                   
                 CSCRFPEEEEGGCEL 
               
            
           
         
       
     
     In accordance with the presently disclosed subject matter, a “4-1BB nucleic acid molecule” refers to a polynucleotide encoding a 4-1BB polypeptide. 
     In certain embodiments, the at least one co-stimulatory signaling region comprises an OX40 polypeptide. In certain embodiments, the at least one co-stimulatory signaling region comprises an intracellular domain of OX40 or a fragment thereof. 
     In certain embodiments, the costimulatory molecule is an OX40 polypeptide (e.g., the intracellular domain of OX40 or a fragment thereof). The OX40 polypeptide can comprise or have an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: P43489 or NP_003318 (SEQ ID NO: 18) or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. SEQ ID NO: 18 is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 18] 
               
               
                   
                 MCVGARRLGRGPCAALLLLGLGLSTVTGLHCVGDTYPSNDRCCHE 
               
               
                   
               
               
                   
                 CRPGNGMVSRCSRSQNTVCRPCGPGFYNDVVSSKPCKPCTWCNLR 
               
               
                   
               
               
                   
                 SGSERKQLCTATQDTVCRCRAGTQPLDSYKPGVDCAPCPPGHFSP 
               
               
                   
               
               
                   
                 GDNQACKPWTNCTLAGKHTLQPASNSSDAICEDRDPPATQPQETQ 
               
               
                   
               
               
                   
                 GPPARPITVQPTEAWPRTSQGPSTRPVEVPGGRAVAAILGLGLVL 
               
               
                   
               
               
                   
                 GLLGPLAILLALYLLRRDQRLPPDAHKPPGGGSFRTPIQEEQADA 
               
               
                   
               
               
                   
                 HSTLAKI 
               
            
           
         
       
     
     In accordance with the presently disclosed subject matter, an “OX40 nucleic acid molecule” refers to a polynucleotide encoding an OX40 polypeptide. 
     In certain embodiments, the at least one co-stimulatory signaling region comprises an ICOS polypeptide. In certain embodiments, the at least one co-stimulatory signaling region comprises an intracellular domain of ICOS or a fragment thereof. 
     In certain embodiments, the costimulatory molecule is an ICOS polypeptide (e.g., the intracellular domain of ICOS or a fragment thereof). The ICOS polypeptide can comprise or have an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to the sequence having a NCBI Reference No: NP_036224 (SEQ ID NO: 19) or a fragment thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. SEQ ID NO: 19 is provided below: 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 19] 
               
               
                   
                 MKSGLWYFFLFCLRIKVLIGEINGSANYEMFIFHNGGVQILCKYP 
               
               
                   
               
               
                   
                 DIVQQFKMQLLKGGQILCDLIKTKGSGNIVSIKSLKFCHSQLSNNS 
               
               
                   
               
               
                   
                 VSFFLYNLDHSHANYYFCNLSIFDPPPFKVTLIGGYLHIYESQLCC 
               
               
                   
               
               
                   
                 QLKFWLPIGCAAFVVVCILGCILICWLIKKKYSSSVHDPNGEYMFM 
               
               
                   
               
               
                   
                 RAVNTAKKSRLTDVIL 
               
            
           
         
       
     
     In accordance with the presently disclosed subject matter, an “ICOS nucleic acid molecule” refers to a polynucleotide encoding an ICOS polypeptide. 
     In certain embodiments, the at least one co-stimulatory signaling region comprises two costimulatory molecules or fragments thereof. In certain embodiments, the at least one co-stimulatory signaling region comprises a CD28 polypeptide (e.g., an intracellular domain of CD28 or a fragment thereof) and a 4-1BB polypeptide (e.g., an intracellular domain of 4-1BB or a fragment thereof). 
     In certain non-limiting embodiments, the intracellular domain of the membrane-bound polypeptide alone does not provide an activation signal to a cell. In certain embodiments, the intracellular domain of the membrane-bound polypeptide does not comprise a costimulatory molecule. 
     In certain embodiments, the intracellular domain of the membrane-bound polypeptide does not comprise a CD3zeta polypeptide. 
     In certain embodiments, the intracellular domain of the membrane-bound polypeptide further comprises a suicide gene. Suitable suicide genes include, but are not limited to, Herpes simplex virus thymidine kinase (hsv-tk), and inducible Caspase 9 Suicide gene (iCasp-9). In certain embodiments, the intracellular domain of the membrane-bound polypeptide further comprises a truncated human epidermal growth factor receptor (EGFRt) polypeptide. A truncated EGFRt polypeptide can enable T cell elimination by administering anti-EGFR monoclonal antibody (e.g., cetuximab). 
     In certain embodiments, the membrane-bound polypeptide comprises a synNotch module. SynNotch modules are disclosed in U.S. Pat. No. 9,670,281 and Morsut et al,  Cell,  164, 780-791, 2016, each of which is incorporated by reference in its entirety. 
     2.2. Soluble Polypeptide 
     In certain embodiments, the soluble polypeptide comprises a dimerization domain that is capable of dimerizing with a dimerization domain comprised in a membrane-bound polypeptide disclosed herein. In certain embodiments, the membrane-bound polypeptide is a membrane-bound polypeptide disclosed herein, e.g., in Section 2.1. In certain embodiments, the dimerization domain comprises a leucin zipper domain. The dimerization domain can be any of the dimerization domains disclosed in Section 2.1.1. 
     In certain embodiments, the soluble polypeptide comprises a dimerization domain and an antigen-binding domain that is capable of binding to an antigen. 
     In certain embodiments, the soluble polypeptide comprises a dimerization domain and a cytokine or a chemokine. In certain embodiments, the soluble polypeptide further comprises a tag. 
     In certain embodiments, the leucine zipper domain of the membrane-bound polypeptide and the leucine zipper domain of the soluble polypeptide are a pair of orthogonal zippers, i.e., they are the specific partners for each other to form heterodimers. 
     2.2.1. Cytokine/Chemokine 
     In certain embodiments, the cytokine/chemokine is capable of enhancing the immune response of an immunoresponsive cell and/or cause cell death of a malignant or infected cell. In certain embodiments, the cytokine/chemokine is an anti-tumor cytokine/chemokine. In certain embodiments, the cytokine or the chemokine comprises or has an amino acid sequence that is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous or identical to a cytokine/chemokine, or fragments thereof, and/or may optionally comprise up to one or up to two or up to three conservative amino acid substitutions. Non-limiting example of cytokine include IL-1, IL-2, IL-3, IL-7, IL-10, IL-12, IL-15, IL-17, IL-18, IL-21, IL-22, granulocyte macrophage colony-stimulating factor (GM-CSF), IFN-γ, CXCL1, IL-23, and CXCL10. Non-limiting examples of chemokine include CCL1, CCL17, CCL8, CCL16, CCL18, and CCL22. 
     CCL1/CCL8/CCL16/CCL18 ligands can interact or pair with CCR8. CCL17/CCL22 ligands can interact or pair with CCR4. These receptors are targets for regulatory T cells, and subsets of T and B cell lymphomas making them possible therapeutic targets. 
     In certain embodiments, the chemokine is CCL1. In certain embodiments, the CCL1 is mouse CCL1. In certain embodiments, the mouse CCL1 comprises the amino acid sequence set forth in SEQ ID NO: 80. In certain embodiments, the CCL1 is human CCL1. In certain embodiments, the human CCL1 comprises the amino acid sequence set forth in SEQ ID NO: 81. SEQ ID Nos: 80 and 81 are provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 80] 
               
               
                   
                 KSMLTVSNSCCLNTLKKELPLKFIQCYRKMGSSC 
               
               
                   
               
               
                   
                 PDPPAWFRLNKGRESCASTNKTWVQNHLKKVNPC 
               
               
                   
               
               
                   
                 [SEQ ID NO: 81] 
               
               
                   
                 KSMQVPFSRCCFSFAEQEIPLRAILCYRNTSSIC 
               
               
                   
               
               
                   
                 SNEGLIFKLKRGKEACALDTVGWVQRHRKMLRHC 
               
               
                   
               
               
                   
                 PSKRK 
               
            
           
         
       
     
     In certain embodiments, the chemokine is CCL17. In certain embodiments, the CCL17 is mouse CCL17. In certain embodiments, the mouse CCL17 comprises the amino acid sequence set forth in SEQ ID NO: 82. In certain embodiments, the CCL17 is human CCL17. In certain embodiments, the human CCL17 comprises the amino acid sequence set forth in SEQ ID NO: 83. SEQ ID Nos: 82 and 83 are provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 82] 
               
               
                   
                 ARATNVGRECCLDYFKGAIPIRKLVSWYKTSVECS 
               
               
                   
               
               
                   
                 RDAIVFLTVQGKLICADPKDKHVKKAIRLVKNPRP 
               
               
                   
               
               
                   
                 [SEQ ID NO: 83] 
               
               
                   
                 ARGTNVGRECCLEYFKGAIPLRKLKTWYQTSEDCS 
               
               
                   
               
               
                   
                 RDAIVFVTVQGRAICSDPNNKRVKNAVKYLQSLER 
               
               
                   
               
               
                   
                 S 
               
            
           
         
       
     
     In certain embodiments, the chemokine is CCL18. In certain embodiments, the CCL18 is human CCL18. In certain embodiments, the human CCL18 comprises the amino acid sequence set forth in SEQ ID NO: 84. SEQ ID No: 84 is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 84] 
               
               
                   
                 AQVGINKELCCLVYTSWQIPQKFIVDYSETSPQCP 
               
               
                   
               
               
                   
                 KPGVILLTKRGRQICADPNKKWVQKYISDLKLNA 
               
            
           
         
       
     
     In certain embodiments, the chemokine is CCL22. In certain embodiments, the CCL22 is mouse CCL22. In certain embodiments, the mouse CCL22 chemokine comprises the amino acid sequence set forth in SEQ ID NO: 85. In certain embodiments, the CCL22 is human CCL22. In certain embodiments, the human CCL22 comprises the amino acid sequence set forth in SEQ ID NO: 86. SEQ ID Nos: 85 and 86 are provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 85] 
               
               
                   
                 GPYGANVEDSICCQDYIRHPLPSRLVKEFFWTSKS 
               
               
                   
               
               
                   
                 CRKPGVVLITVKNRDICADPRQVWVKKLLHKLS 
               
               
                   
               
               
                   
                 [SEQ ID NO: 86] 
               
               
                   
                 GPYGANMEDSVCCRDYVRYRLPLRVVKHEYWTSDS 
               
               
                   
               
               
                   
                 CPRPGVVLLTERDKEICADPRVPWVKMILNKLSQ 
               
            
           
         
       
     
     2.2.2. Antigen Binding Domain 
     In certain embodiments, the antigen binding domain of the soluble polypeptide comprises a single-chain variable fragment (scFv), a soluble ligand, a cytokine, or a non-scFv-based antigen recognition motif, or a combination thereof. 
     In certain non-limiting embodiments, the antigen binding domain of the soluble polypeptide (embodied, for example, an scFv or an analog thereof) binds to an antigen with a dissociation constant (K d ) of about 2×10 −7 M or less. In certain embodiments, the K d  is about 2×10 −7  M or less, about 1×10 −7  M or less, about 9×10 −8  M or less, about 1×10 −8  M or less, about 9×10 −9  M or less, about 5×10 −9  M or less, about 4×10 −9  M or less, about 3×10 −9  or less, about 2×10 −9  M or less, or about 1×10 −9 M or less. In certain non-limiting embodiments, the K d  is about 3×10 −9 M or less. In certain non-limiting embodiments, the K d  is from about 1×10 −9  M to about 3×10 −7  M. In certain non-limiting embodiments, the K d  is from about 1.5×10 −9  M to about 3×10 −7  M. 
     Binding of the antigen binding domain (for example, in an scFv or an analog thereof) can be confirmed by, for example, enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), FACS analysis, bioassay (e.g., growth inhibition), or Western Blot assay. Each of these assays generally detect the presence of protein-antibody complexes of particular interest by employing a labeled reagent (e.g., an antibody, or an scFv) specific for the complex of interest. For example, the scFv can be radioactively labeled and used in a radioimmunoassay (MA) (see, for example, Weintraub, B., Principles of Radioimmunoassays, Seventh Training Course on Radioligand Assay Techniques, The Endocrine Society, March 1986, which is incorporated by reference herein). The radioactive isotope can be detected by such means as the use of a γ counter or a scintillation counter or by autoradiography. In certain embodiments, the antigen binding domain is labeled with a fluorescent marker. Non-limiting examples of fluorescent markers include green fluorescent protein (GFP), blue fluorescent protein (e.g., EBFP, EBFP2, Azurite, and mKalama1), cyan fluorescent protein (e.g., ECFP, Cerulean, and CyPet), and yellow fluorescent protein (e.g., YFP, Citrine, Venus, and YPet). 
     In certain embodiments, the antigen binding domain of the soluble polypeptide specifically binds to an antigen. In certain embodiments, the antigen binding domain is an scFv. In certain embodiments, the scFv is a human scFv. In certain embodiments, the scFv is a humanized scFv. In certain embodiments, the scFv is a murine scFv. In certain embodiments, the extracellular antigen-binding domain is a Fab, which is optionally crosslinked. In certain embodiments, the extracellular antigen-binding domain is a F(ab) 2 . In certain embodiments, any of the foregoing molecules may be comprised in a fusion protein with a heterologous sequence to form the extracellular antigen-binding domain. In certain embodiments, the scFv is identified by screening scFv phage library with an antigen-Fc fusion protein. In certain embodiments, the antigen is a tumor antigen. In certain embodiments, the antigen is a pathogen antigen. 
     2.2.3. Antigens 
     In certain embodiments, the antigen binding domain of the soluble polypeptide binds to a tumor antigen. Any tumor antigen can be used in the tumor-related embodiments described herein. The antigen can be expressed as a peptide or as an intact protein or fragment thereof. The intact protein or a fragment thereof can be native or mutagenized. Non-limiting examples of tumor antigens include CD2, CD3, CD4, CD5, CD7, CD8, CD19, CD20, CD22, VpreB, CD30, CD33, CD38, CD40, CD44v6, CD70, CD79a, CD70b, CLL-1/CLEC12A, CD123, IL-3R complex, TIM-3, BCMA, TACI, SLAMF7, CD244, E-cadherin, B7-H3, B7-H4, carbonic anhydrase IX (CA1X), carcinoembryonic antigen (CEA), CD10, CD34, CD38, CD41, CD44, CD49f, CD56, CD74, CD133, CD138, an antigen of a cytomegalovirus (CMV) infected cell (e.g., a cell surface antigen), epithelial glycoprotein-2 (EGP-2), epithelial glycoprotein-40 (EGP-40), epithelial cell adhesion molecule (EpCAM), receptor tyrosine-protein kinases erb-B2,3,4 (erb-B2,3,4), folate-binding protein (FBP), fetal acetylcholine receptor (AChR), folate receptor-α, Ganglioside G2 (GD2), Ganglioside G3 (GD3), human Epidermal Growth Factor Receptor 2 (HER-2), human telomerase reverse transcriptase (hTERT), Interleukin-13 receptor subunit alpha-2 (IL-13Rα2), κ-light chain, kinase insert domain receptor (KDR), Lewis Y (LeY), L1 cell adhesion molecule (L1CAM), melanoma antigen family A, 1 (MAGE-A1), Mucin 16 (MUC16), Mucin 1 (MUC1), Mesothelin (MSLN), ERBB2, MAGEA3, p53, MART1, GP100, Proteinase3 (PR1), Tyrosinase, Survivin, hTERT, EphA2, NKG2D ligands, cancer-testis antigen NY-ESO-1, oncofetal antigen (h5T4), prostate stem cell antigen (PSCA), prostate-specific membrane antigen (PSMA), ROR1, tumor-associated glycoprotein 72 (TAG-72), vascular endothelial growth factor R2 (VEGF-R2), and Wilms tumor protein (WT-1), BCMA, NKCS1, EGF1R, EGFR-VIII, CD99, ADGRE2, CCR1, LILRB2, PRAME and ERBB. 
     In certain embodiments, the antigen binding domain of the soluble polypeptide binds to a human CD19 polypeptide. In certain embodiments, the antigen binding domain of the soluble polypeptide binds to the extracellular domain of a human CD19 protein. 
     In certain embodiments, the antigen binding domain of the soluble polypeptide binds to an immune checkpoint molecule. Non-limiting example of immune checkpoint molecules include PD-L1, CD200, B7-H3, B7-H4, HVEM, Galectin9, PD-1, CTLA-4, CD200R, TIM-3, Lag-3 and TIGIT. 
     In certain embodiments, the antigen binding domain of the soluble polypeptide binds to an activating receptor, wherein the binding of the antigen binding domain to the activating receptor is capable of activating an antigen presenting cell (APC). Non-limiting example of immune checkpoint molecules include CD40, Toll Like Receptors (TLRs), FLT3, RANK, and GM-CSF receptor. 
     In certain embodiments, the antigen binding domain of the soluble polypeptide binds to a biomarker of a hematopoietic lineage cell. Non-limiting example of immune checkpoint molecules include CD3, CD16, CD33, c-Kit, CD161, CD19, CD20, VpPreB, luteinizing hormone receptor (LHCGR), CD123, IL-3R complex, CLEC12A/CLL-1. 
     In certain embodiments, the antigen binding domain of the soluble polypeptide binds to a pathogen antigen, e.g., for use in treating and/or preventing a pathogen infection or other infectious disease, for example, in an immunocompromised subject. Non-limiting examples of pathogens include a virus, bacteria, fungi, parasite and protozoa capable of causing disease. 
     Non-limiting examples of viruses include, Retroviridae (e.g. human immunodeficiency viruses, such as HIV-1 (also referred to as HDTV-III, LAVE or HTLV-III/LAV, or HIV-III; and other isolates, such as HIV-LP; Picornaviridae (e.g. polio viruses, hepatitis A virus; enteroviruses, human Coxsackie viruses, rhinoviruses, echoviruses); Calciviridae (e.g. strains that cause gastroenteritis); Togaviridae (e.g. equine encephalitis viruses, rubella viruses); Flaviridae (e.g. dengue viruses, encephalitis viruses, yellow fever viruses); Coronoviridae (e.g. coronaviruses); Rhabdoviridae (e.g. vesicular stomatitis viruses, rabies viruses); Filoviridae (e.g. ebola viruses); Paramyxoviridae (e.g. parainfluenza viruses, mumps virus, measles virus, respiratory syncytial virus); Orthomyxoviridae (e.g. influenza viruses); Bungaviridae (e.g. Hantaan viruses, bunga viruses, phleboviruses and Naira viruses); Arena viridae (hemorrhagic fever viruses); Reoviridae (e.g. reoviruses, orbiviurses and rotaviruses); Birnaviridae; Hepadnaviridae (Hepatitis B virus); Parvovirida (parvoviruses); Papovaviridae (papilloma viruses, polyoma viruses); Adenoviridae (most adenoviruses); Herpesviridae (herpes simplex virus (HSV) 1 and 2, varicella zoster virus, cytomegalovirus (CMV), herpes virus; Poxviridae (variola viruses, vaccinia viruses, pox viruses); and Iridoviridae (e.g. African swine fever virus); and unclassified viruses (e.g. the agent of delta hepatitis (thought to be a defective satellite of hepatitis B virus), the agents of non-A, non-B hepatitis (class 1=internally transmitted; class 2=parenterally transmitted (i.e. Hepatitis C); Norwalk and related viruses, and astroviruses). 
     Non-limiting examples of bacteria and/or fungi include  Pasteurella, Staphylococci, Streptococcus, Escherichia coli, Pseudomonas species , and  Salmonella  species. Specific examples of infectious bacteria include but are not limited to,  Helicobacter pyloris, Borelia burgdorferi, Legionella pneumophilia, Mycobacteria  sps (e.g.  M. tuberculosis, M. avium, M. intracellulare, M. kansaii, M. gordonae ),  Staphylococcus aureus, Neisseria gonorrhoeae, Neisseria meningitidis, Listeria monocytogenes, Streptococcus pyogenes  (Group A  Streptococcus ),  Streptococcus agalactiae  (Group B  Streptococcus ),  Streptococcus  ( viridans  group),  Streptococcus faecalis, Streptococcus bovis, Streptococcus  (anaerobic sps.),  Streptococcus pneumoniae , pathogenic  Campylobacter  sp.,  Enterococcus  sp.,  Haemophilus influenzae, Bacillus anthracis, Corynebacterium diphtheriae, corynebacterium  sp.,  Erysipelothrix rhusiopathiae, Clostridium perfringerns, Clostridium tetani, Enterobacter aerogenes, Klebsiella pneumoniae, Pasteurella multocida, Bacteroides  sp.,  Fusobacterium nucleatum, Streptobacillus moniliformis, Treponema pallidium, Treponema pertenue, Leptospira, Rickettsia, Aspergillus  species and  Actinomyces israelli.    
     2.2.4. Tags 
     In certain embodiments, the soluble polypeptide further comprises a tag. In certain embodiments, the tag comprises an epitope tag, which comprises an epitope recognized by an antibody. In certain embodiments, the epitope tag is selected from the group consisting of a Myc-tag, a HA-tag, a Flag-tag, a V5-tag, a T7 tag, and combinations thereof. In certain embodiments, the tag comprises an affinity tag that binds to a substrate. In certain embodiments, the affinity tag is selected from the group consisting of a His-tag, a Strep-tag, an E-tag, a streptavidin binding protein tag (SBP-tag), and combinations thereof. 
     Furthermore, the soluble polypeptide can further comprise a mimotope recognized by a second antibody. Binding of the second antibody to the mimotope can mediates depletion of a cell comprising the membrane-bound polypeptide. In certain embodiments, the mimotope is a CD20 mimotope recognized by an anti-CD20 antibody. In certain embodiments, the anti-CD20 antibody is Rituxumab. In certain embodiments, the CD20 mimotope is a circular CD20 mimotope. 
     In certain embodiments, the CD20 mimotope comprises or has the amino acid sequence set forth in SEQ ID NO: 77, which is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 77] 
               
