Patent Publication Number: US-2021171596-A1

Title: Untargeted and targeted il-10 fc-fusion proteins

Description:
The application claims the benefit of U.S. Provisional Application No. 62/808,749 filed Feb. 21, 2019 and U.S. Provisional Application No. 62/808,751 filed Feb. 21, 2019, the contents are herein incorporated by reference in their entirety. 
    
    
     SEQUENCE LISTING 
     The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Mar. 31, 2020, is named 067461-5230-US_SL.txt and is 2,370,767 bytes in size. 
     BACKGROUND OF THE INVENTION 
     In order for the immune system to mount an effective anti-tumor response, two things must occur. T cells in the tumor environment must first engage antigenic tumor peptides presented by major histocompatibility complexes (MHC) on tumor cells. Next, the T cells must be induced by cytokines such as IL-15 and IL-2 to produce costimulatory cytokines such as IFNγ. Recognition of tumor peptides alone in the absence of cytokine induction leads to T cells becoming anergic, thereby leading to tolerance. Accordingly, a very promising approach in cancer immunotherapy is cytokine-based treatments. In fact, IL-2 has been approved for use in patients with metastatic renal-cell carcinoma and malignant melanoma. 
     In addition to T cell anergy, tumor cells escape immune response through the downregulation of MHC molecules (Seliger et al., 2002). While interleukin-10 (IL-10) is a cytokine traditionally recognized for its immunoinhibitory properties (Taga, K. and Tosato, G., 1992), it has been found to have immunostimulatory functions in the tumor environment. In line with this, Mumm et al. (2011) reported that IL-10 treatment significantly increases the number of CD8 +  T cells in the tumor microenvironment, the expression of IFNγ and granzymes by said intratumoral CD8 +  T cells, and expression of intratumoral antigen presentation molecules such as MHC-I and MHC-II, all of which are essential mechanisms for an effector antitumor response. 
     The biologically functional IL-10 is a domain-swapped homodimer formed by non-covalent interactions between two IL-10 monomers. The biologically functional IL-10 dimer binds the IL-10 receptor which consists of two alpha and two beta subunits (or R1 and R2 subunits). Notably, the IL-10 dimer becomes biologically inactive upon disruption of the interaction between the individual IL-10 monomers. Additionally, as with other cytokines, IL-10 has a short plasma half-life. Rachmawati et al. (2004) reported that human IL-10 injected in rat underwent rapid initial clearance yielding a half-life of 1.7 minutes. Accordingly, in a first aspect, the present invention addresses potential disruption of the biologically functional IL-10 dimer and its short circulatory half-life by providing IL-10 fusion proteins, as well as novel IL-10 variants engineered with decreased potency. 
     While IL-10 can enhances the immune response, for example in cancer, through stimulation of intratumoral CD8 +  T cells, IL-10 can also potentiate inhibition of the immune response through CD4+ regulatory T cells. In line with this, Chan et al. (2015) reported that IL-10 stimulates secretion of IFNγ by CD8 +  T cells, incubation of IL-10 with bulk PBMCs actually leads to suppression of IFNγ secretion, suggesting that the immunosuppressive effect of IL-10 is potentiated through non-CD8+ lymphocytes. Further, a high CD8/CD4 T cell ratio in TILs is generally considered a good prognostic marker for tumor therapy. Therefore, in another aspect, the present invention provides CD8-targeted IL-10 fusion proteins. 