               
                   
                 CPYSNPSLC 
               
            
           
         
       
     
     3. Systems 
     The presently disclosed subject matter provides systems for immunotherapy. In certain embodiments, the system comprises a membrane-bound polypeptide disclosed herein and a soluble polypeptide disclosed herein. 
     3.1. Functional Sorting Zip Construct with a Blocking Spacer 
     The presently disclosed subject matter provides a system, comprising: a) a membrane-bound polypeptide disclosed herein (e.g., a membrane-bound polypeptide comprising: i) a transmembrane domain, ii) an intracellular domain, and iii) an extracellular domain that comprises a first dimerization domain and a blocking spacer), and b) a soluble polypeptide disclosed herein (e.g., a soluble polypeptide comprising i) a second dimerization domain that is capable of dimerizing with the first dimerization domain, and ii) an antigen binding domain that binds to an antigen). In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain, and the blocking spacer prevents dimerization of the membrane-bound polypeptide with the soluble polypeptide when the membrane-bound polypeptide and the soluble polypeptide are not expressed from the same cell. 
     In certain embodiments, the blocking spacer has a length of no more than about 25 amino acids. In certain embodiments, the blocking spacer has a length of between about 5 amino acids and about 25 amino acids. In certain embodiments, the blocking spacer is a truncated CD28 spacer or an IgG1 hinge. 
     3.2. Functional Sorting Zip Construct with a Self-Blocking Feature 
     The presently disclosed subject matter provides a system, comprising: a) a membrane-bound polypeptide disclosed herein (e.g., a membrane-bound polypeptide comprising: i) a transmembrane domain, ii) an intracellular domain, and iii) an extracellular domain that comprises a first dimerization domain and a second dimerization domain that is capable of dimerizing with the first dimerization domain), and b) a soluble polypeptide disclosed herein (e.g., a soluble polypeptide comprising i) a third dimerization domain that is capable of dimerizing with the first dimerization domain, and ii) an antigen binding domain that binds to an antigen). In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain. 
     In certain embodiments, the antigen is selected from the group consisting of tumor antigens, pathogen antigens, immune checkpoint molecules, activating receptors, and biomarkers of a hematopoietic lineage cell. 
     3.2.1. Functional Sorting Zip Construct Targeting Tumor Antigens 
     The presently disclosed subject matter provides systems for targeting tumor antigens comprising any membrane-bound polypeptide and/or any soluble polypeptide discloses herein, or any system disclosed herein. In certain embodiments, the antigen of the antigen binding domain of the soluble polypeptide disclosed herein, optionally comprised in any system discloses herein, is a tumor antigen. In certain embodiments, the tumor antigen is selected from the group consisting of CD2, CD3, CD4, CDS, CD7, CD8, CD19, CD20, CD22, VpreB, CD79a, CD79b, CD30, CD33, CD38, CD40, CD44v6, CD70, CLL-1/CLEC12A, CD123, IL-3R complex, TIM-3, BCMA, TACI, SLAMF7, CD244, Epcam, E-cadherin, B7-H3, B7-H4, and fragments or combinations thereof. 
     3.2.2. Functional Sorting Zip Construct for Activating APCs 
     The presently disclosed subject matter provides systems for activating APCs comprising any membrane-bound polypeptide and/or any soluble polypeptide discloses herein, or any system disclosed herein. In certain embodiments, the antigen of the antigen binding domain of the soluble polypeptide, optionally comprised in any system discloses herein, is an activating receptor. In certain embodiments, the binding of the antigen binding domain to the activating receptor is capable of activating an antigen presenting cell (APC). In certain embodiments, the APC is a professional APC. In certain embodiments, the professional APC is selected from the group consisting of dendritic cells, macrophages, B cells, and combinations thereof. In certain embodiments, the APC is a non-professional APC. In certain embodiments, the APC is a cell of the myeloid lineage. In certain embodiments, the cell of myeloid lineage is selected from the group consisting of dendritic cells, macrophages, monocytes and combinations thereof. In certain embodiments, the activating receptor is selected from the group consisting of CD40, Toll Like Receptors (TLRs), FLT3, RANK, GM-CSF receptor, and fragments or combinations thereof 
     3.2.3. Functional Sorting Zip Construct Targeting Immune Checkpoint Blockers 
     The presently disclosed subject matter provides systems for targeting immune checkpoint blockers comprising any membrane-bound polypeptide and/or any soluble polypeptide discloses herein, or any system disclosed herein. In certain embodiments, the antigen of the antigen binding domain of the soluble polypeptide disclosed herein, optionally comprised in any system discloses herein, is an immune checkpoint molecule. In certain embodiments, binding of the antigen binding domain to the immune checkpoint molecule is capable of blocking an immune checkpoint signal in an immunoresponsive cell. In certain embodiments, the immune checkpoint molecule is selected from the group consisting of PD-L1, CD200, B7-H3, B7-H4, HVEM, Galectin9, PD-1, CTLA-4, CD200R, TIM-3, Lag-3, TIGIT, and fragments or combinations thereof. 
     3.2.4. Functional Sorting Zip Construct for Conditioning Regimen for Hematopoietic Stem Cell Transplantation 
     The presently disclosed subject matter provides systems for conditioning regimen for hematopoietic stem cell transplantation, comprising any membrane-bound polypeptide and/or any soluble polypeptide discloses herein, or any system disclosed herein. In certain embodiments, the antigen of the antigen binding domain of the soluble polypeptide disclosed herein, optionally comprised in any system discloses herein, is a biomarker of a hematopoietic lineage cell. In certain embodiments, the biomarker of a hematopoietic lineage cell is selected from the group consisting of CD3, CD16, CD33, c-Kit, CD161, CD19, CD20, vPreB/CD179a (preB cell receptor), luteinizing hormone receptor (LHCGR), CD123, IL-3R complex, CLEC12A/CLL-1, and combinations thereof. In certain embodiments, the system comprises at least four soluble polypeptides, wherein the antigen binding domain of each soluble polypeptide binds to a different biomarker of a hematopoietic lineage cell. In certain embodiments, each of the at least four soluble polypeptides comprises a dimerization domain that comprises a leucine zipper domain. In certain embodiments, the system comprises a first soluble polypeptide that binds to CD3, a second soluble polypeptide that binds to CD19, a third soluble polypeptide that binds to CD161 and a fourth soluble polypeptide that binds to c-Kit. 
     In certain embodiments, the dimerization domain that interacts with the membrane-bound polypeptide (also referred to as “capture leucine zipper” or “transmembrane capture leucine zipper”) is the appended heterodimerizing leucine zipper of the soluble polypeptide (also referred to as “secreted leucine zippers” or “secreted molecules”), which also comprise an affinity tag and an antigen-binding domain (e.g., a scFv or ligand) that binds to a target antigen. See e.g.,  FIG. 1 , the system on the left. The membrane-bound polypeptide and soluble polypeptides may have the same heterodimerizing leucine zipper domain (e.g., RR12EE345L) if interacting with the same heterodimerizing leucine zipper domain (e.g., EE12RR345L). In certain embodiments, the leucine zipper of the multiple soluble polypeptides (e.g., four soluble polypeptides) and the leucine zipper of the membrane-bound polypeptide are non-orthogonal zippers, i.e., degenerate zippers, which allow all the antigens to be targeted by a membrane-bound polypeptide (a CD3ζ comprising ZipR-CAR), which can result in killing of that component of the hematopoietic system by the effector cells. 
     3.2.5. Functional Sorting Zip Construct with AND-CAR 
     The presently disclosed subject matter provides systems for conditioning regimen for hematopoietic stem cell transplantation, comprising any membrane-bound polypeptide and/or any soluble polypeptide discloses herein, or any system disclosed herein. In certain embodiments, the system further comprises c) a chimeric antigen receptor (CAR) comprising a second antigen binding domain (e.g., one t binds to a second antigen), a transmembrane domain, and an intracellular activating domain. The CAR can activate an immunoresponsive cell, e.g., a T cell. In certain embodiments, the system further comprises an inhibitory receptor comprising a leucine zipper domain, wherein the inhibitory receptor binds to a third antigen, e.g., the inhibitory receptor comprising a third antigen binding domain that binds to a third antigen. The inhibitory receptor can be membrane-bound. The inhibitory receptor can be a tyrosine phosphatase-based inhibitory receptor. In certain embodiments, the tyrosine phosphatase is selected from the group consisting of PTPRJ, PTPRC, PTPN22, and PTPN6. In the absence of the third antigen, the inhibitory receptor constitutively inhibits and/or deactivates the CAR, e.g., by dephosphorylation. Binding of the inhibitory receptor to the third antigen prevents the inhibition and/or deactivation of the CAR by the inhibitory receptor, e.g., upon binding of the inhibitory receptor, the inhibitory receptor does not inhibit the CAR. In summary, the inhibitory receptor is constitutively inhibitory, but can be “turned off” in the presence of the third antigen (e.g., the CAR inhibitory capacity of the inhibitory receptor is turned off). 
     3.3. Zip Construct with Membrane Bound Cytokines and/or Chemokines 
     The presently disclosed subject matter provides a system, comprising: a) a membrane-bound polypeptide disclosed herein (e.g., a membrane-bound polypeptide comprising a transmembrane domain, an intracellular domain and an extracellular domain that comprises a first dimerization domain), and b) a soluble polypeptide (e.g., a soluble polypeptide comprising a second dimerization domain that is capable of dimerizing with the first dimerization domain, and a cytokine or a chemokine). In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain. 
     In certain embodiments, the cytokine is selected from the group consisting of IL-1, IL-2, IL-3, IL-7, IL-10, IL-12, IL-15, IL-17, IL-18, IL-21, IL-22, and combinations thereof. 
     In certain embodiments, the chemokine is selected from the group consisting of CCL1, CCL17, CCL8, CCL16, CCL18, CCL22, and combinations thereof. 
     In certain embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a third dimerization domain, and wherein the second dimerization domain is capable of dimerizing with the first dimerization domain prior to dimerization between the first dimerization domain and the third dimerization domain. 
     3.4. Common Features of Systems Disclosed Herein 
     Any features of the membrane-bound polypeptides or soluble polypeptides disclosed herein can be applied to the systems disclosed herein, e.g., the systems disclosed in Sections 3.1, 3.2, and 3.3. The following exemplary features are applicable to any systems disclosed herein, e.g., the systems disclosed in Sections 3.1, 3.2, and 3.3. 
     In certain embodiments, the extracellular domain of the membrane-bound polypeptide further comprises a linker between the first dimerization domain and the second dimerization domain. In certain embodiments, the linker comprises the amino acid sequence set forth in SEQ ID NO: 3. 
     In certain embodiments, the first dimerization domain comprises the amino acid sequence set forth in SEQ ID NO: 1, SEQ ID NO: 2, or SEQ ID NO: 67, and each of the second and third dimerization domains comprises the amino acid sequence set forth in SEQ ID NO: 2, SEQ ID NO: 1, or SEQ ID NO: 67. In certain embodiments, the soluble polypeptide and the membrane-bound polypeptide are capable of forming a dimer when expressed from the same cell. In certain embodiments, the soluble polypeptide and the membrane-bound polypeptide are not capable of forming a dimer when expressed from different cells due to the dimerization between the first dimerization domain and the second dimerization domain of the membrane-bound polypeptide. 
     In certain embodiments, the intracellular domain of the membrane-bound polypeptide comprises a CD3-ζ domain, a costimulatory domain, or a combination thereof. 
     In certain embodiments, the system further comprises a suicide module. In certain embodiments, the suicide module is an inducible Caspase 9 polypeptide (iCasp9). 
     In certain embodiments, the extracellular domain further comprises a spacer/hinge domain between the first dimerization domain and the transmembrane domain. In certain embodiments, the spacer/hinge domain comprises an epitope of a first antibody, wherein binding of the antibody to the epitope mediates depletion of a cell comprising the membrane-bound polypeptide. In certain embodiments, the spacer/hinge domain comprises a Thy1.1 molecule, circular CD20 mimotope, or a truncated EGFR molecule (EGFRt) 
     In certain embodiments, the antigen binding domain of the soluble polypeptide comprises a single-chain variable fragment (scFv), a soluble ligand, a cytokine, a non-scFv-based antigen recognition motif, or a combination thereof. 
     In certain embodiments, the membrane-bound polypeptide is expressed from a first vector. In certain embodiments, the soluble polypeptide is expressed from a second vector. In certain embodiments, the first vector and/or second vector is a viral vector or a transposon-based vector. In certain embodiments, the first vector is the same as the second vector. 
     In certain embodiments, the leucine zipper domains are orthogonal zippers. 
     In certain embodiments, the membrane-bound polypeptide and/or the soluble polypeptide further comprises a tag. In certain embodiments, the tag comprises an epitope tag that is recognized by a first antibody. In certain embodiments, the epitope tag is selected from the group consisting of a Myc-tag, a HA-tag, a Flag-tag, a V5-tag, a T7-tag, and combinations thereof. In certain embodiments, the tag comprises an affinity tag that binds to a substrate. In certain embodiments, the affinity tag is selected from the group consisting of a His-tag, a Strep-tag, an E-tag, a streptavidin binding protein tag (SBP-tag), and combinations thereof. 
     In certain embodiments, the membrane-bound polypeptide and/or the soluble polypeptide further comprises a mimotope recognized by an antibody, wherein binding of the antibody to the mimotope mediates depletion of a cell comprising the membrane-bound polypeptide. In certain embodiments, the mimotope is CD20. 
     3.5. Exemplary Systems 
     In certain embodiments, the membrane-bound polypeptide comprises an EE12RR345L leucine zipper, a myc tag, a CD28 costimulatory domain, a CD3ζ polypeptide, an E2A peptide, and a Thy1.1 polypeptide. (No spacer; only a short linker: AAASGSL [SEQ ID NO: 94]; no myc staining). In certain embodiments, the membrane-bound polypeptide comprises SEQ ID NO: 24. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 24] 
               
               
                   
                 METDTLLLWVLLLWVPGSTGLEIEAAFLERENTALETRVA 
               
               
                   
               
               
                   
                 ELRQRVQRLRNRVSQYRTRYGPLGGGKGSGEQKLISEEDL 
               
               
                   
               
               
                   
                 AAASGSLIYIWAPLAGICVALLLSLIITLICYNSRRNRLL 
               
               
                   
               
               
                   
                 QSDYMNMTPRRPGLTRKPYQPYAPARDFAAYRPRAKFSRS 
               
               
                   
               
               
                   
                 AETAANLQDPNQLYNELNLGRREEYDVLEKKRARDPEMGG 
               
               
                   
               
               
                   
                 KQQRRRNPQEGVYNALQKDKMAEAYSEIGTKGERRRGKGH 
               
               
                   
               
               
                   
                 DGLYQGLSTATKDTYDALHMQTLAPRGTGQCTNYALLKLA 
               
               
                   
               
               
                   
                 GDVESNPGPGSMNPAISVALLLSVLQVSRGQKVTSLTACL 
               
               
                   
               
               
                   
                 VNQNLRLDCRHENNTKDNSIQHEFSLTREKRKHVLSGTLG 
               
               
                   
               
               
                   
                 IPEHTYRSRVTLSNQPYIKVLTLANFTTKDEGDYFCELRV 
               
               
                   
               
               
                   
                 SGANPMSSNKSISVYRDKLVKCGGISLLVQNTSWMLLLLL 
               
               
                   
               
               
                   
                 SLSLLQALDFISL 
               
            
           
         
       
     
     In certain embodiments, the membrane-bound polypeptide comprises an EE12RR345L leucine zipper, a myc tag, a CD28EC-9C hinge, a CD28 costimulatory domain, a CD3ζ polypeptide, an E2A peptide, and a Thy1.1 polypeptide. (CD28-hinge nine amino acid spacer; no myc staining). In certain embodiments, the membrane-bound polypeptide comprises SEQ ID NO: 25. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 25] 
               
               
                   
                 METDTLLLWVLLLWVPGSTGLEIEAAFLERENTALETRVA 
               
               
                   
               
               
                   
                 ELRQRVQRLRNRVSQYRTRYGPLGGGKGSGEQKLISEEDL 
               
               
                   
               
               
                   
                 AAACHTQSSPKLGSLIYIWAPLAGICVALLLSLIITLICY 
               
               
                   
               
               
                   
                 NSRRNRLLQSDYMNMTPRRPGLTRKPYQPYAPARDFAAYR 
               
               
                   
               
               
                   
                 PRAKFSRSAETAANLQDPNQLYNELNLGRREEYDVLEKKR 
               
               
                   
               
               
                   
                 ARDPEMGGKQQRRRNPQEGVYNALQKDKMAEAYSEIGTKG 
               
               
                   
               
               
                   
                 ERRRGKGHDGLYQGLSTATKDTYDALHMQTLAPRGTGQCT 
               
               
                   
               
               
                   
                 NYALLKLAGDVESNPGPGSMNPAISVALLLSVLQVSRGQK 
               
               
                   
               
               
                   
                 VTSLTACLVNQNLRLDCRHENNTKDNSIQHEFSLTREKRK 
               
               
                   
               
               
                   
                 HVLSGTLGIPEHTYRSRVTLSNQPYIKVLTLANFTTKDEG 
               
               
                   
               
               
                   
                 DYFCELRVSGANPMSSNKSISVYRDKLVKCGGISLLVQNT 
               
               
                   
               
               
                   
                 SWMLLLLLSLSLLQALDFISL 
               
            
           
         
       
     
     In certain embodiments, the membrane-bound polypeptide comprises a V5 tag, an EE12RR345L leucine zipper, a IgG1 hinge, a CD28 costimulatory domain, a CD3ζ polypeptide, an E2A peptide, and a Thy1.1 polypeptide. (IgG1 hinge spacer. V5 tag staining identifies the membrane-bound polypeptide surface expression). In certain embodiments, the membrane-bound polypeptide comprises SEQ ID NO: 26. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 26] 
               
               
                   
                 METDTLLLWVLLLWVPGSTGGSGGKPIPNPLLGLDSTGGG 
               
               
                   
               
               
                   
                 GSGGGSLEIEAAFLERENTALETRVAELRQRVQRLRNRVS 
               
               
                   
               
               
                   
                 QYRTRYGPLGGGKAAAVPRDCGCKPCICTGSLIYIWAPLA 
               
               
                   
               
               
                   
                 GICVALLLSLIITLICYNSRRNRLLQSDYMNMTPRRPGLT 
               
               
                   
               
               
                   
                 RKPYQPYAPARDFAAYRPRAKFSRSAETAANLQDPNQLYN 
               
               
                   
               
               
                   
                 ELNLGRREEYDVLEKKRARDPEMGGKQQRRRNPQEGVYNA 
               
               
                   
               
               
                   
                 LQKDKMAEAYSEIGTKGERRRGKGHDGLYQGLSTATKDTY 
               
               
                   
               
               
                   
                 DALHMQTLAPRGTGQCTNYALLKLAGDVESNPGPGSMNPA 
               
               
                   
               
               
                   
                 ISVALLLSVLQVSRGQKVTSLTACLVNQNLRLDCRHENNT 
               
               
                   
               
               
                   
                 KDNSIQHEFSLTREKRKHVLSGTLGIPEHTYRSRVTLSNQ 
               
               
                   
               
               
                   
                 PYIKVLTLANFTTKDEGDYFCELRVSGANPMSSNKSISVY 
               
               
                   
               
               
                   
                 RDKLVKCGGISLLVQNTSWMLLLLLSLSLLQALDFISL 
               
            
           
         
       
     
     In certain embodiments, the membrane-bound polypeptide comprises a reverse tetracycline-controlled transactivator 3 (rtTA3), a P2A peptide, a V5 tag, an EE12RR345L leucine zipper, a IgG1 hinge, a CD28 costimulatory domain, a CD3ζ polypeptide, an E2A peptide, and a Thy1.1 polypeptide. (Tetracycline inducible ZipR-CAR with IgG1 hinge spacer; contains rtTA3 tetracycline inducible transactivator; ZipR scFv vector contains tetracycline response element tre3g sequence in self-inactivating retrovirus. V5 tag staining identifies the membrane-bound polypeptide surface expression). In certain embodiments, the membrane-bound polypeptide comprises SEQ ID NO: 27. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 27] 
               
               
                   
                 MSRLDKSKVINGALELLNGVGIEGLTTRKLAQKLGVEQPT 
               
               
                   
               
               
                   
                 LYWHVKNKRALLDALPIEMLDRHHTHFCPLEGESWQDFLR 
               
               
                   
               
               
                   
                 NNAKSYRCALLSHRDGAKVHLGTRPTEKQYETLENQLAFL 
               
               
                   
               
               
                   
                 CQQGFSLENALYALSAVGHFTLGCVLEEQEHQVAKEERET 
               
               
                   
               
               
                   
                 PTTDSMPPLLRQAIELFDRQGAEPAFLFGLELIICGLEKQ 
               
               
                   
               
               
                   
                 LKCESGGPTDALDDFDLDMLPADALDDFDLDMLPGGSGAT 
               
               
                   
               
               
                   
                 NFSLLKQAGDVEENPGPEFTMETDTLLLWVLLLWVPGSTG 
               
               
                   
               
               
                   
                 GSGGKPIPNPLLGLDSTGGGGSGGGSLEIEAAFLERENTA 
               
               
                   
               
               
                   
                 LETRVAELRQRVQRLRNRVSQYRTRYGPLGGGKAAAVPRD 
               
               
                   
               
               
                   
                 CGCKPCICTGSLIYIWAPLAGICVALLLSLIITLICYNSR 
               
               
                   
               
               
                   
                 RNRLLQSDYMNMTPRRPGLTRKPYQPYAPARDFAAYRPRA 
               
               
                   
               
               
                   
                 KFSRSAETAANLQDPNQLYNELNLGRREEYDVLEKKRARD 
               
               
                   
               
               
                   
                 PEMGGKQQRRRNPQEGVYNALQKDKMAEAYSEIGTKGERR 
               
               
                   
               
               
                   
                 RGKGHDGLYQGLSTATKDTYDALHMQTLAPRGTGQCTNYA 
               
               
                   
               
               
                   
                 LLKLAGDVESNPGPGSMNPAISVALLLSVLQVSRGQKVTS 
               
               
                   
               
               
                   
                 LTACLVNQNLRLDCRHENNTKDNSIQHEFSLTREKRKHVL 
               
               
                   
               
               
                   
                 SGTLGIPEHTYRSRVTLSNQPYIKVLTLANFTTKDEGDYF 
               
               
                   
               
               
                   
                 CELRVSGANPMSSNKSISVYRDKLVKCGGISLLVQNTSWM 
               
               
                   
               
               
                   
                 LLLLLSLSLLQALDFISL 
               
            
           
         
       
     
     In certain embodiments, the membrane-bound polypeptide comprises an EE12RR345L leucine zipper, a myc tag, an CD8EC hinge, a CD28 costimulatory domain, a CD3ζ polypeptide, an E2A peptide, and a Thy1.1 polypeptide. (CD8 spacer; positive myc staining). In certain embodiments, the membrane-bound polypeptide comprises SEQ ID NO: 28. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 28] 
               
               
                   
                 METDTLLLWVLLLWVPGSTGLETEAAFLERENTALETRVA 
               
               
                   
               
               
                   
                 ELRQRVQRLRNRVSQYRTRYGPLGGGKGSGEQKLISEEDL 
               
               
                   
               
               
                   
                 AAASTTTKPVLRTPSPVHPTGTSQPQRPEDCRPRGSVKGT 
               
               
                   
               
               
                   
                 GLDFACDIYIWAPLAGICVALLLSLIITLICYNSRRNRLL 
               
               
                   
               
               
                   
                 QSDYMNMTPRRPGLTRKPYQPYAPARDFAAYRPRAKFSRS 
               
               
                   
               
               
                   
                 AETAANLQDPNQLYNELNLGRREEYDVLEKKRARDPEMGG 
               
               
                   
               
               
                   
                 KQQRRRNPQEGVYNALQKDKMAEAYSEIGTKGERRRGKGH 
               
               
                   
               
               
                   
                 DGLYQGLSTATKDTYDALHMQTLAPRGTGQCTNYALLKLA 
               
               
                   
               
               
                   
                 GDVESNPGPGSMNPAISVALLLSVLQVSRGQKVTSLTACL 
               
               
                   
               
               
                   
                 VNQNLRLDCRHENNTKDNSIQHEFSLTREKRKHVLSGTLG 
               
               
                   
               
               
                   
                 IPEHTYRSRVTLSNQPYIKVLTLANFTTKDEGDYFCELRV 
               
               
                   
               
               
                   
                 SGANPMSSNKSISVYRDKLVKCGGISLLVQNTSWMLLLLL 
               
               
                   
               
               
                   
                 SLSLLQALDFISL 
               
            
           
         
       
     
     In certain embodiments, the soluble polypeptide comprises a CD19 scFv, a FLAG tag, a RR12EE345L leucine zipper, a T2A peptide, and a blue fluorescent protein (BFP). In certain embodiments, the soluble polypeptide comprises SEQ ID NO: 29. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 29] 
               
               
                   
                 EFTDYKDDDDKLEIRAAFLRQRNTALRTEVAELEQEVQRL 
               
               
                   
               
               
                   
                 ENEVSQYETRYGPLGGGKGSGRAKRATNFSLLKQAGDVEE 
               
               
                   
               
               
                   
                 NPGPTRTGLESMSELIKENMHMKLYMEGTVDNHHFKCTSE 
               
               
                   
               
               
                   
                 GEGKPYEGTQTMRIKVVEGGPLPFAFDILATSFLYGSKTF 
               
               
                   
               
               
                   
                 INHTQGIPDFFKQSFPEGFTWERVTTYEDGGVLTATQDTS 
               
               
                   
               
               
                   
                 LQDGCLIYNVKIRGVNFTSNGPVMQKKTLGWEAFTETLYP 
               
               
                   
               
               
                   
                 ADGGLEGRNDMALKLVGGSHLIANIKTTYRSKKPAKNLKM 
               
               
                   
               
               
                   
                 PGVYYVDYRLERIKEANNETYVEQHEVAVARYCDLPSKLG 
               
               
                   
               
               
                   
                 HKLN 
               
            
           
         
       
     
     In certain embodiments, the system comprises a CD19 scFv, a FLAG tag, a RR12EE345L leucine zipper, a P2A peptide, a CD20 scFv, a second FLAG tag, a second RR12EE345L leucine zipper, a T2A peptide, and a blue fluorescent protein (BFP). In certain embodiments, the system comprises SEQ ID NO: 30 and 31. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 30] 
               
               
                   
                 EFTDYKDDDDKLEIRAAFLRQRNTALRTEVAELEQEVQRL 
               
               
                   
               
               
                   
                 ENEVSQYETRYGPLGGGKGSGRAKRATNFSLLKQAGDVE 
               
               
                   
               
               
                   
                 ENPGPTRT 
               
               
                   
               
               
                   
                 [SEQ ID NO: 31] 
               
               
                   
                 RSGDYKDDDDKLEIRAAFLRQRNTALRTEVAELEQEVQR 
               
               
                   
               
               
                   
                 LENEVSQYETRYGPLGGGKGSGGSGRAKRQCTNYALLKL 
               
               
                   
               
               
                   
                 AGDVESNPGPGSLGSGLESMSELIKENMHMKLYMEGTVD 
               
               
                   
               
               
                   
                 NHHFKCTSEGEGKPYEGTQTMRIKVVEGGPLPFAFDILA 
               
               
                   
               
               
                   
                 TSFLYGSKTFINHTQGIPDFFKQSFPEGFTWERVTTYED 
               
               
                   
               
               
                   
                 GGVLTATQDTSLQDGCLIYNVKIRGVNFTSNGPVMQKKT 
               
               
                   
               
               
                   
                 LGWEAFTETLYPADGGLEGRNDMALKLVGGSHLIANIKT 
               
               
                   
               
               
                   
                 TYRSKKPAKNLKMPGVYYVDYRLERIKEANNETYVEQHE 
               
               
                   
               
               
                   
                 VAVARYCDLPSKLGHKLN 
               
            
           
         
       
     
     In certain embodiments, the system comprises a CD19 scFv, a FLAG tag, a RR12EE345L leucine zipper, a P2A peptide, a CD20 scFv, a second FLAG tag, a second RR12EE345L leucine zipper, an E2A peptide, an IL-3 polypeptide, a third FLAG tag, a third RR12EE345L leucine zipper, a T2A peptide, and a blue fluorescent protein (BFP). In certain embodiments, the system comprises SEQ ID NO: 32 and 33. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 32] 
               
               
                   
                 EFTDYKDDDDKLEIRAAFLRQRNTALRTEVAELEQEVQRL 
               
               
                   
               
               
                   
                 ENEVSQYETRYGPLGGGKGSGRAKRATNFSLLKQAGDVEE 
               
               
                   
               
               
                   
                 NPGPTRT 
               
               
                   
               
               
                   
                 [SEQ ID NO: 33] 
               
               
                   
                 RSGDYKDDDDKLEIRAAFLRQRNTALRTEVAELEQEVQRL 
               
               
                   
               
               
                   
                 ENEVSQYETRYGPLGGGKGSGGSGRAKRQCTNYALLKLAG 
               
               
                   
               
               
                   
                 DVESNPGPGSLMVLASSTTSIHTMLLLLLMLFHLGLQASI 
               
               
                   
               
               
                   
                 SGRDTHRLTRTLNCSSIVKETIGKLPEPELKTDDEGPSLR 
               
               
                   
               
               
                   
                 NKSFRRVNLSKFVESQGEVDPEDRYVIKSNLQKLNCCLPT 
               
               
                   
               
               
                   
                 SANDSALPGVFIRDLDDERKKLRFYMVHLNDLETVLTSRP 
               
               
                   
               
               
                   
                 PQPASGSVSPNRGTVECGSGDYKDDDDKLEIRAAFLRQRN 
               
               
                   
               
               
                   
                 TALRTEVAELEQEVQRLENEVSQYETRYGPLGGGKGSGRA 
               
               
                   
               
               
                   
                 KREGRGSLLTCGDVEENPGPLESMSELIKENMHMKLYMEG 
               
               
                   
               
               