     Immune checkpoint proteins such as PD-1 are up-regulated following T cell activation to preclude autoimmunity by exhausting activated T cells upon binding to immune checkpoint ligands such as PD-L1. However, immune checkpoint proteins are also up-regulated in tumor-infiltrating lymphocytes (TILs), and immune checkpoint ligands are overexpressed on tumor cells, as another mechanism of immune escape by tumor cells. De-repression of TILs by blockade of immune checkpoint interactions by drugs such as Opdivo® (nivolumab) and Keytruda® (pembrolizumab) have proven highly effective in treatment of cancer. Despite the promise of checkpoint blockade therapies such as nivolumab and pembrolizumab, many patients still fail to achieve sufficient response to checkpoint blockade alone. Accordingly, there is a need to identify therapeutic modalities to stack with checkpoint blockade that could increase patient response rate. This can be especially complex as the additional therapeutic modality should not compete with the checkpoint blockade. Therefore, in yet another aspect, the present invention provides PD-1-targeted IL-10 fusion proteins which are selective for TILs expressing PD-1, and which do not compete with checkpoint blockade antibodies with which they may be combined. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect, the present invention provides a heterodimeric Fc fusion protein comprising: (a) a fusion protein comprising a first protein domain, a second protein domain and a first Fc domain, wherein the first protein domain is covalently attached to the second protein domain, and wherein the second protein domain is covalently attached to the first Fc domain; and (b) a second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains and wherein the first protein domain comprises a first IL-10 monomer domain and the second protein domain comprises a second IL-10 monomer domain. In some instances, the heterodimeric Fc fusion protein has a single-chain IL-10 hetero-Fc fusion or scIL10-heteroFc format. 
     In some embodiments, the second protein domain is covalently attached to the N-terminus of the first Fc domain. In certain embodiments, the second protein domain is covalently attached to the C-terminus of the first Fc domain. In some embodiments, the second protein domain is covalently attached to the first Fc domain via a first domain linker. In some embodiments, the first protein domain is attached to the second protein domain via a second domain linker. 
     In some embodiments, the modifications promoting heterodimerization of the first and the second Fc domains are a set of amino acid substitutions selected from the group consisting of L368D/K370S and S364K; L368D/K370S and S364K/E357L; L368D/K370S and S364K/E357Q; T411E/K360E/Q362E and D401K; L368E/K370S and S364K; K370S and S364K/E357Q and T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C), according to EU numbering. In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions comprising Q295E/N384D/Q418E/N421D, according to EU numbering. In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions consisting of G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. 
     In some embodiments, the heterodimeric Fc fusion protein comprises an amino acid modification of G446del/K4447del in the first and/or second Fc domain. 
     In some embodiments, the second Fc domain and/or second Fc domain comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. 
     In some embodiments, the first and/or second IL-10 monomer domain has a polypeptide sequence selected from the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO:4 (human IL-10 (109L) mature form sequence), as depicted in  FIG. 1 . 
     In some embodiments, the first and/or second IL-10 monomer domain is a variant IL-10 monomer domain. In some embodiments, the variant IL-10 monomer domain comprises an IL-10 monomer domain with one or more amino acid substitutions resulting in altered affinity for an IL-10 receptor, altered potency, altered potential for deamidation, altered potential for aspartic acid isomerization, altered potential for degradation-related PTMs, altered potential degradation sites, altered disulfide bridges, and/or altered potential N-glycosylation sites. 
     In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications at amino acid residues selected from the group consisting of N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, E151, and N160. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications selected from N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, E151Q, and N160del. 
     In some embodiments, the first IL-10 monomer domain covalently attached to the second IL-10 monomer domain form a single chain IL-10 comprising SEQ ID NO:23 or SEQ ID NO:23 with amino acid modifications 109L and 269L. In some embodiments, the single chain IL-10 comprises one or more amino acid modifications selected from the group consisting of N21, Q38, D41, N45, D144, E151, N181, Q198, N205, D304, E311, and N320. 
     In some embodiments, the single chain IL-10 comprises one or more amino acid modifications selected from the group consisting of N21D, Q38E, D41N, N45D, D144N, E151Q, N181D, Q198E, N205D, D304N, E311Q, and N320del. In some embodiments, the single chain IL-10 comprises amino acid modifications selected from N21D/N181D/N320del, N45D/N205D/N320del, Q38E/N45D/N205D/N320del, D41N/N45D/N205D/N320del, N45D/D144N/N205D/N320del, N45D/E151Q/N205D/N320del, N45D/N181D/N205D/N320del, N45D/N205D/D304N/N320del, N21D/N45D/N181D/N205D/N320del, Q38E/N45D/Q198E/N205D/N320del, Q42E/N45D/Q202E/N205D/N320del, and N45D/E151Q/N205D/E311Q/N320del. 