                   
                 TVDNHHEKCTSEGEGKPYEGTQTMRIKVVEGGPLPFAFDI 
               
               
                   
               
               
                   
                 LATSFLYGSKTFINHTQGIPDFFKQSFPEGFTWERVTTYE 
               
               
                   
               
               
                   
                 DGGVLTATQDTSLQDGCLIYNVKIRGVNFTSNGPVMQKKT 
               
               
                   
               
               
                   
                 LGWEAFTETLYPADGGLEGRNDMALKLVGGSHLIANIKTT 
               
               
                   
               
               
                   
                 YRSKKPAKNLKMPGVYYVDYRLERIKEANNETYVEQHEVA 
               
               
                   
               
               
                   
                 VARYCDLPSKLGHKLN 
               
            
           
         
       
     
     In certain embodiments, the soluble polypeptide comprises a mouse IL-7 polypeptide fused to FLAG-tagged RR12EE345L leucine zipper, an E2A peptide, and a blue fluorescent protein (BFP). In certain embodiments, the soluble polypeptide comprises SEQ ID NO: 34. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 34] 
               
               
                   
                 MFHVSFRYIFGIPPLILVLLPVTSSECHIKDKEGKAYESV 
               
               
                   
               
               
                   
                 LMISIDELDKMTGTDSNCPNNEPNFFRKHVCDDTKEAAFL 
               
               
                   
               
               
                   
                 NRAARKLKQFLKMNISEEFNVHLLTVSQGTQTLVNCTSKE 
               
               
                   
               
               
                   
                 EKNVKEQKKNDACFLKRLLREIKTCWNKILKGSIEFTDYK 
               
               
                   
               
               
                   
                 DDDDKLEIRAAFLRQRNTALRTEVAELEQEVQRLENEVSQ 
               
               
                   
               
               
                   
                 YETRYGPLGGGKGSGRAKRATNFSLLKQAGDVEENPGPTR 
               
               
                   
               
               
                   
                 TGLESMSELIKENMHMKLYMEGTVDNHHFKCTSEGEGKPY 
               
               
                   
               
               
                   
                 EGTQTMRIKVVEGGPLPFAFDILATSFLYGSKTFINHTQG 
               
               
                   
               
               
                   
                 IPDFFKQSFPEGFTWERVTTYEDGGVLTATQDTSLQDGCL 
               
               
                   
               
               
                   
                 IYNVKIRGVNFTSNGPVMQKKTLGWEAFTETLYPADGGLE 
               
               
                   
               
               
                   
                 GRNDMALKLVGGSHLIANIKTTYRSKKPAKNLKMPGVYYV 
               
               
                   
               
               
                   
                 DYRLERIKEANNETYVEQHEVAVARYCDLPSKLGHKLN 
               
            
           
         
       
     
     In certain embodiments, the soluble polypeptide comprises a mouse IL-15 polypeptide, fused to FLAG-tagged RR12EE345L leucine zipper, an E2A peptide, and a blue fluorescent protein (BFP), and comprises a mouse IL-2 signal peptide. In certain embodiments, the soluble polypeptide comprises SEO ID NO: 35. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 35] 
               
               
                   
                 MYSMQLASCVTLTLVLLVNSNWIDVRYDLEKIESLIQSIH 
               
               
                   
               
               
                   
                 IDTTLYTDSDFHPSCKVTAMNCFLLELQVILHEYSNMTLN 
               
               
                   
               
               
                   
                 ETVRNVLYLANSTLSSNKNVAESGCKECEELEEKTFTEFL 
               
               
                   
               
               
                   
                 QSFIRIVQMFINTSRSGDYKDDDDKLEIRAAFLRQRNTAL 
               
               
                   
               
               
                   
                 RTEVAELEQEVQRLENEVSQYETRYGPLGGGKGSGGSGRA 
               
               
                   
               
               
                   
                 KRQCTNYALLKLAGDVESNPGPGSLGSGLESMSELIKENM 
               
               
                   
               
               
                   
                 HMKLYMEGTVDNHHFKCTSEGEGKPYEGTQTMRIKVVEGG 
               
               
                   
               
               
                   
                 PLPFAFDILATSFLYGSKTFINHTQGIPDFFKQSFPEGFT 
               
               
                   
               
               
                   
                 WERVTTYEDGGVLTATQDTSLQDGCLIYNVKIRGVNFTSN 
               
               
                   
               
               
                   
                 GPVMQKKTLGWEAFTETLYPADGGLEGRNDMALKLVGGSH 
               
               
                   
               
               
                   
                 LIANIKTTYRSKKPAKNLKMPGVYYVDYRLERIKEANNET 
               
               
                   
               
               
                   
                 YVEQHEVAVARYCDLPSKLGHKLN 
               
            
           
         
       
     
     In certain embodiments, the soluble polypeptide comprises a mouse IL-21 polypeptide fused to FLAG-tagged RR12EE345L leucine zipper, an E2A peptide, and a blue fluorescent protein (BFP). In certain embodiments, the soluble polypeptide comprises SEQ ID NO: 36. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 36] 
               
               
                   
                 MERTLVCLVVIFLGTVAHKSSPQGPBRLLIRLRHLIDIVE 
               
               
                   
               
               
                   
                 QLKIYENBLBPELLSAPQBVKGHCEHAAFACFQKAKLKPS 
               
               
                   
               
               
                   
                 NPGNNKTFIIDLVAQLRRRLPARRGGKKQKHIAKCPSCDS 
               
               
                   
               
               
                   
                 YEKRTPKEFLERLKWLLQKMIHQHLSEFTDYKDDDDKLEI 
               
               
                   
               
               
                   
                 RAAFLRQRNTALRTEVAELEQEVQRLENEVSQYETRYGPL 
               
               
                   
               
               
                   
                 GGGKGSGRAKRATNFSLLKQAGDVEENPGPTRTGLESMSE 
               
               
                   
               
               
                   
                 LIKENMHMKLYMEGTVDNHHFKCTSEGEGKPYEGTQTMRI 
               
               
                   
               
               
                   
                 KVVEGGPLPFAFDILATSFLYGSKTFINHTQGIPDFFKQS 
               
               
                   
               
               
                   
                 FPEGFTWERVTTYEDGGVLTATQDTSLQDGCLIYNVKIRG 
               
               
                   
               
               
                   
                 VNFTSNGPVMQKKTLGWEAFTETLYPADGGLEGRNDMALK 
               
               
                   
               
               
                   
                 LVGGSHLIANIKTTYRSKKPAKNLKMPGVYYVDYRLERIK 
               
               
                   
               
               
                   
                 EANNETYVEQHEVAVARYCDLPSKLGHKLN 
               
            
           
         
       
     
     In certain embodiments, the soluble polypeptide comprises a mouse IL-21 polypeptide fused to FLAG-tagged RR12EE345L leucine zipper, an E2A peptide, and a blue fluorescent protein (BFP), and comprises a mouse IL-2 signal peptide. In certain embodiments, the soluble polypeptide comprises SEQ ID NO: 37. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 37] 
               
               
                   
                 MYSMQLASCVTLTLVLLVNSHKSSPQGPDRLLIRLRHLID 
               
               
                   
               
               
                   
                 IVEQLKIYENDLDPELLSAPQDVKGHCEHAAFACFQKAKL 
               
               
                   
               
               
                   
                 KPSNPGNNKTFIIDLVAQLRRRLPARRGGKKQKHIAKCPS 
               
               
                   
               
               
                   
                 CDSYEKRTPKEFLERLKWLLQKMIHQHLSGGGGSGGGSEF 
               
               
                   
               
               
                   
                 TDYKDDDDKLEIRAAFLRQRNTALRTEVAELEQEVQRLEN 
               
               
                   
               
               
                   
                 EVSQYETRYGPLGGGKGSGRAKRATNFSLLKQAGDVEENP 
               
               
                   
               
               
                   
                 GPTRTGLESMSELIKENMHMKLYMEGTVDNHHFKCTSEGE 
               
               
                   
               
               
                   
                 GKPYEGTQTMRIKVVEGGPLPFAFDILATSFLYGSKTFIN 
               
               
                   
               
               
                   
                 HTQGIPDFFKQSFPEGFTWERVTTYEDGGVLTATQDTSLQ 
               
               
                   
               
               
                   
                 DGCLIYNVKIRGVNFTSNGPVMQKKTLGWEAFTETLYPAD 
               
               
                   
               
               
                   
                 GGLEGRNDMALKLVGGSHLIANIKTTYRSKKPAKNLKMPG 
               
               
                   
               
               
                   
                 VYYVDYRLERIKEANNETYVEQHEVAVARYCDLPSKLGHK 
               
               
                   
               
               
                   
                 LN 
               
            
           
         
       
     
     In certain embodiments, the system comprises a mouse IL-7 polypeptide, a RR12EE345L leucine zipper, a FLAG tag, a P2A peptide, an sIL-15 polypeptide, a second FLAG tag, a second RR12EE345L leucine zipper, an E2A peptide, and a blue fluorescent protein (BFP). In certain embodiments, the system comprises SEQ ID NO: 38. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 38] 
               
               
                   
                 MFHVSFRYIFGIPPLILVLLPVTSSECHIKDKEGKAYESV 
               
               
                   
               
               
                   
                 LMISIDELDKMTGTDSNCPNNEPNFFRKHVCDDTKEAAFL 
               
               
                   
               
               
                   
                 NRAARKLKQFLKMNISEEFNVHLLTVSQGTQTLVNCTSKE 
               
               
                   
               
               
                   
                 EKNVKEQKKNDACFLKRLLREIKTCWNKILKGSIEFTDYK 
               
               
                   
               
               
                   
                 DDDDKLEIRAAFLRQRNTALRTEVAELEQEVQRLENEVSQ 
               
               
                   
               
               
                   
                 YETRYGPLGGGKGSGRAKRATNFSLLKQAGDVEENPGPTR 
               
               
                   
               
               
                   
                 TMYSMQLASCVTLTLVLLVNSNWIDVRYDLEKIESLIQSI 
               
               
                   
               
               
                   
                 HIDTTLYTDSDFHPSCKVTAMNCFLLELQVILHEYSNMTL 
               
               
                   
               
               
                   
                 NETVRNVLYLANSTLSSNKNVAESGCKECEELEEKTFTEF 
               
               
                   
               
               
                   
                 LQSFIRIVQMFINTSRSGDYKDDDDKLEIRAAFLRQRNTA 
               
               
                   
               
               
                   
                 LRTEVAELEQEVQRLENEVSQYETRYGPLGGGKGSGGSGR 
               
               
                   
               
               
                   
                 AKRQCTNYALLKLAGDVESNPGPGSLGSGLESMSELIKEN 
               
               
                   
               
               
                   
                 MHMKLYMEGTVDNHHFKCTSEGEGKPYEGTQTMRIKVVEG 
               
               
                   
               
               
                   
                 GPLPFAFDILATSFLYGSKTFINHTQGIPDFFKQSFPEGF 
               
               
                   
               
               
                   
                 TWERVTTYEDGGVLTATQDTSLQDGCLIYNVKIRGVNFTS 
               
               
                   
               
               
                   
                 NGPVMQKKTLGWEAFTETLYPADGGLEGRNDMALKLVGGS 
               
               
                   
               
               
                   
                 HLIANIKTTYRSKKPAKNLKMPGVYYVDYRLERIKEANNE 
               
               
                   
               
               
                   
                 TYVEQHEVAVARYCDLPSKLGHKLN 
               
            
           
         
       
     
     In certain embodiments, the soluble polypeptide comprises a CCL1 polypeptide fused to a FLAG-tagged RR12EE345L leucine zipper. In certain embodiments, the soluble polypeptide comprises SEQ ID NO: 87. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 87] 
               
               
                   
                 MASPLTRELSLNLLLLGESTILGSGEAKSMLTVSNSCCLN 
               
               
                   
               
               
                   
                 TLKKELPLKFIQCYRKMGSSCPDPPAVVERLNKGRESCAS 
               
               
                   
               
               
                   
                 TNKTWVQNHLKKVNPCSGGGGSDPEFTDYKDDDDKLEIRA 
               
               
                   
               
               
                   
                 AFLRQRNTALRTEVAELEQEVQRLENEVSQYETRYGPLGG 
               
               
                   
               
               
                   
                 GK 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 87 is set forth in SEQ ID NO: 88, which is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 88] 
               
               
                   
                 ATGGCCTCACCGTTGACCCGCTTTCTGTCGCTGAACCTGC 
               
               
                   
               
               
                   
                 TGCTGCTGGGTGAGTCGATTATCCTGGGGAGTGGAGAAGC 
               
               
                   
               
               
                   
                 TAAGAGCATGCTTACGGTCTCCAATAGCTGCTGCTTGAAC 
               
               
                   
               
               
                   
                 ACCTTGAAGAAAGAGCTTCCCCTGAAGTTTATCCAGTGTT 
               
               
                   
               
               
                   
                 ACAGAAAGATGGGCTCCTCCTGTCCTGATCCCCCAGCTGT 
               
               
                   
               
               
                   
                 GGTATTCAGGCTGAACAAAGGTAGAGAAAGCTGCGCCTCA 
               
               
                   
               
               
                   
                 ACTAACAAAACGTGGGTTCAAAATCACCTGAAGAAGGTGA 
               
               
                   
               
               
                   
                 ACCCCTGCAGCGGCGGGGGTGGCAGCGACCCCGAATTCAC 
               
               
                   
               
               
                   
                 CGATTACAAGGACGACGATGACAAGCTGGAGATCCGCGCT 
               
               
                   
               
               
                   
                 GCATTTTTGCGACAAAGAAATACCGCTTTGCGAACCGAAG 
               
               
                   
               
               
                   
                 TGGCCGAGTTGGAGCAGGAAGTACAACGCCTGGAAAATGA 
               
               
                   
               
               
                   
                 AGTCAGCCAATACGAAACTCGATATGGACCTCTCGGAGGT 
               
               
                   
               
               
                   
                 GGAAAG 
               
            
           
         
       
     
     In certain embodiments, the soluble polypeptide comprises a CCL17 polypeptide fused to a FLAG-tagged RR12EE345L leucine zipper. In certain embodiments, the soluble polypeptide comprises SEQ ID NO: 89. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 89] 
               
               
                   
                 MASPLTRFLSLNLLLLGESIILGSGEAARATNVGRECCLD 
               
               
                   
               
               
                   
                 YFKGAIPIRKLVSWYKTSVECSRDAIVFLTVQGKLICADP 
               
               
                   
               
               
                   
                 KDKHVKKAIRLVKNPRPSGGGGSDPEFTDYKDDDDKLEIR 
               
               
                   
               
               
                   
                 AAFLRQRNTALRTEVAELEQEVQRLENEVSQYETRYGPLG 
               
               
                   
               
               
                   
                 GGK 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 89 is set forth in SEQ ID NO: 90, which is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 90] 
               
               
                   
                 ATGGCCTCACCGTTGACCCGCTTTCTGTCGCTGAACCTGC 
               
               
                   
               
               
                   
                 TGCTGCTGGGTGAGTCGATTATCCTGGGGAGTGGAGAAGC 
               
               
                   
               
               
                   
                 CGCCCGAGCCACCAATGTAGGCCGAGAGTGCTGCCTGGAT 
               
               
                   
               
               
                   
                 TACTTCAAAGGGGCCATTCCTATCAGGAAGTTGGTGAGCT 
               
               
                   
               
               
                   
                 GGTATAAGACCTCAGTGGAGTGTTCCAGGGATGCCATCGT 
               
               
                   
               
               
                   
                 GTTTCTGACTGTCCAGGGCAAGCTCATCTGTGCAGACCCC 
               
               
                   
               
               
                   
                 AAAGACAAACATGTGAAGAAGGCCATCAGATTGGTGAAAA 
               
               
                   
               
               
                   
                 ACCCAAGGCCAAGCGGCGGGGGTGGCAGCGACCCCGAATT 
               
               
                   
               
               
                   
                 CACCGATTACAAGGACGACGATGACAAGCTGGAGATCCGC 
               
               
                   
               
               
                   
                 GCTGCATTTTTGCGACAAAGAAATACCGCTTTGCGAACCG 
               
               
                   
               
               
                   
                 AAGTGGCCGAGTTGGAGCAGGAAGTACAACGCCTGGAAAA 
               
               
                   
               
               
                   
                 TGAAGTCAGCCAATACGAAACTCGATATGGACCTCTCGGA 
               
               
                   
               
               
                   
                 GGTGGAAAG 
               
            
           
         
       
     
     In certain embodiments, the soluble polypeptide comprises a CCL22 polypeptide fused to a FLAG-tagged RR12EE345L leucine zipper. In certain embodiments, the soluble polypeptide comprises SEQ ID NO: 91. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 91] 
               
               
                   
                 MASPLTRFLSLNLLLLGESIILGSGEAGPYGANVEDSICC 
               
               
                   
               
               
                   
                 QDYIRHPLPSRLVKEFFWISKSCRKPGVVLITVKNRDICA 
               
               
                   
               
               
                   
                 DPRQVWVKKLLHKLSSGGGGSDPEFTDYKDDDDKLEIRAA 
               
               
                   
               
               
                   
                 FLRQRNTALRIEVAELEQEVQRLENEVSQYETRYGPLGGG 
               
               
                   
               
               
                   
                 K 
               
            
           
         
       
     
     An exemplary nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 91 is set forth in SEQ ID NO: 92, which is provided below. 
     