     In some embodiments, the Fc fusion protein (e.g., scIL10-heteroFc fusion protein) is XENP30005 (SEQ ID NOS:25 and 26), XENP30008 (SEQ ID NOS: 27 and 28) or XENP30013 (SEQ ID NOS: 29 and 30) as depicted in  FIGS. 78A-78G . 
     In some embodiments, the Fc fusion protein is a member selected from XENP25239, XENP25240, and XENP25241 as depicted in  FIGS. 21A-21C . 
     Provided herein is a composition comprising a heterodimeric Fc fusion protein (e.g., scIL10-heteroFc fusion protein) outlined herein for use in treating cancer in a subject. Also, provided herein is one or more nucleic acids encoding a heterodimeric Fc fusion protein outlined herein. Also, provided herein is a host cell comprising the one or more nucleic acids encoding a heterodimeric Fc fusion protein outlined herein. 
     In another aspect, provided herein is a method of making a heterodimeric Fc fusion protein (e.g., scIL10-heteroFc fusion protein) comprising culturing any host cell described under conditions, whereby the heterodimeric Fc fusion protein is produced; and recovering the heterodimeric Fc fusion protein. 
     In yet another aspect, provided herein is a method of purifying a heterodimeric Fc fusion protein described herein. The method comprises: (a) providing a composition comprising the heterodimeric Fc fusion protein; (b) loading the composition onto an ion exchange column; and (c) collecting a fraction containing the heterodimeric Fc fusion protein. 
     In another aspect, the present invention provides a heterodimeric Fc fusion protein comprising: (a) a first fusion protein comprising an antigen binding domain (ABD) and a first Fc domain, wherein the antigen binding domain is attached to the N-terminus of the first Fc domain; and (b) a second fusion protein comprising a first protein domain, a second protein domain and a second Fc domain, wherein the first protein domain is covalently attached to the second protein domain, and wherein the second protein domain is covalently attached to the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first protein domain comprises a first IL-10 monomer domain and the second protein domain comprises a second IL-10 monomer domain. In some instances, the heterodimeric Fc fusion protein has an anti-X× single-chain IL-10 hetero-Fc fusion or anti-X×scIL10-heteroFc format. In some embodiments, the IL-10 monomer of the scIL10 is linked to the N-terminus or C-terminus of the Fc domain. 
     In some embodiments, the second protein domain (e.g., second IL-10 monomer domain) is covalently attached to the N-terminus of the second Fc domain. In some embodiments, the second protein domain is covalently attached to the C-terminus of the second Fc domain. In some embodiments, the first protein domain (e.g., first IL-10 monomer domain) is attached to the second protein domain (e.g., second IL-10 monomer) using a first domain linker. In some embodiments, the antigen binding domain is attached to the first Fc domain using a second domain linker. 
     In some embodiments, the modifications promoting heterodimerization of the first and the second Fc domains are a set of amino acid substitutions selected from the group consisting of L368D/K370S and S364K; L368D/K370S and S364K/E357L; L368D/K370S and S364K/E357Q; T411E/K360E/Q362E and D401K; L368E/K370S and S364K; K370S and S364K/E357Q and T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C), according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions comprising Q295E/N384D/Q418E/N421D, according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions consisting of G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. 
     In some embodiments, the first Fc domain and/or the second Fc domain comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. 
     In some embodiments, the first and/or the second IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO:4 (human IL-10 (109L) mature form sequence), as depicted in  FIG. 1 . 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain is a variant IL-10 monomer domain. 
     In some embodiments, the variant IL-10 monomer domain comprises an IL-10 monomer domain with one or more amino acid substitutions resulting in altered affinity for an IL-10 receptor, altered potency, altered potential for deamidation, altered potential for aspartic acid isomerization, altered potential for degradation-related PTMs, altered potential degradation sites, altered disulfide bridges, and/or altered potential N-glycosylation sites. 
     In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications at amino acid residues selected from the group consisting of N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, E151, and N160. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications selected from N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, E151Q, and N160del. 
     In some embodiments, the first IL-10 monomer domain covalently attached to the second IL-10 monomer domain form a single chain IL-10 comprising SEQ ID NO:23 or SEQ ID NO:23 with amino acid modifications 109L and 269L. In some embodiments, the single chain IL-10 further comprises one or more amino acid modifications selected from the group consisting of N21, Q38, D41, N45, D144, E151, N181, Q198, N205, D304, E311, and N320. In some embodiments, the single chain IL-10 further comprises one or more amino acid modifications selected from the group consisting of N21D, Q38E, D41N, N45D, D144N, E151Q, N181D, Q198E, N205D, D304N, E311Q, and N320del. In some embodiments, the single chain IL-10 comprises amino acid modifications selected from N21D/N181D/N320del, N45D/N205D/N320del, Q38E/N45D/N205D/N320del, D41N/N45D/N205D/N320del, N45D/D144N/N205D/N320del, N45D/E151Q/N205D/N320del, N45D/N181D/N205D/N320del, N45D/N205D/D304N/N320del, N21D/N45D/N181D/N205D/N320del, Q38E/N45D/Q198E/N205D/N320del, Q42E/N45D/Q202E/N205D/N320del, and N45D/E151Q/N205D/E311Q/N320del. 
     In some embodiments, the antigen binding domain (ABD) is selected from the group consisting of a PD-1 binding domain, a non-competing PD-1 binding domain, a TIGIT binding domain, a CD8 binding domain, and a NKG2D binding domain. 
     In some embodiments, the PD-1 binding domain is a humanized PD-1 ABD. In some embodiments, the humanized PD-1 ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting of: 1C11[PD-1]_H0L0, 1C11[P, D-1]_H3L3, 1C11[PD-1]_H3.240_L3.148, 1C11[PD-1]_H3.241_L3.148, 1C11[PD-1]_H3.234_L3.144, 1C11[PD-1]_H3.241_L3.92, 1C11[PD-1]_H3.303_L3.152, 1C11_H3.329_L3.220, 1C11_H3.328_L3.152, pembrolizumab variable heavy chain and variable light chain, nivolumab variable heavy chain and variable light chain, pidilizumab variable heavy chain and variable light chain, MK-3475 variable heavy chain and variable light chain, BAP049 Clone E variable heavy chain and variable light chain, BAP049 Clone B variable heavy chain and variable light chain, H7798N[PD-1] variable heavy chain and variable light chain, h1H3 Var 6[PD-1] variable heavy chain and variable light chain, APE2058[PD-1] variable heavy chain and variable light chain, H005-1[PD-1] variable heavy chain and variable light chain, 317-4B6[PD-1] variable heavy chain and variable light chain, 326-4A3[PD-1] variable heavy chain and variable light chain, hPD-1 mAb 7 (1.2)[PD-1] variable heavy chain and variable light chain, Clone 38[PD-1] variable heavy chain and variable light chain, Clone 39[PD-1] variable heavy chain and variable light chain, Clone 41[PD-1] variable heavy chain and variable light chain, Clone 48[PD-1] variable heavy chain and variable light chain, PD1-17[PD-1] variable heavy chain and variable light chain, PD1-28[PD-1] variable heavy chain and variable light chain, PD1-33[PD-1] variable heavy chain and variable light chain, PD1-35[PD-1] variable heavy chain and variable light chain, LOPD180 variable heavy chain and variable light chain, Ab948 variable heavy chain and variable light chain, humanized EH-12.2H7[PD-1] variable heavy chain and variable light chain, RG1H10 variable heavy chain and variable light chain, RG1H10-H2A-22-1S variable heavy chain and variable light chain, RG1H10-H2A-27-2S variable heavy chain and variable light chain, RG1H10-3C variable heavy chain and variable light chain, RG1H10-16C variable heavy chain and variable light chain, RG1H10-17C variable heavy chain and variable light chain, RG1H10-19C variable heavy chain and variable light chain, RG1H10-21C variable heavy chain and variable light chain, RG1H10-23C2 variable heavy chain and variable light chain, mAb7[PD-1], and PD1AB-6[PD-1] variable heavy chain and variable light chain, as depicted in  FIGS. 100A-100G . 