       
         
           
               
               
            
               
                   
                 [SEQ ID NO: 92] 
               
               
                   
                 ATGGCCTCACCGTTGACCCGCTTTCTGTCGCTGAACCTGC 
               
               
                   
               
               
                   
                 TGCTGCTGGGTGAGTCGATTATCCTGGGGAGTGGAGAAGC 
               
               
                   
               
               
                   
                 CGGTCCCTATGGTGCCAATGTGGAAGACAGTATCTGCTGC 
               
               
                   
               
               
                   
                 CAGGACTACATCCGTCACCCTCTGCCATCACGTTTAGTGA 
               
               
                   
               
               
                   
                 AGGAGTTCTTCTGGACCTCAAAATCCTGCCGCAAGCCTGG 
               
               
                   
               
               
                   
                 CGTTGTTTTGATAACCGTCAAGAACCGAGATATCTGTGCC 
               
               
                   
               
               
                   
                 GATCCCAGGCAGGTCTGGGTGAAGAAGCTACTCCATAAAC 
               
               
                   
               
               
                   
                 TGTCCAGCGGCGGGGGTGGCAGCGACCCCGAATTCACCGA 
               
               
                   
               
               
                   
                 TTACAAGGACGACGATGACAAGCTGGAGATCCGCGCTGCA 
               
               
                   
               
               
                   
                 TTTTTGCGACAAAGAAATACCGCTTTGCGAACCGAAGTGG 
               
               
                   
               
               
                   
                 CCGAGTTGGAGCAGGAAGTACAACGCCTGGAAAATGAAGT 
               
               
                   
               
               
                   
                 CAGCCAATACGAAACTCGATATGGACCTCTCGGAGGTGGA 
               
               
                   
               
               
                   
                 AAG 
               
            
           
         
       
     
     Exemplary sequences of the elements comprised in a leucine zipper construct are as follows. 
     Interchain linker: SGGGGSDPEFT [SEQ ID NO: 93] 
     2A Peptide Sequences: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                   
                 E2A 
                 QCTNYALLKLAGDVESNPGP 
               
               
                   
                   
                 [SEQ ID NO: 39] 
               
               
                   
               
               
                   
                 F2A 
                 VKQTLNFDLLKLAGDVESNPGP 
               
               
                   
                   
                 [SEQ ID NO: 40] 
               
               
                   
               
               
                   
                 P2A 
                 ATNFSLLKQAGDVEENPGP 
               
               
                   
                   
                 [SEQ ID NO: 41] 
               
               
                   
               
               
                   
                 T2A 
                 EGRGSLLTCGDVEENPGP 
               
               
                   
                   
                 [SEQ ID NO: 42] 
               
               
                   
               
            
           
         
       
     
     Tag Sequences: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                   
                 FLAG 
                 DYKDDDDK 
               
               
                   
                   
                 [SEQ ID NO: 43] 
               
               
                   
               
               
                   
                 Myc 
                 EQKLISEEDL 
               
               
                   
                   
                 [SEQ ID NO: 44] 
               
               
                   
               
               
                   
                 V5 
                 GKPIPNPLLGLDST GGGGSGGGS   
               
               
                   
                 (additional 
                 [SEQ ID NO: 45] 
               
               
                   
                 linker 
                   
               
               
                   
                 underlined) 
               
               
                   
               
            
           
         
       
     
     Signal Peptide Sequences: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                   
                 Mouse kappa 
                 METDTLLLWVLLLWVPGSTG 
               
               
                   
                 leader 
                 [SEQ ID NO: 46] 
               
               
                   
               
               
                   
                 Mouse CD8 
                 MASPLTRFLSLNLLLLGESIILGSGEA 
               
               
                   
                 alpha 
                 [SEQ ID NO: 47] 
               
               
                   
               
               
                   
                 Mouse IL-2 
                 MYSMQLASCVTLTLVLLVNS 
               
               
                   
                   
                 [SEQ ID NO: 48] 
               
               
                   
               
               
                   
                 Mouse IL-3 
                 MVLASSITSIHTMLLLLLMLFHLGLQ 
               
               
                   
                   
                 [SEQ ID NO: 49] 
               
               
                   
               
               
                   
                 Mouse IL-7 
                 MFHVSFRYIFGIPPLILVLLPVISS 
               
               
                   
                   
                 [SEQ ID NO: 50] 
               
               
                   
               
               
                   
                 Mouse IL-21 
                 MERTLVCLVVIFLGTVA 
               
               
                   
                   
                 [SEQ ID NO: 51] 
               
               
                   
               
            
           
         
       
     
     Additional Sequences: 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 tagBFP 
                 MSELIKENMHMKLYMEGTVDNHHFKCTSEGEGKPY 
               
               
                 (Addgene 
                 EGTQTMRIKVVEGGPLPFAFDILATSFLYGSKTFI 
               
               
                 11240) 
                 NHTQGIPDFFKQSFPEGFTWERVTTYEDGGVLTAT 
               
               
                   
                 QDTSLQDGCLIYNVKIRGVNFTSNGPVMQKKTLGW 
               
               
                   
                 EAFTETLYPADGGLEGRNDMALKLVGGSHLIANIK 
               
               
                   
                 TTYRSKKPAKNLKMPGVYYVDYRLERIKEANNETY 
               
               
                   
                 VEQHEVAVARYCDLPSKLGHKLN 
               
               
                   
                 [SEQ ID NO: 52] 
               
               
                   
               
               
                 rtTA3 
                 MSRLDKSKVINGALELLNGVGIEGLTTRKLAQKLG 
               
               
                 (Addgene 
                 VEQPTLYWHVKNKRALLDALPIEMLDRHHTHFCPL 
               
               
                 68449) 
                 EGESWQDFLRNNAKSYRCALLSHRDGAKVHLGTRP 
               
               
                   
                 TEKQYETLENQLAFLCQQGFSLENALYALSAVGHF 
               
               
                   
                 TLGCVLEEQEHQVAKEERETPTTDSMPPLLRQATE 
               
               
                   
                 LFDRQGAEPAELFGLELIICGLEKQLKCESGGPTD 
               
               
                   
                 ALDDFDLDMLPADALDDFDLDMLPG 
               
               
                   
                 [SEQ ID NO: 53] 
               
               
                   
               
               
                 Mouse IL-3 
                 MVLASSTTSIHTMLLLLLMLFHLGLQ ASISGRDTH   
               
               
                 (mature 
                 
                   RLTRTLNCSSIVKETIGKLPEPELKTDDEGPSLRN 
                 
               
               
                 peptide 
                 
                   KSFRRVNLSKFVESQGEVDPEDRYVIKSNLQKLNC 
                 
               
               
                 underlined, 
                 
                   CLPTSANDSALPGVFIRDLDDERKKLRFYMVHLND 
                 
               
               
                 Uniprot 
                 
                   LETVLTSRPPQPASGSVSPNRGTVEC 
                 
               
               
                 P01586) 
                 [SEQ ID NO: 54] 
               
               
                   
               
               
                 Mouse IL-7 
                 MFHVSFRYIEGIPPLILVLLPVTSS ECHIKDKEGK   
               
               
                 (mature 
                 
                   AYESVLMISIDELDKMTGTDSNCPNNEPNFERKHV 
                 
               
               
                 peptide 
                 
                   CDDTKEAAFLNRAARKLKULKMNISEEENVHLLTV 
                 
               
               
                 underlined, 
                 
                   SQGTQTLVNCTSKEEKNVKEQKKNDACFLKRLLRE 
                 
               
               
                 Uniprot 
                 
                   IKTCWNKILKGSI 
                 
               
               
                 P10168) 
                 [SEQ ID NO: 55] 
               
               
                   
               
               
                 Mouse IL-15 
                 MKILKPYMRNTSISCYLCFLLNSHFLTEAGIHVFI 
               
               
                 (mature 
                 LGCVSVGLPKTEA NWIDVRYDLEKIESLIQSIHID   
               
               
                 peptide 
                 
                   TTLYTDSDFHPSCKVTAMNCELLELQVILHEYSNM 
                 
               
               
                 underlined, 
                 
                   ILNETVRNVLYLANSTLSSNKNVAESGCKECEELE 
                 
               
               
                 Uniprot 
                 
                   EKTFTEFLQSFIRIVQMFINTS 
                 
               
               
                 P48346) 
                 [SEQ ID NO: 56] 
               
               
                   
               
               
                 Mouse IL-21 
                 MERTLVCLVVIFLGTVA HKSSPQGPDRLLIRLRHL   
               
               
                 (mature 
                 
                   IDIVEQLKIYENDLDPELLSAPQDVKGHCEHAAFA 
                 
               
               
                 peptide 
                 
                   CFQKAKLKPSNPGNNKTFIIDLVAQLRRRLPARRG 
                 
               
               
                 underlined, 
                 
                   GKKQKHIAKCPSCDSYEKRTPKEFLERLKWLLQKM 
                 
               
               
                 Uniprot 
                 
                   IHQHLS 
                 
               
               
                 Q9ES17) 
                 [SEQ ID NO: 57] 
               
               
                   
               
            
           
         
       
     