     In some embodiments, the heterodimeric Fc fusion protein that binds PD-1 (e.g., anti-PD-1×scIL10-hetero Fc) is a member selected from the group consisting of: XENP25953, XENP27830, and XENP27831. 
     In some embodiments, the non-competing PD-1 binding domain is a humanized non-competing PD1 ABD that does not bind the same epitope as nivolumab and/or pembrolizumab. In some embodiments, the humanized non-competing PD-1 ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting of: mAb A[PD-1]_H1_L1, mAb B[PD-1]_H1_L1, mAb C[PD-1]_H1_L1, mAb C[PD-1]_H1_L1.1, mAb C[PD-1]_H1_L1.3, mAb C[PD-1]_H1_L1.45, mAb C[PD-1]_H1_L1.117, mAb C[PD-1]_H1_L1.129, mAb C[PD-1]_H1_L1.135, mAb C[PD-1]_H1_L1.136, mAb C[PD-1]_H1_L1.140, mAb C[PD-1]_H1_L2, mAb C[PD-1]_H1.19_11, mAb C[PD-1]_H1.19_L1.1, mAb C[PD-1]_H1.19_L1.3, mAb C[PD-1]_H1.19_L1.45, mAb C[PD-1]_H1.19_L1.117, mAb C[PD-1]_H1.19_L1.129, mAb C[PD-1]_H1.19_L1.135, mAb C[PD-1]_H1.19_L1.136, mAb C[PD-1]_H1.19_L1.140, mAb C[PD-1]_H1.19_L2, mAb C[PD-1]_H1.48_11, mAb C[PD-1]_H1.48_L1.1, mAb C[PD-1]_H1.48_L1.3, mAb C[PD-1]_H1.48_L1.45, mAb C[PD-1]_H1.48_L1.117, mAb C[PD-1]_H1.48_L1.129, mAb C[PD-1]_H1.48_L1.135, mAb C[PD-1]_H1.48_L1.136, mAb C[PD-1]_H1.48_L1.140, mAb C[PD-1]_H1.48_L2, mAb C[PD-1]_H1.125_11, mAb C[PD-1]_H1.125_L1.1, mAb C[PD-1]_H1.125_L1.3, mAb C[PD-1]_H1.125_L1.45, mAb C[PD-1]_H1.125_L1.117, mAb C[PD-1]_H1.125_L1.129, mAb C[PD-1]_H1.125_L1.135, mAb C[PD-1]_H1.125_L1.136, mAb C[PD-1]_H1.125_L1.140, mAb C[PD-1]_H1.125_L2, mAb C[PD-1]_H1.130_11, mAb C[PD-1]_H1.130_L1.1, mAb C[PD-1]_H1.130_L1.3, mAb C[PD-1]_H1.130_L1.45, mAb C[PD-1]_H1.130_L1.117, mAb C[PD-1]_H1.130_L1.129, mAb C[PD-1]_H1.130_L1.135, mAb C[PD-1]_H1.130_L1.136, mAb C[PD-1]_H1.130_L1.140, mAb C[PD-1]_H1.130_L2, mAb C[PD-1]_H1.132_11, mAb C[PD-1]_H1.132_L1.1, mAb C[PD-1]_H1.132_L1.3, mAb C[PD-1]_H1.132_L1.45, mAb C[PD-1]_H1.132_L1.117, mAb C[PD-1]_H1.132_L1.129, mAb C[PD-1]_H1.132_L1.135, mAb C[PD-1]_H1.132_L1.136, mAb C[PD-1]_H1.132_L1.140, mAb C[PD-1]_H1.132_L2, mAb C[PD-1]_H1.169_11, mAb C[PD-1]_H1.169_L1.1, mAb C[PD-1]_H1.169_L1.3, mAb C[PD-1]_H1.169_L1.45, mAb C[PD-1]_H1.169_L1.117, mAb C[PD-1]_H1.169_L1.129, mAb C[PD-1]_H1.169_L1.135, mAb C[PD-1]_H1.169_L1.136, mAb C[PD-1]_H1.169_L1.140, mAb