     4. Cells 
     The presently disclosed subject matter provides cells comprising a membrane-bound polypeptide, a soluble polypeptide and/or a system disclosed herein. In certain embodiments, the polypeptides and/or the system are capable of activating or inhibiting an immunoresponsive cell. In certain embodiments, the polypeptides and/or the system are capable of promoting an anti-tumor effect of an immunoresponsive cell. The cells can be transduced with the polypeptides and/or the systems such that the cells co-express the polypeptides and/or the system. In certain embodiments, the cell is an immunoresponsive cell. The cell can be a cell of the lymphoid lineage or a myeloid lineage. 
     Cells of the lymphoid lineage can produce antibodies, regulate the cellular immune system, detect foreign agents in the blood, and detect cells foreign to the host, and the like. Non-limiting examples of cells of the lymphoid lineage include T cells, B cells, dendric cells, Natural Killer (NK) cells, cells from which lymphoid cells may be differentiated. In certain embodiments, the stem cell is a pluripotent stem cell. In certain embodiments, the pluripotent stem cell is an embryonic stem cell or an induced pluripotent stem cell. 
     In certain embodiments, the cell is a T cell. T cells can be lymphocytes that mature in the thymus and are chiefly responsible for cell-mediated immunity. T cells are involved in the adaptive immune system. The T cells of the presently disclosed subject matter can be any type of T cells, including, but not limited to, helper T cells, cytotoxic T cells, memory T cells (including central memory T cells, stem-cell-like memory T cells (or stem-like memory T cells), and two types of effector memory T cells: e.g., TEM cells and TEMRA cells, Regulatory T cells (also known as suppressor T cells), Natural killer T cells, Mucosal associated invariant T cells, and γδ T cells. Cytotoxic T cells (CTL or killer T cells) are a subset of T lymphocytes capable of inducing the death of infected somatic or tumor cells. A patient&#39;s own T cells may be genetically modified to target specific antigens through the introduction of any polypeptide or system disclosed herein. The T cell can be a CD4 +  T cell or a CD8 +  T cell. In certain embodiments, the T cell is a CD4 +  T cell. In certain embodiments, the T cell is a CD8 +  T cell. 
     In certain embodiments, the cell is a Natural killer cell. Natural killer (NK) cells can be lymphocytes that are part of cell-mediated immunity and act during the innate immune response. NK cells do not require prior activation in order to perform their cytotoxic effect on target cells. 
     In certain embodiments, the cells are human lymphocytes. In certain embodiments, the human lymphocytes comprise without limitation, peripheral donor lymphocytes, e.g., those disclosed in Sadelain, M., et al. 2003  Nat Rev Cancer  3:35-45 (disclosing peripheral donor lymphocytes genetically modified to express CARs), in Morgan, R. A., et al. 2006  Science  314:126-129 (disclosing peripheral donor lymphocytes genetically modified to express a full-length tumor antigen-recognizing T cell receptor complex comprising the α and β heterodimer), in Panelli, M. C., et al. 2000  J Immunol  164:495-504; Panelli, M. C., et al. 2000  J Immunol  164:4382-4392 (disclosing lymphocyte cultures derived from tumor infiltrating lymphocytes (TILs) in tumor biopsies), and in Dupont, J., et al. 2005  Cancer Res  65:5417-5427; Papanicolaou, G. A., et al. 2003  Blood  102:2498-2505 (disclosing selectively in vitro-expanded antigen-specific peripheral blood leukocytes employing artificial antigen-presenting cells (AAPCs) or pulsed dendritic cells). The cells (e.g., T cells) can be autologous, non-autologous (e.g., allogeneic), or derived in vitro from engineered progenitor or stem cells. 
     In certain embodiments, the cells of are cells of the myeloid lineage. In certain embodiments, the cells of the myeloid lineage comprise, without limitation, monocytes, macrophages, basophils, neutrophils, eosinophils, mast cell, erythrocyte, and thrombocytes. 
     The presently disclosed cells are capable of modulating the tumor microenvironment. Tumors have a microenvironment that suppresses the host immune response using any of a series of mechanisms by malignant cells to protect themselves from immune surveillance, recognition and elimination. Immune suppressive factors include, but are not limited to infiltrating regulatory CD4 +  T cells (Tregs), myeloid derived suppressor cells (MDSCs), tumor associated macrophages (TAMs), immune suppressive cytokines including TGF-β, and expression of ligands targeted to immune suppressive receptors expressed by activated T cells (CTLA-4 and PD-1). These mechanisms of immune suppression play a role in the maintenance of tolerance and suppressing inappropriate immune responses, however within the tumor microenvironment these mechanisms prevent an effective anti-tumor immune response. Collectively these immune suppressive factors can induce either marked anergy or apoptosis of adoptively transferred modified T cells (e.g., CART cells) upon encounter with targeted tumor cells. 
     In certain embodiments, the presently disclosed cells have increased cell persistence. In certain embodiments, the presently disclosed cells have decreased apoptosis and/or anergy. 
     The unpurified source of CTLs may be any known in the art, such as the bone marrow, fetal, neonate or adult or other hematopoietic cell source, e.g., fetal liver, peripheral blood or umbilical cord blood. Various techniques can be employed to separate the cells. For instance, negative selection methods can remove non-CTLs initially. Monoclonal antibodies (mAbs) are particularly useful for identifying markers associated with particular cell lineages and/or stages of differentiation for both positive and negative selections. 
     A large proportion of terminally differentiated cells can be initially removed by a relatively crude separation. For example, magnetic bead separations can be used initially to remove large numbers of irrelevant cells. In certain embodiments, at least about 80%, usually at least 70% of the total hematopoietic cells will be removed prior to cell isolation. 
     Procedures for separation include, but are not limited to, density gradient centrifugation; resetting; coupling to particles that modify cell density; magnetic separation with antibody-coated magnetic beads; affinity chromatography; cytotoxic agents joined to or used in conjunction with a mAb, including, but not limited to, complement and cytotoxins; and panning with antibody attached to a solid matrix, e.g. plate, chip, elutriation or any other convenient technique. 
     Techniques for separation and analysis include, but are not limited to, flow cytometry, which can have varying degrees of sophistication, e.g., a plurality of color channels, low angle and obtuse light scattering detecting channels, impedance channels. 
     The cells can be distinguished from dead cells, by employing dyes associated with dead cells such as propidium iodide (PI). In certain embodiments, the cells are collected in a medium comprising 2% fetal calf serum (FCS) or 0.2% bovine serum albumin (BSA) or any other suitable, e.g., sterile, isotonic medium. 
     5. Nucleic Acid Compositions and Vectors 
     The present discloses subject matter provides nucleic acid compositions comprising a first polynucleotide encoding a membrane-bound polypeptide disclosed herein (e.g., disclosed in Section 1) and a second polynucleotide encoding a solute polypeptide disclosed herein (e.g., disclosed in Section 2). Also provided are cells comprising such nucleic acid compositions. 
     In certain embodiments, the membrane-bound polypeptide encoded by the first polynucleotide comprises: i) a transmembrane domain, ii) an intracellular domain, and iii) an extracellular domain that comprises a first dimerization domain and a blocking spacer, and the soluble polypeptide encoded by the second polynucleotide comprises i) a second dimerization domain, and ii) an antigen binding domain that binds to an antigen. In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain, and the blocking spacer prevents the dimerization of the membrane-bound polypeptide with the soluble polypeptide when the membrane-bound polypeptide and the soluble polypeptide are not expressed from the same cell. 
     In certain embodiments, the membrane-bound polypeptide encoded by the first polynucleotide comprises: i) a transmembrane domain, ii) an intracellular domain, and iii) an extracellular domain that comprises a first dimerization domain and a second dimerization domain that is capable of dimerizing with the first dimerization domain, and the soluble polypeptide encoded by the second polynucleotide comprises i) a third dimerization domain that is capable of dimerizing with the first dimerization domain, and ii) an antigen binding domain that binds to an antigen. In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain. 
     In certain embodiments, the membrane-bound polypeptide encoded by the first polynucleotide comprises a transmembrane domain and an extracellular domain comprising a first dimerization domain, and the soluble polypeptide encoded by the second polynucleotide comprising a second dimerization domain that is capable of dimerizing with the first dimerization domain, and a cytokine or chemokine. In certain embodiments, each of the first dimerization domain and the second dimerization domain comprises a leucine zipper domain. 
     In certain embodiments, the first polynucleotide is comprised in a first vector, and the second polynucleotide is comprised in a second vector. In certain embodiments, the first vector and/or the second vector is a viral vector or a transposon-based vector. In certain embodiments, the viral vector is a retroviral vector. In certain embodiments, the retroviral vector is a lentiviral vector. The first vector can the same as the second vector, or different from the second vector. In certain embodiments, the first vector is the same as the second vector, for example, the vector backbone for the first and the second vectors can be the same, while the polypeptide or protein encoded/expressed by the first and second vectors can be different. 
     Genetic modification of a cell (e.g., a T cell) can be accomplished by transducing a substantially homogeneous cell composition with a recombinant DNA construct. In certain embodiments, a retroviral vector is employed for the introduction of the DNA construct into the cell. For example, a polynucleotide encoding any polypeptide or system disclosed herein can be cloned into a retroviral vector and expression can be driven from its endogenous promoter, from the retroviral long terminal repeat, or from a promoter specific for a target cell type of interest. In certain embodiments, the retroviral vector is a gamma-retroviral vector. In certain embodiments, the retroviral vector is a lentiviral vector. Non-viral vectors may be used as well. 
     For initial genetic modification of a cell to include a polypeptide and/or a system disclosed herein, a retroviral vector is generally employed for transduction, however any other suitable viral vector or non-viral delivery system can be used. The polypeptides and/or the system can be constructed in a single, multicistronic expression cassette, in multiple expression cassettes of a single vector, or in multiple vectors. Examples of elements that create polycistronic expression cassette include, but is not limited to, various viral and non-viral Internal Ribosome Entry Sites (IRES, e.g., FGF-1 IRES, FGF-2 IRES, VEGF IRES, IGF-II IRES, NF-κB IRES, RUNX1 IRES, p53 IRES, hepatitis A IRES, hepatitis C IRES, pestivirus IRES, aphthovirus IRES, picornavirus IRES, poliovirus IRES and encephalomyocarditis virus IRES) and cleavable linkers (e.g., 2A peptides, e.g., P2A, T2A, E2A and F2A peptides). Combinations of retroviral vector and an appropriate packaging line are also suitable, where the capsid proteins will be functional for infecting human cells. Various amphotropic virus-producing cell lines are known, including, but not limited to, PA12 (Miller, et al. (1985)  Mol. Cell. Biol.  5:431-437); PA317 (Miller, et al. (1986)  Mol. Cell. Biol.  6:2895-2902); and CRIP (Danos, et al. (1988)  Proc. Natl. Acad. Sci. USA  85:6460-6464). Non-amphotropic particles are suitable too, e.g., particles pseudotyped with VSVG, RD114 or GALV envelope and any other known in the art. 
     Possible methods of transduction also include direct co-culture of the cells with producer cells, e.g., by the method of Bregni, et al. (1992)  Blood  80:1418-1422, or culturing with viral supernatant alone or concentrated vector stocks with or without appropriate growth factors and polycations, e.g., by the method of Xu, et al. (1994)  Exp. Hemat.  22:223-230; and Hughes, et al. (1992)  J. Clin. Invest.  89:1817. 
     Other transducing viral vectors can be used to modify a cell. In certain embodiments, the chosen vector exhibits a high efficiency of infection, stable integration into the host cell genome, and durable expression of the recombinant gene product(s) (see, e.g., Cayouette et al., Human Gene Therapy 8:423-430, 1997; Kido et al., Current Eye Research 15:833-844, 1996; Bloomer et al., Journal of Virology 71:6641-6649, 1997; Naldini et al., Science 272:263-267, 1996; and Miyoshi et al., Proc. Natl. Acad. Sci. U.S.A. 94:10319, 1997). Other viral vectors that can be used include, for example, adenoviral, lentiviral, and adeno-associated viral vectors, vaccinia virus, a bovine papilloma virus, or a herpes virus, such as Epstein-Barr Virus (also see, for example, the vectors of Miller, Human Gene Therapy 15-14, 1990; Friedman, Science 244:1275-1281, 1989; Eglitis et al., BioTechniques 6:608-614, 1988; Tolstoshev et al., Current Opinion in Biotechnology 1:55-61, 1990; Sharp, The Lancet 337:1277-1278, 1991; Cornetta et al., Nucleic Acid Research and Molecular Biology 36:311-322, 1987; Anderson, Science 226:401-409, 1984; Moen, Blood Cells 17:407-416, 1991; Miller et al., Biotechnology 7:980-990, 1989; LeGal La Salle et al., Science 259:988-990, 1993; and Johnson, Chest 107:77S-83S, 1995). Retroviral vectors are particularly well developed and have been used in clinical settings (Rosenberg et al., N. Engl. J. Med 323:370, 1990; Anderson et al., U.S. Pat. No. 5,399,346). 
     Non-viral approaches can also be employed for genetic modification of a cell. For example, a nucleic acid molecule can be introduced into a cell by administering the nucleic acid in the presence of lipofection (Feigner et al., Proc. Natl. Acad. Sci. U.S.A. 84:7413, 1987; Ono et al., Neuroscience Letters 17:259, 1990; Brigham et al., Am. J. Med. Sci. 298:278, 1989; Staubinger et al., Methods in Enzymology 101:512, 1983), asialoorosomucoid-polylysine conjugation (Wu et al., Journal of Biological Chemistry 263:14621, 1988; Wu et al., Journal of Biological Chemistry 264:16985, 1989), or by micro-injection under surgical conditions (Wolff et al., Science 247:1465, 1990). Other non-viral means for gene transfer include transfection in vitro using calcium phosphate, DEAE dextran, electroporation, and protoplast fusion. Liposomes can also be potentially beneficial for delivery of DNA into a cell. Transplantation of normal genes into the affected tissues of a subject can also be accomplished by transferring a normal nucleic acid into a cultivatable cell type ex vivo (e.g., an autologous or heterologous primary cell or progeny thereof), after which the cell (or its descendants) are injected into a targeted tissue or are injected systemically. Recombinant receptors can also be derived or obtained using transposases or targeted nucleases (e.g. Zinc finger nucleases, meganucleases, or TALENs nucleases, CRISPR). Transient expression may be obtained by RNA electroporation. In certain embodiments, recombinant receptors can be introduced by a transposon-based vector. In certain embodiments, the transposon-based vector comprises a transposon (a.k.a. a transposable element). In certain embodiments, the transposon can be recognized by a transposase. In certain embodiments, the transposase is a Sleeping Beauty transposase. 
     The resulting cells can be grown under conditions similar to those for unmodified cells, whereby the modified cells can be expanded and used for a variety of purposes. 
     6. Polypeptides and Analogs 
     Also included in the presently disclosed subject matter are CD28, CD8, CD80, 4-1BBL, and CD3ζ polypeptides, the membrane-bound polypeptide disclosed herein, and the soluble polypeptide disclosed herein or fragments thereof that are modified in ways that enhance their therapeutic efficacy when expressed in a cell. The presently disclosed subject matter provides methods for optimizing an amino acid sequence or nucleic acid sequence by producing an alteration in the sequence. Such alterations may include certain mutations, deletions, insertions, or post-translational modifications. The presently disclosed subject matter further includes analogs of any naturally-occurring polypeptide disclosed herein (including, but not limited to, CD8, CD28, CD80, 4-1BBL, and CD3ζ). Analogs can differ from a naturally-occurring polypeptide disclosed herein by amino acid sequence differences, by post-translational modifications, or by both. Analogs can exhibit at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or at least about 100% homologous to all or part of a naturally-occurring amino, acid sequence of the presently disclosed subject matter. The length of sequence comparison is at least 5, 10, 15 or 20 amino acid residues, e.g., at least 25, 50, or 75 amino acid residues, or more than 100 amino acid residues. Again, in an exemplary approach to determining the degree of identity, a BLAST program may be used, with a probability score between e −3  and e −100  indicating a closely related sequence. Modifications include in vivo and in vitro chemical derivatization of polypeptides, e.g., acetylation, carboxylation, phosphorylation, or glycosylation; such modifications may occur during polypeptide synthesis or processing or following treatment with isolated modifying enzymes. Analogs can also differ from the naturally-occurring polypeptides by alterations in primary sequence. These include genetic variants, both natural and induced (for example, resulting from random mutagenesis by irradiation or exposure to ethanemethylsulfate or by site-specific mutagenesis as described in Sambrook, Fritsch and Maniatis, Molecular Cloning: A Laboratory Manual (2d ed.), CSH Press, 1989, or Ausubel et al., supra). Also included are cyclized peptides, molecules, and analogs which contain residues other than L-amino acids, e.g., D-amino acids or non-naturally occurring or synthetic amino acids, e.g., β or γ amino acids. 
     In addition to full-length polypeptides, the presently disclosed subject matter also provides fragments of any one of the polypeptides or peptide domains disclosed herein. As used herein, the term “a fragment” means at least 5, 10, 13, or 15 amino acids. In certain embodiments, a fragment comprises at least 20 contiguous amino acids, at least 30 contiguous amino acids, or at least 50 contiguous amino acids. In certain embodiments, a fragment comprises at least 60 to 80, 100, 200, 300 or more contiguous amino acids. Fragments can be generated by methods known to those skilled in the art or may result from normal protein processing (e.g., removal of amino acids from the nascent polypeptide that are not required for biological activity or removal of amino acids by alternative mRNA splicing or alternative protein processing events). 
     Non-protein analogs have a chemical structure designed to mimic the functional activity of a protein/peptide disclosed herein. Such analogs may exceed the physiological activity of the original polypeptide. Methods of analog design are well known in the art, and synthesis of analogs can be carried out according to such methods by modifying the chemical structures such that the resultant analogs increase the anti-neoplastic activity of the original polypeptide when expressed in a cell. These chemical modifications include, but are not limited to, substituting alternative R groups and varying the degree of saturation at specific carbon atoms of a reference polypeptide. In certain embodiments, the protein analogs are relatively resistant to in vivo degradation, resulting in a more prolonged therapeutic effect upon administration. Assays for measuring functional activity include, but are not limited to, those described in the Examples below. 
     7. Administration 
     Compositions comprising the presently disclosed cells can be provided systemically or directly to a subject for inducing and/or enhancing an immune response to an antigen and/or treating and/or preventing a neoplasia, pathogen infection, or infectious disease. In certain embodiments, the presently disclosed cells or compositions comprising thereof are directly injected into an organ of interest (e.g., an organ affected by a neoplasia). Alternatively, the presently disclosed cells or compositions comprising thereof are provided indirectly to the organ of interest, for example, by administration into the circulatory system (e.g., the tumor vasculature). Expansion and differentiation agents can be provided prior to, during or after administration of the cells or compositions to increase production of T cells, NK cells, or CTL cells in vitro or in vivo. 
     The presently disclosed cells can be administered in any physiologically acceptable vehicle, normally intravascularly, although they may also be introduced into bone or other convenient site where the cells may find an appropriate site for regeneration and differentiation (e.g., thymus). Usually, at least about 1×10 5  cells will be administered, eventually reaching about 1×10 10  or more. The presently disclosed cells can comprise a purified population of cells. Those skilled in the art can readily determine the percentage of the presently disclosed cells in a population using various well-known methods, such as fluorescence activated cell sorting (FACS). Suitable ranges of purity in populations comprising the presently disclosed cells are about 50% to about 55%, about 5% to about 60%, and about 65% to about 70%. In certain embodiments, the purity is about 70% to about 75%, about 75% to about 80%, or about 80% to about 85%. In certain embodiments, the purity is about 85% to about 90%, about 90% to about 95%, and about 95% to about 100%. Dosages can be readily adjusted by those skilled in the art (e.g., a decrease in purity may require an increase in dosage). The cells can be introduced by injection, catheter, or the like. 
     The presently disclosed compositions can be pharmaceutical compositions comprising the presently disclosed cells and a pharmaceutically acceptable carrier. Administration can be autologous or heterologous. For example, cells can be obtained from one subject, and administered to the same subject or a different, compatible subject. Peripheral blood derived cells or their progeny (e.g., in vivo, ex vivo or in vitro derived) can be administered via localized injection, including catheter administration, systemic injection, localized injection, intravenous injection, or parenteral administration. When administering a therapeutic composition of the presently disclosed subject matter (e.g., a pharmaceutical composition comprising a presently disclosed cell), it can be formulated in a unit dosage injectable form (solution, suspension, emulsion). 
     8. Formulations 
     Compositions comprising the presently disclosed cells can be conveniently provided as sterile liquid preparations, e.g., isotonic aqueous solutions, suspensions, emulsions, dispersions, or viscous compositions, which may be buffered to a selected pH. Liquid preparations are normally easier to prepare than gels, other viscous compositions, and solid compositions. Additionally, liquid compositions are somewhat more convenient to administer, especially by injection. Viscous compositions, on the other hand, can be formulated within the appropriate viscosity range to provide longer contact periods with specific tissues. Liquid or viscous compositions can comprise carriers, which can be a solvent or dispersing medium containing, for example, water, saline, phosphate buffered saline, polyol (for example, glycerol, propylene glycol, liquid polyethylene glycol, and the like) and suitable mixtures thereof. 
     Sterile injectable solutions can be prepared by incorporating the cells in the required amount of the appropriate solvent with various amounts of the other ingredients, as desired. Such compositions may be in admixture with a suitable carrier, diluent, or excipient such as sterile water, physiological saline, glucose, dextrose, or the like. The compositions can also be lyophilized. The compositions can contain auxiliary substances such as wetting, dispersing, or emulsifying agents (e.g., methylcellulose), pH buffering agents, gelling or viscosity enhancing additives, preservatives, flavoring agents, colors, and the like, depending upon the route of administration and the preparation desired. Standard texts, such as “REMINGTON&#39;S PHARMACEUTICAL SCIENCE”, 17th edition, 1985, incorporated herein by reference, may be consulted to prepare suitable preparations, without undue experimentation. 
     Various additives which enhance the stability and sterility of the compositions, including antimicrobial preservatives, antioxidants, chelating agents, and buffers, can be added. Prevention of the action of microorganisms can be ensured by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, and the like. Prolonged absorption of the injectable pharmaceutical form can be brought about by the use of agents delaying absorption, for example, aluminum monostearate and gelatin. According to the presently disclosed subject matter, however, any vehicle, diluent, or additive used would have to be compatible with the cells or their progenitors. 
     The compositions can be isotonic, i.e., they can have the same osmotic pressure as blood and lacrimal fluid. The desired isotonicity of the compositions may be accomplished using sodium chloride, or other pharmaceutically acceptable agents such as dextrose, boric acid, sodium tartrate, propylene glycol or other inorganic or organic solutes. Sodium chloride can be particularly for buffers containing sodium ions. 
     Viscosity of the compositions, if desired, can be maintained at the selected level using a pharmaceutically acceptable thickening agent. For example, methylcellulose is readily and economically available and is easy to work with. Other suitable thickening agents include, for example, xanthan gum, carboxymethyl cellulose, hydroxypropyl cellulose, carbomer, and the like. The concentration of the thickener can depend upon the agent selected. The important point is to use an amount that will achieve the selected viscosity. Obviously, the choice of suitable carriers and other additives will depend on the exact route of administration and the nature of the particular dosage form, e.g., liquid dosage form (e.g., whether the composition is to be formulated into a solution, a suspension, gel or another liquid form, such as a time release form or liquid-filled form). 
     The quantity of cells to be administered will vary for the subject being treated. In a one embodiment, between about 10 4  and about 10 10 , between about 10 5  and about 10 9 , or between about 10 6  and about 10 8  of the presently disclosed cells are administered to a human subject. More effective cells may be administered in even smaller numbers. In certain embodiments, at least about 1×10 8 , about 2×10 8 , about 3×10 8 , about 4×10 8 , or about 5×10 8  of the presently disclosed cells are administered to a human subject. The precise determination of what would be considered an effective dose may be based on factors individual to each subject, including their size, age, sex, weight, and condition of the particular subject. Dosages can be readily ascertained by those skilled in the art from this disclosure and the knowledge in the art. 
     The skilled artisan can readily determine the amount of cells and optional additives, vehicles, and/or carrier in compositions and to be administered in methods. Typically, any additives (in addition to the active cell(s) and/or agent(s)) are present in an amount of 0.001 to 50% (weight) solution in phosphate buffered saline, and the active ingredient is present in the order of micrograms to milligrams, such as about 0.0001 to about 5 wt %, about 0.0001 to about 1 wt %, about 0.0001 to about 0.05 wt % or about 0.001 to about 20 wt %, about 0.01 to about 10 wt %, or about 0.05 to about 5 wt %. For any composition to be administered to an animal or human, the followings can be determined: toxicity such as by determining the lethal dose (LD) and LD50 in a suitable animal model e.g., rodent such as mouse; the dosage of the composition(s), concentration of components therein and timing of administering the composition(s), which elicit a suitable response. Such determinations do not require undue experimentation from the knowledge of the skilled artisan, this disclosure and the documents cited herein. And, the time for sequential administrations can be ascertained without undue experimentation. 
     9. Methods of Treatment 
     The presently disclosed subject matter provides methods for inducing and/or increasing an immune response in a subject in need thereof. In certain embodiments, the method comprises administering to a subject an effective amount of the cells disclosed herein or a pharmaceutical composition comprising such cells. The presently disclosed cells and compositions comprising thereof can be used for treating and/or preventing neoplasia in a subject. The presently disclosed cells and compositions comprising thereof can be used for prolonging the survival of a subject suffering from a neoplasm. The presently disclosed cells and compositions comprising thereof can also be used for treating and/or preventing a pathogen infection or other infectious disease in a subject, such as an immunocompromised human subject. Such methods comprise administering an amount effective the presently disclosed cells or a composition (e.g., a pharmaceutical composition) comprising such cells to achieve the desired effect, be it palliation of an existing condition or prevention of recurrence. For treatment, the amount administered is an amount effective in producing the desired effect. An effective amount can be provided in one or a series of administrations. An effective amount can be provided in a bolus or by continuous perfusion. 
     An “effective amount” (or, “therapeutically effective amount”) is an amount sufficient to effect a beneficial or desired clinical result upon treatment. An effective amount can be administered to a subject in one or more doses. In terms of treatment, an effective amount is an amount that is sufficient to palliate, ameliorate, stabilize, reverse or slow the progression of the disease, or otherwise reduce the pathological consequences of the disease. The effective amount is generally determined by the physician on a case-by-case basis and is within the skill of one in the art. Several factors are typically taken into account when determining an appropriate dosage to achieve an effective amount. These factors include age, sex and weight of the subject, the condition being treated, the severity of the condition and the form and effective concentration of the cells administered. 
     For adoptive immunotherapy using antigen-specific T cells, cell doses in the range of about 10 6 -10 10  (e.g., about 10 9 ) are typically infused. Upon administration of the presently disclosed cells into the host and subsequent differentiation, T cells are induced that are specifically directed against the specific antigen. The modified cells can be administered by any method known in the art including, but not limited to, intravenous, subcutaneous, intranodal, intratumoral, intrathecal, intrapleural, intraperitoneal and directly to the thymus. 
     The presently disclosed subject matter provides methods for treating and/or preventing a neoplasia in a subject. The method can comprise administering an effective amount of the presently disclosed cells or a composition (e.g., a pharmaceutical composition) comprising such cells to a subject having a neoplasia. 
     Non-limiting examples of neoplasia include blood cancers (e.g. leukemias, lymphomas, and myelomas), ovarian cancer, breast cancer, bladder cancer, brain cancer, colon cancer, intestinal cancer, liver cancer, lung cancer, pancreatic cancer, prostate cancer, skin cancer, stomach cancer, glioblastoma, throat cancer, melanoma, neuroblastoma, adenocarcinoma, glioma, soft tissue sarcoma, and various carcinomas (including prostate and small cell lung cancer). Other carcinomas that may be treated with cells comprising the systems disclosed herein include any known in the field of oncology, including, but not limited to, astrocytoma, fibrosarcoma, myxosarcoma, liposarcoma, oligodendroglioma, ependymoma, medulloblastoma, primitive neural ectodermal tumor (PNET), chondrosarcoma, osteogenic sarcoma, pancreatic ductal adenocarcinoma, small and large cell lung adenocarcinomas, chordoma, angiosarcoma, endotheliosarcoma, squamous cell carcinoma, bronchoalveolarcarcinoma, epithelial adenocarcinoma, and liver metastases thereof, lymphangiosarcoma, lymphangioendotheliosarcoma, hepatoma, cholangiocarcinoma, synovioma, mesothelioma, Ewing&#39;s tumor, rhabdomyosarcoma, colon carcinoma, basal cell carcinoma, sweat gland carcinoma, papillary carcinoma, sebaceous gland carcinoma, papillary adenocarcinoma, cystadenocarcinoma, medullary carcinoma, bronchogenic carcinoma, renal cell carcinoma, bile duct carcinoma, choriocarcinoma, seminoma, embryonal carcinoma, Wilms&#39; tumor, testicular tumor, medulloblastoma, crani opharyngioma, ependymoma, pinealoma, hemangioblastoma, acoustic neuroma, oligodendroglioma, meningioma, neuroblastoma, retinoblastoma, leukemia, multiple myeloma, Waldenstrom&#39;s macroglobulinemia, and heavy chain disease, breast tumors such as ductal and lobular adenocarcinoma, squamous and adenocarcinomas of the uterine cervix, uterine and ovarian epithelial carcinomas, prostatic adenocarcinomas, transitional squamous cell carcinoma of the bladder, B and T cell lymphomas (nodular and diffuse) plasmacytoma, acute and chronic leukemias, malignant melanoma, soft tissue sarcomas and leiomyosarcomas. In certain embodiments, the neoplasia is selected from the group consisting of blood cancers (e.g. leukemias, lymphomas, and myelomas), ovarian cancer, prostate cancer, breast cancer, bladder cancer, brain cancer, colon cancer, intestinal cancer, liver cancer, lung cancer, pancreatic cancer, prostate cancer, skin cancer, stomach cancer, glioblastoma, and throat cancer. In certain embodiments, the presently disclosed cells and compositions comprising thereof can be used for treating and/or preventing blood cancers (e.g., leukemias, lymphomas, and myelomas) or ovarian cancer, which are not amenable to conventional therapeutic interventions. 
     The subjects can have an advanced form of disease, in which case the treatment objective can include mitigation or reversal of disease progression, and/or amelioration of side effects. The subjects can have a history of the condition, for which they have already been treated, in which case the therapeutic objective will typically include a decrease or delay in the risk of recurrence. 
     Suitable human subjects for therapy typically comprise two treatment groups that can be distinguished by clinical criteria. Subjects with “advanced disease” or “high tumor burden” are those who bear a clinically measurable tumor. A clinically measurable tumor is one that can be detected on the basis of tumor mass (e.g., by palpation, CAT scan, sonogram, mammogram or X-ray; positive biochemical or histopathologic markers on their own are insufficient to identify this population). A pharmaceutical composition is administered to these subjects to elicit an anti-tumor response, with the objective of palliating their condition. Ideally, reduction in tumor mass occurs as a result, but any clinical improvement constitutes a benefit. Clinical improvement includes decreased risk or rate of progression or reduction in pathological consequences of the tumor. 
     A second group of suitable subjects is known in the art as the “adjuvant group.” These are individuals who have had a history of neoplasia, but have been responsive to another mode of therapy. The prior therapy can have included, but is not restricted to, surgical resection, radiotherapy, and traditional chemotherapy. As a result, these individuals have no clinically measurable tumor. However, they are suspected of being at risk for progression of the disease, either near the original tumor site, or by metastases. This group can be further subdivided into high-risk and low-risk individuals. The subdivision is made on the basis of features observed before or after the initial treatment. These features are known in the clinical arts, and are suitably defined for each different neoplasia. Features typical of high-risk subgroups are those in which the tumor has invaded neighboring tissues, or who show involvement of lymph nodes. 
     Another group have a genetic predisposition to neoplasia but have not yet evidenced clinical signs of neoplasia. For instance, women testing positive for a genetic mutation associated with breast cancer, but still of childbearing age, can wish to receive one or more of the cells described herein in treatment prophylactically to prevent the occurrence of neoplasia until it is suitable to perform preventive surgery. 
     Additionally, the presently disclosed subject matter provides methods for treating and/or preventing a pathogen infection (e.g., viral infection, bacterial infection, fungal infection, parasite infection, or protozoal infection) in a subject, e.g., in an immunocompromised subject. The method can comprise administering an effective amount of the presently disclosed cells or a composition (e.g., a pharmaceutical composition) comprising such cells to a subject having a pathogen infection. Exemplary viral infections susceptible to treatment include, but are not limited to, Cytomegalovirus (CMV), Epstein Barr Virus (EBV), Human Immunodeficiency Virus (HIV), and influenza virus infections. 
     The presently disclosed subject matter further provides methods for increasing an immune activity of an immunoresponsive cell. In certain embodiments, the method comprises introducing to the immunoresponsive cell a system disclosed herein to the immunoresponsive cell. 
     The presently disclosed subject matter provides methods for activating an antigen presenting cell (APC) in a subject. In certain embodiments, the method comprises administering to the subject an effective amount of the cells or a composition (e.g., a pharmaceutical composition) comprising such cells. 
     The presently disclosed subject matter provides methods for conditioning a subject for bone marrow transplant. In certain embodiments, the method comprises administering to the subject an effective amount of the cells or a composition (e.g., a pharmaceutical composition) comprising such cells. 
     Further modification can be introduced to the presently disclosed cells (e.g., T cells) to avert or minimize the risks of immunological complications (known as “malignant T-cell transformation”), e.g., graft versus-host disease (GvHD), or when healthy tissues express the same target antigens as the tumor cells, leading to outcomes similar to GvHD. A potential solution to this problem is engineering a suicide gene into the presently disclosed cells. Suitable suicide genes include, but are not limited to, Herpes simplex virus thymidine kinase (hsv-tk), and inducible Caspase 9 Suicide gene (iCasp-9). In certain embodiments, the cells include a truncated human epidermal growth factor receptor (EGFRt) polypeptide. The EGFRt polypeptide can enable T cell elimination by administering anti-EGFR monoclonal antibody (e.g., cetuximab). EGFRt can be covalently joined to the upstream of any polypeptide disclosed herein. The suicide gene can be included within the vector comprising nucleic acids encoding any polypeptide disclosed herein. In this way, administration of a prodrug designed to activate the suicide gene (e.g., a prodrug (e.g., AP1903 that can activate iCasp-9) during malignant T-cell transformation (e.g., GVHD) triggers apoptosis in the suicide gene-activated T cells comprising any polypeptide or system disclosed herein. The incorporation of a suicide gene or EDFRt into the presently disclosed polypeptide or system gives an added level of safety with the ability to eliminate the majority of the engineered T cells within a very short time period. A presently disclosed cell (e.g., a T cell) incorporated with a suicide gene can be pre-emptively eliminated at a given timepoint post engineered T cell infusion, or eradicated at the earliest signs of toxicity. 
     EXAMPLES 
     The practice of the present disclosure employs, unless otherwise indicated, conventional techniques of molecular biology (including recombinant techniques), microbiology, cell biology, biochemistry and immunology, which are well within the purview of the skilled artisan. Such techniques are explained fully in the literature, such as, “Molecular Cloning: A Laboratory Manual”, second edition (Sambrook, 1989); “Oligonucleotide Synthesis” (Gait, 1984); “Animal Cell Culture” (Freshney, 1987); “Methods in Enzymology” “Handbook of Experimental Immunology” (Weir, 1996); “Gene Transfer Vectors for Mammalian Cells” (Miller and Calos, 1987); “Current Protocols in Molecular Biology” (Ausubel, 1987); “PCR: The Polymerase Chain Reaction”, (Mullis, 1994); “Current Protocols in Immunology” (Coligan, 1991). These techniques are applicable to the production of the polynucleotides and polypeptides of the invention, and, as such, may be considered in making and practicing the invention. Particularly useful techniques for particular embodiments will be discussed in the sections that follow. 
     The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the systems and methods of the present disclosure, and are not intended to limit the scope of what the inventors regard as their invention. 
     Example 1—Chimeric Antigen Receptors with scFv Leucine Zipper Sorting Affinity Tags 
     A binary, leucine zipper-based, affinity tag system was developed to allow selective sorting of cells with simultaneous co-transduction with two viral vectors to allow transfer of larger amounts of genetic information without exceeding packaging limits of the viruses. In this system, one viral vector encoded a leucine zipper (e.g., RR12EE345L) with a linked affinity tag (e.g. FLAG, streptag, myc, etc.) ( FIG. 1 ). The second viral vector encoded a membrane-bound leucine zipper (e.g., EE12RR345L) with high predilection to form a heterodimer with the RR12EE345L-affinity tag leucine zipper. When co-transduced into the same target cell, surface capture of the RR12EE345L-affinity tag by the membrane-bound EE12RR345L leucine zipper occurred, allowing surface detection of the affinity tag by flow cytometry and immuno-magnetic selection using magnetic beads conjugated to antibodies specific for the affinity tag. 
     A binary CAR system was developed in which a universal adaptor CAR can pair extracellularly with scFv molecules to generate functional CAR molecules capable of targeting tumor cells by genetically modified T cells. The above leucine zipper-based sorting strategy was used to engineer T cells with two vectors. Vector 1 encoded multiple scFv-affinity tag-leucine zipper (e.g., RR12EE345L) specific for multiple tumor antigens to limit tumor immune evasion by down-modulation of tumor associated antigens. Vector 2 encoded a leucine zipper-based CAR (sometime also referred to as leucine zipper receptor-based CAR, “ZipR-CAR”) (e.g. EE12RR345L:CD28zeta), and other molecules including, but are not limited to: degenerate leucine-zipper based CCR (described below), cytokines, and suicide genes ( FIGS. 1 and 2 ). As shown in  FIG. 1 , blocked leucine zipper CAR (“ZipR-CAR”) construct allows sorting of cells transduced with scFv affinity-tagged leucine zippers and limits surface expression of scFv to dual transduced cells. Un-blocked leucine zipper CAR allows extracellular provision of scFvs (injected into host or delivered from other cells). Leucine zipper CAR vector can encode multiple genes including cytokines, suicide genes, costimulatory molecules and more. ScFv vector can encode at least 4 antigen specificities. Certain ZipR-CARs appear to be intrinsically blocked and do not require expression of the additional linked blocking leucine zipper (right panel) in order to avoid extracellular paring pathway (“painting”). See e.g.,  FIGS. 3 and 6 . As shown in  FIG. 3 , painting ZipR-CAR is able to capture soluble tagged heterodimerizing leucine zipper from media. Non-painting leucine zippers can only obtain the tagged heterodimerizing leucine zipper during production inside the T cell. Other suitable spacers include a CD28 hinge, a non-dimerizing CD8 and IgG1. Other suitable tags include Strep-tag, HA-tag, His-tag, etc. As shown in  FIG. 6 , CD19/CD20 scFv vector promoted killing of CD19 or CD20 +  cells by EE-CARs, and Myc-tag-only spacer led to target killing effects. Mouse T cells expressing dual CD19/CD20 scFv-FLAG-RR12EE345L/EE-CAR complex were able to specifically kill target cells expressing either CD19 or CD20 (OR gate). ZipR-CAR lacking spacers promoted enhanced target killing compared to larger CD8 extracellular domain hinge spacer. 