C[PD-1]_H1.169_L2, mAb C[PD-1]_H1.175_11, mAb C[PD-1]_H1.175_L1.1, mAb C[PD-1]_H1.175_L1.3, mAb C[PD-1]_H1.175_L1.45, mAb C[PD-1]_H1.175_L1.117, mAb C[PD-1]_H1.175_L1.129, mAb C[PD-1]_H1.175_L1.135, mAb C[PD-1]_H1.175_L1.136, mAb C[PD-1]_H1.175_L1.140, mAb C[PD-1]_H1.175_L2, mAb C[PD-1]_H2_L1, mAb C[PD-1]_H2_L1.1, mAb C[PD-1]_H2_L1.3, mAb C[PD-1]_H2_L1.45, mAb C[PD-1]_H2_L1.117, mAb C[PD-1]_H2_L1.129, mAb C[PD-1]_H2_L1.135, mAb C[PD-1]_H2_L1.136, mAb C[PD-1]_H2_L1.140, and mAb C[PD-1]_H2_L2, as depicted in  FIGS. 104A-104B . 
     In some embodiments, the CD8 binding domain is a humanized CD8 ABD. In some embodiments, the humanized CD8 ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting OKT8_H2L1 and 1C11B3_H1L1, as depicted in  FIG. 92 . 
     In some embodiments, the NKG2D binding domain is a humanized NKG2D ABD. In some embodiments, the humanized NKG2D ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting MS[NKG2D] H0_L0, 1D7B4[NKG2D]_H1_L1, KYK-1.0[NKG2D]_H1_L1, KYK-2.0[NKG2D]_H0_L0, 11B2D10[NKG2D]_H0_L0, 6E5A7[NKG2D]_H0_L0, 6H7E7[NKG2D]_H0_L0, mAb E[NKG2D]_H1_L1, 16F31[NKG2D]_H1_L1, mAb D[NKG2D]_H1_L1, 1 D7B4[NKG2D]_H1_L1, mAb A[NKG2D]_H1_L1, mAb A[NKG2D]_H2_L1, mAb A[NKG2D]_H1_L2, mAb A[NKG2D]_H2_L2, mAb B[NKG2D]_H1_L1, mAb B[NKG2D]_H1_L1.1, mAb B[NKG2D]_H1_L2, mAb B[NKG2D]_H2_L1, mAb B[NKG2D]_H2_L1.1, mAb B[NKG2D]_H2_L2, mAb B[NKG2D]_H3_L1, mAb B[NKG2D]_H3_L1.1, mAb B[NKG2D]_H3_L2, mAb C[NKG2D]_H1_L1, mAb C[NKG2D]_H2_L1, mAb C[NKG2D]_H1_L2, and mAb C[NKG2D]_H2_L2, as depicted in  FIGS. 93A-93C . 
     Provided herein is a composition comprising a heterodimeric Fc fusion protein (e.g., anti-X×scIL10-heteroFc fusion protein) described for use in treating cancer in a subject. Also, provided is one or more nucleic acids encoding any of the heterodimeric Fc fusion proteins described herein. Also, provided is a host cell comprising one or more nucleic acids encoding any of the heterodimeric Fc fusion proteins described herein. 
     In one aspect, provided is a method of making a heterodimeric Fc fusion protein e.g., anti-X×scIL10-heteroFc fusion protein) comprising culturing a host cell described herein under conditions whereby the heterodimeric Fc fusion protein is produced; and recovering the protein. 