     The leucine zipper-based CAR can include a “self-blocking” feature to allow selective sorting of T cells co-transduced with vector 1 and 2. Under certain circumstances, ZipR-CAR was self-blocking without addition of a linked heterodimerizing zipper (see  FIGS. 1, 3, and 5 ). For example, as shown in  FIG. 5 , despite same staining intensity of FLAG tag in the BFP+ Thy1.1+ population, the FLAG tag did not bind to the IgG1 spacer ZipR-CAR via extracellular secretion (see middle left panel of  FIG. 5 ). There were fewer absolute FLAG+ cells with IgG1 spacer due to absence of “painted” cell population (see bottom panel of  FIG. 5 ). When co-integrated into the same T cell, vector 1 and 2 led to the expression of affinity tagged scFvs bound to the ZipR-CAR, which caused killing of targets expressing antigens bound by the scFvs (see  FIGS. 4, 6, 7, and 9 ). As shown in  FIG. 4 , expressions of various tags were detected and where CD19 scFv were captured; and the T cells were able to kill CD19 +  targets. The self-blocking feature permitted selective expression of a genetically defined set of Leucine zipper-scFvs in a single T cell, which could not appreciably bind exogenously secreted or infused Zipper-scFvs. Additionally, the self-blocking feature allowed sorting of T cells that had integrated both the scFv vector and the ZipR-CAR vector. As shown in  FIG. 7 , CD19/CD20 scFv vector promoted killing of CD19 or CD20 +  cells by EE-CARs, and Myc-tag-only spacer promoted targeted killing of larger CD19 target. As shown in  FIG. 9 , CD19/CD20/IL-3 scFv vector promoted killing of cells expressing CD19, CD20, or CD123/CD131(IL-3R) by EE-CARs. In particular, CD19/CD20 scFv+ZipR-CAR T cells were able to kill CD19+ and CD20+ targets (targeting mouse B cells and B cell leukemia). See  FIG. 9 . IL-3 zipperkine+ZipR-CAR T cells were able to kill IL-3R+ targets (targeting mouse early myeloid cells and B cell and acute myeloid leukemia). See  FIG. 9 . No-spacer and IgG1 ZipR-CAR promoted equivalent lysis versus CD19, CD20, and IL3R +  targets. See  FIG. 9 . 
     A new design of the membrane-bound leucine zipper was developed that can inhibit the binding of soluble tagged leucine zippers secreted by other cells, but still allows binding of internally generated tagged zippers, without the self-blocking feature described in Example 1. Such a membrane-bound polypeptide comprised a very small extracellular domain, e.g., a spacer/hinge domain comprising no more than 20 amino acid residues, which precluded antibody epitopes like Thy1.1 or EGFRt. For example, a membrane-bound leucine zipper polypeptide comprising a CD8 spacer demonstrated binding of soluble scFv leucine zippers expressed both from the same cell that expressed the membrane-bound polypeptide and from other cells. However, a membrane-bound leucine zipper polypeptide comprising a truncated CD28 9 amino acid spacer or an IgG1 hinge only bound soluble scFv leucine zippers expressed in the same cell with the membrane-bound polypeptide. 
       FIGS. 25A-25C  further demonstrate that tetracycline-inducible ZipR-CAR system enabled drug-induced ZipR-CAR expression and MACS sorting for double-transduced cells. Primary T cells dual transduced with two vectors: (1) self-inactivating retrovirus containing tetracycline response element (tre3g) driving expression of CD19 and CD20 scFvs tagged with FLAG and fused to RR12EE345L leucine zipper and (2) retrovirus encoding intrinsically-blocked IgG1-hinge ZipR-CAR, rtTA3 (tet transactivator), and Thy1.1 ( FIG. 25A ). Cells were MACS sorted based on FLAG to obtain high purity ZipR-CAR population ( FIG. 25B ). ZipR-CAR expressing T cells with CD19 and CD20 scFv leucine zippers preferentially killed CD19 and CD20 positive targets in the presence of doxycycline (scFvs induced) ( FIG. 25C ). At high E:T ratios, target lysis was seen for CD20 scFv in the absence of doxycycline due to basal activity of the promoter (see panel A, right). T cells were incubated with BM185 firefly luciferase transduced targets with expression of either CD19 or CD20. Target survival was assessed as residual luciferase activity after 24 hours. 
     Example 2—Leucine Zipper-Based Chimeric Costimulatory Receptors (CCRs) Activated by Secreted Immune Checkpoint Blocking scFvs with Conjugated Leucine Zippers and Sorting Affinity Tags 
     Chimeric costimulatory receptors (CCRs) comprises scFv and costimulatory domain but lacks a ZAP70-binding motif such as CD3 zeta. CCRs can induce antigen specific costimulation to T cells, while not sending a TCR-like signal and thus not activating T cell killing function. Traditionally, these molecules comprise a single scFv and are limited to a single target antigen. However, they can be designed using a heterodimerizing leucine zipper to bind multiple Zipper-scFvs ( FIGS. 10 and 11 ). As shown in  FIG. 10 , leucine zipper based CARs and CCRs induce CD3ζ signaling and costimulatory signaling from the same panel of scFvs. T cells can be engineered to express a ZipR-CAR and ZipR-CCR to promote enhanced costimulation in response to the same antigens bound by shared scFv (i.e., both ZipR-CAR and ZipR-CCR use the same leucine zipper in this system). See  FIG. 10 . A different set of scFvs are bound by the ZipR-CAR and ZipR-CCR can also be used to enable AND-gate behavior, e.g., using Fos/Jun or Fos/synZip heterodimers compared to RR12EE345L and EE12RR345L. See  FIG. 10 .  FIG. 11  shows a ZipR-CCR based on CD137 costimulatory signaling domain, and its expression in Tclip hybridoma. Other suitable costimulatory signaling domains include, but not limited to, CD28, ICOS, etc. 
     Antibody mediated blockade of immune regulatory checkpoint molecules such as PD-L1, CTLA-4, CD200, TIM-3, B7-H3, and B7-H4 has been shown in both preclinical and clinical studies to promote immune responses against tumors by blocking negative costimulatory signals delivered to T cells. An alternative approach to blocking these molecules with antibodies is to engineer a T cell by expressing a CCR that binds an immune regulatory checkpoint ligand and delivers a positive costimulatory signal. However, this method is limited by the number of CCR proteins that can be expressed in a single cell. 
     To overcome this limitation, a two-vector system was developed to modify T cells to express scFv-affinity tag-leucine zippers (e.g., RR12EE345L) specific for multiple immune regulatory checkpoint ligands (e.g., PD-L1, CD200, and B7-H4) with corresponding leucine-zipper based CCRs (e.g. EE12RR345L:CD137) ( FIGS. 12-14 ).  FIG. 12  shows ZipR based CCRs having combined checkpoint blockade and T cell costimulatory signaling. T cells can be engineered to secrete scFv-affinity tag-leucine zippers that bind to ZipR-CCRs. One method involves secretion of scFvs that can block immune regulatory checkpoints such as PD-L1 and convert the negative signal normally transduced in response to these molecules into positive costimulatory signals via a switch receptor mechanism.  FIG. 13  shows combined checkpoint blockage and costimulatory switch receptor targeting multiple inhibitory ligands. Negative costimulatory ligands are blocked by secreted scFv-leucine zippers. ZipR-CCR converts negative signal to positive costimulatory signal. Multiplex ZipR-CCR platform allows multiple immune checkpoint ligands to be blocked and converted to positive signaling molecules. As shown in  FIG. 14 , T cells expressing canonical CARs targeting immune checkpoints were able to kill immune-checkpoint molecule-positive targets, which validated scFvs against immune checkpoints. 
     The advantages of this system include: (1) Allowing targeting and blockade of multiple immune checkpoint pathways, (2) converting negative signals into positive costimulatory signals in response to tumor cells or exhausted T cells, and (3) allowing high purity sorting of T cells expressing the constructs. CCR signaling domains can include multiple classes of costimulatory molecules including, but not limited to: CD28 family members (CD28, ICOS), TNF superfamily members (CD134, CD137), and STAT3/STATS activating sequences. This system can enhance both engineered and endogenous immune responses. 
     Example 3—Leucine Zipper-Based Chimeric Costimulatory Receptors (CCRs) Activated by Secreted Cytokines Fusions with Conjugated Leucine Zippers and Sorting Affinity Tags 
     T cells can receive cytokine signals via trans-presentation, in which another cell delivers a cytokine to a T cell via surface presentation (e.g., IL-15). Additionally, artificial antigen presenting cells have been engineered that trans-present cytokines such as IL-15 and IL-21 to T cells for in vitro expansion. 
     The presently disclosed subject matter provides leucine zippers appended to cytokines, such as IL-3, IL-7, IL-15, IL-18 or IL-21, to provide T cell-delivered cytokine stimulation locally ( FIG. 8 ). As shown in  FIG. 8 , IL-3 “zipperkine” converted ZipR-CAR into IL-3-based receptor. IL-3 “zipperkine” comprises IL-3 cytokine with C-terminal FLAG-tag and RR12EE345L leucine zipper. The IL-3 zipperkine was captured by the ZipR-CAR and trans-presented onto the surface of the T cell to generate a receptor that can target cells expressing IL-3R complex. By activating a ZipR-CCR, the cytokine:cytokine-receptor interaction actives the CCR and leads to bi-directional activation ( FIGS. 15 and 16 ), which activates the ZipR-CCR transduced T cells as well as endogenous T cells in the tumor microenvironment and thereby elicits endogenous T cell responses.  FIG. 15  shows ZipR based CCRs with cytokine zippers induced autocrine and paracrine T cell activation. T cells can be co-transduced to express leucine-zipper based costimulatory chimeric receptor (ZipR-CCR) in combination with leucine zipper-tagged cytokines such as IL-15 and IL-21. Surface bound “trans-presented” IL-15 and IL-21 can enhance T cell proliferation and survival. This system can be combined with scFv-zippers targeting surface molecules to promote T cell proliferation, and can be combined with orthogonal ZipR-CAR system for activating T cell killing of target cells.  FIG. 16  shows ZipR based CCRs with cytokine leucine zippers inducing autocrine and paracrine T cell activation. T cells can be engineered to express leucine zipper tagged cytokines, which can promote T cell proliferation, survival, and IFN-gamma production by T cells. IFN-gamma can activate APCs to secrete IL-12 and increase phagocytosis. 
     Example 4—Leucine Zipper-Based Chimeric Costimulatory Receptors (CCRs) Activated by Secreted scFv Leucine Zipper Sorting Affinity Tags that Also Activate Antigen Presenting Cells (APC) 
     Resting APCs result in poor antigen presentation to and activation of T cells and can promote T cell anergy. Activation of APCs has been shown in preclinical models to promote T cell activation, abrogate the requirement for CD4 T cell help, and enhance tumor immunotherapy. As such, a two-vector system is developed to modify T cells to express scFv-affinity tag-leucine zippers specific for activating receptors of APCs (e.g. CD40, Toll Like Receptors (TLRs)) with co-expression of corresponding leucine-zipper based CCRs (e.g. EE12RR345L:CD137) ( FIG. 17 ). As shown in  FIG. 17 , ZipR based CCRs can induce combined antigen presenting cell activation and T cell costimulatory signaling. The system targets costimulatory receptors on surface of antigen presenting cells with affinity tagged scFv leucine zippers, and allows sorting of T cells expressing scFv affinity tags. The scFv leucine zippers can interact with positive costimulatory receptors on antigen presenting cells. This system can promote activation of antigen presenting cells and simultaneously send positive signals to T cells via ZipR-CCRs. This system can promote T cell activation in the setting of alternatively activated macrophages. In another approach, the cells can be sorted using a ZipR-CAR and express orthogonal leucine zippers to interact with CCR. ScFvs can be expressed downstream of NFAT promoter to only express in tumor micro-environment downstream of CAR signaling. 
     Similar to Example 2, this vector system promotes activation and proliferation of T cells by directly delivering a positive costimulatory signal to T cells via CCRs in response to APCs. However, the method also activates APCs to upregulate positive costimulatory molecules (CD80, CD86), enhance peptide presentation, and enhance pro-inflammatory cytokine secretion. This system can be engineered such that the scFv-affinity tag-leucine zippers are expressed only down-stream of CAR-mediated NFAT signaling to limit the activation of APCs to the tumor microenvironment. This system can enhance both engineered and endogenous immune responses. 
     Example 5—Phosphatase-Based Negative Signaling Chimeric Antigen Receptors Forming AND-Logic Gates (AND-CARs) with Leucine Zipper-Based Antigen Recognition Motifs to Allow Combined OR-Logic Gates 
     Non-tumor specificity of tumor associated antigens, with off-tumor on-target toxicity, represents a current limitation of CAR based immunotherapy. One approach to enhance the specificity of a CAR or TCR-based immune response is to limit T cell activation to targets expressing combinations of antigens (AND-gate, e.g. cells expressing HLA-A2 and CD20 in setting of HLA-mismatched allogeneic hematopoietic cell transplant). A prior system has shown that phosphatase-based receptors with large extracellular domains can be selectively activated in response to antigen, allowing T cells to be “licensed” for activity in the presence of the activating antigen, but otherwise inhibited. This system was adapted using CD19 and CD20 antigens as shown in  FIG. 18 . As shown in  FIG. 18 , phosphatase chimeric receptor based AND-gates allowed selective killing of targets by T cells. T cells can be engineered to express phosphatases linked to large extracellular domains spacers bearing scFvs (AND-CAR). If the spacers are designed at a particular size, the constructs are constitutively inhibitory to T cell signaling. However, in the presence of the cognate antigen, the antigen-receptor pair segregates away from TCRs and CARs, and positive signaling of these molecules is licensed. This generates a functional AND-gate. However, this gate is limited to a single antigen specificity conferred by the scFv of the AND-CAR. 
     However, a tumor cell may lose expression of the licensing antigen (e.g., CD20). As such, it is advantageous to enable a T cell to become activated in response to multiple licensing antigens. However, expressing multiple AND-CARs specific for multiple antigens in one cell increases the stringency. Additionally, AND-CAR DNA constructs are large constructs requiring multiple vectors to package all required RNA/DNA, limiting expression of multiple constructs. 
     As such, a leucine zipper-based AND-CAR system is developed (e.g. EE12RR345L IgG1 CD148), where AND-CAR constructs are co-expressed with scFv-affinity tag-leucine leucine zippers specific for multiple licensing antigens to allow sorting and a combined AND/OR gate, e.g., licensing requires antigen HLA-A2 AND (CD20 OR CD22 OR CD123) ( FIG. 19 ). As shown in  FIG. 19 , ZipR-based AND-CAR allows for multiple licensing scFvs, which increases the number of antigens capable of activating T cells. Therefore, an OR-gate is combined with the AND-gate of the AND-CAR. For example, pre-B cell ALL licensing vector containing scFvs against CD19, CD22 and CD123 can be combined with a CAR against HLA-A2 to form an AND-gate, which target cells expressing HLA-A2 and at least one of CD19, CD22 and CD123 (AND-gate+OR-gate). 
     Example 6—ZipR-CAR T Cells as a Chemotherapy-Free, Radiation-Free Conditioning Regimen for Hematopoietic Cell Transplant (HCT) 
     HCT requires a chemotherapy or radiation-based conditioning regimen to kill hematopoietic progenitor cells (HPCs), T cells, B cells, and myeloid cells to facilitate engraftment of donor HPCs and prevent rejection of donor HPCs by host T cells. T cell depleted HCT is a modification of HCT that uses CD34+ selection, myeloablative chemotherapy or radiation, and in vivo host T cell depletion using antithymocyte globulin to compensate for the relative reduction in donor T cells, which normally facilitate engraftment. These conditioning regimens can lead to transplant related mortality and late toxicities including organ dysfunction and secondary malignancies. 
     However, T cells can be modified to attack host T cells, HPCs, T cells, B cells, and myeloid cells to facilitate engraftment. T cells must undergo TCR or CD3 deletion to remove the CD3 antigen from the surface when using CD3 as a target. T cells can be further modified to express cytokines such as IL-12 or IL-18, which have been shown to obviate the need for a conditioning regimen in animal models of leukemia. 
     As such, TCR-deleted ZipR-CAR T cells were generated by expressing IL-18 and iCaspase9 from one vector and expressing scFvs from another vector targeting antigens to delete host hematopoietic elements including HPCs prior to donor HPC infusion ( FIGS. 20 and 21 ).  FIG. 20  and  FIG. 21  show ZipR-CAR based chemotherapy-free HCT conditioning regimen. The system can be used for hematologic malignancies or non-malignant hematologic disorders (e.g., sickle cell anemia). Host T cells, B cells, and NK cells are depleted to prevent rejection of allogeneic donor bone marrow traditionally by chemotherapy and radiation, which are associated with acute and chronic toxicity and risk of secondary malignancies. ZipR-CAR T cells can deplete multiple host hematopoietic cell lineages. ZipR-CAR vector can encode suicide gene to allow T cell depletion and engraftment of donor HPCs. The system can further include scFv targeting CLL-1/CLEC12A to target mature myeloid cells, and can include IL-3 zipperkine or CD123 scFv to target early myeloid cells. T cells can be engineered to secret IL-18 or other cytokines to promote eradiation of host cells. In certain embodiments, TCR is deleted (e.g., by CRISPR, PEBL, or TALEN, etc.) from cell surface to prevent fratricide, e.g., for CD3 CAR. 
     This cell product can be obtained from a universal third-party donor and can be frozen as a cell bank to be infused into any patient as the TCR is deleted, removing the capacity for graft-versus-host disease (GVHD). After the recipient hematopoietic system has been deleted by the ZipR-CAR T cells, the suicide gene can be activated by infusion of a chemical dimerizer of iCaspase9 resulting in deletion of the ZipR-CAR T cells. Donor HPCs can then be infused ( FIG. 21 ). 
     The TCR-deleted ZipR-CAR T cells&#39; ability to kill target cell expressing the following antigen was demonstrated: CD3 ( FIG. 22 ), CD117/kit ( FIG. 23 ), CD19, CD20, IL-3R ( FIG. 9 ), CLL-1/CLEC12A ( FIG. 24 ). As shown in  FIG. 22 , T cells expressing CD3 CAR promoted fratricide. T cells transduced to express CD3-PEBL (protein construct that knocks-down CD3/TCR expression) demonstrated reduced TCR expression as function of Thy1.1 reporter expression (left panel). CD3-CAR expression led to fratricide (loss of TCR-beta+ population, right panel). Combined CD3-CAR+CD3-PEBL transduction (middle panel) promoted loss of TCR-beta+ population with protection of Thy1.1+CD3-CAR T cells. PEBL, CRISPR, or TALEN can be used to eliminate CD3 or TCR expression from T cell surface and allow CD3-CAR to target CD3+ recipient/host T cells without causing fratricide. As shown in  FIG. 23 , T cells expressing Kit-CAR targeting CD117/Kit successfully killed Kit +  tumor cells and mouse bone marrow Kit+ cells. P815 mastocytoma express Kit and was killed by Kit-CAR+ T cells. Mouse LSK bone marrow progenitor cells express Kit and were killed by Kit-CAR+ T cells. As shown in  FIG. 24 , CLL-1/CLEC12A CAR eliminated mouse primary acute myeloid leukemia. Mouse AML cell line was derived from mouse bone marrow transduced with MLL-AF9 translocation, which constitutively expressed CLL-1. Overnight incubation with CLL-1 CAR T cells eliminated AML cells CLL-1 was expressed on mature myeloid cells and CLL-1 CAR T cells can facilitate elimination of host myeloid cells in addition to leukemia. 
     A malignancy specific T cell population can be co-infused as a third-party T cell product at the same time of administering the conditioning-regiment T cell product. The advantages of this approach include targeting multiple antigens using the ZipR-CAR system, using IL-18 to facilitate donor HPC engraftment, and including a suicide gene in the ZipR-CAR vector to permit elimination of the ZipR-CAR T cells to prevent donor HPC graft rejection or long-term cellular aplasias. 
     Example 7—Chemokine-Appended Leucine Zipper Constructs 
     T cells are co-transduced with separate vectors encoding (a) chemokine-appended RR12EE345L leucine zipper and (b) EE12RR345L 28z leucine zipper-based ZipR-CAR, as shown in  FIG. 26A . As shown in  FIG. 26A , CCL17 and CCL22 interact with CCR4; and CCL1 interacts with CCR8. As shown in  FIG. 26B , T cells co-expressing ZipR-CARs and chemokine zippers (zipperkines) mediated target lysis against EL4 expressing CCR4 or CCR8. 
     Embodiments of the Presently Disclosed Subject Matter 
     From the foregoing description, it will be apparent that variations and modifications may be made to the presently disclosed subject matter to adopt it to various usages and conditions. Such embodiments are also within the scope of the following claims. 
     The recitation of a listing of elements in any definition of a variable herein includes definitions of that variable as any single element or combination (or sub-combination) of listed elements. The recitation of an embodiment herein includes that embodiment as any single embodiment or in combination with any other embodiments or fragments thereof. 
     All patents and publications mentioned in this specification are herein incorporated by reference to the same extent as if each independent patent and publication was specifically and individually indicated to be incorporated by reference.