     In another aspect, provided is a method of purifying a heterodimeric Fc fusion protein (e.g., anti-X×scIL10-heteroFc fusion protein) described herein. The method comprises: (a) providing a composition comprising the heterodimeric Fc fusion protein; (b) loading the composition onto an ion exchange column; and (c) collecting a fraction containing the heterodimeric Fc fusion protein. 
     In yet another aspect, the present invention provides a heterodimeric Fc fusion protein comprising: (a) a first fusion protein comprising a first antigen binding domain and a first Fc domain, wherein the first antigen binding domain (ABD) is covalently attached to the N-terminus of the first Fc domain; and (b) a second fusion protein comprising a second antigen binding domain (ABD), a second Fc domain, a first protein domain and a second protein domain, wherein the second antigen binding domain is covalently attached to the N-terminus of the second Fc domain, wherein the first protein domain is covalently attached to the second protein domain, and wherein the second protein domain is covalently attached to the C-terminus of the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first protein domain comprises a first IL-10 monomer domain and the second protein domain comprises a second IL-10 monomer domain. In some instances, the heterodimeric Fc fusion protein has an (anti-X)2× heteroFc-single chain IL-10 fusion or (anti-X)2-heteroFc-scIL10 fusion format. 
     In some embodiments, the modifications promoting heterodimerization of the first and the second Fc domains are a set of amino acid substitutions selected from the group consisting of L368D/K370S and S364K; L368D/K370S and S364K/E357L; L368D/K370S and S364K/E357Q; T411E/K360E/Q362E and D401K; L368E/K370S and S364K; K370S and S364K/E357Q and T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C), according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions comprising Q295E/N384D/Q418E/N421D, according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions consisting of G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. 
     In some embodiments, the first Fc domain and/or the second Fc domain comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. 
     In some embodiments, the first and/or the second IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO:4 (human IL-10 (109L) mature form sequence), as depicted in  FIG. 1 . 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain is a variant IL-10 monomer domain. 
     In some embodiments, the variant IL-10 monomer domain comprises an IL-10 monomer domain with one or more amino acid substitutions resulting in altered affinity for an IL-10 receptor, altered potency, altered potential for deamidation, altered potential for aspartic acid isomerization, altered potential for degradation-related PTMs, altered potential degradation sites, altered disulfide bridges, and/or altered potential N-glycosylation sites. 
     In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications at amino acid residues selected from the group consisting of N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, E151, and N160. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications selected from N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, E151Q, and N160del. 
     In some embodiments, the first IL-10 monomer domain covalently attached to the second IL-10 monomer domain form a single chain IL-10 comprising SEQ ID NO:23 or SEQ ID NO:23 with amino acid modifications 109L and 269L. 
     In some embodiments, the single chain IL-10 further comprises one or more amino acid modifications selected from the group consisting of N21, Q38, D41, N45, D144, E151, N181, Q198, N205, D304, E311, and N320. In some embodiments, the single chain IL-10 further comprises one or more amino acid modifications selected from the group consisting of N21D, Q38E, D41N, N45D, D144N, E151Q, N181D, Q198E, N205D, D304N, E311Q, and N320del. In some embodiments, the single chain IL-10 comprises amino acid modifications selected from N21D/N181D/N320del, N45D/N205D/N320del, Q38E/N45D/N205D/N320del, D41N/N45D/N205D/N320del, N45D/D144N/N205D/N320del, N45D/E151Q/N205D/N320del, N45D/N181D/N205D/N320del, N45D/N205D/D304N/N320del, N21D/N45D/N181D/N205D/N320del, Q38E/N45D/Q198E/N205D/N320del, Q42E/N45D/Q202E/N205D/N320del, and N45D/E151Q/N205D/E311Q/N320del. 
     In some embodiments, the first ABD and/or the second ABD is selected from the group consisting of a PD-1 binding domain, a non-competing PD-1 binding domain, a TIGIT binding domain, a CD8 binding domain, and a NKG2D binding domain. 
     In some embodiments, the PD-1 binding domain is a humanized PD-1 ABD. In some embodiments, the humanized PD-1 ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting of: 1C11[PD-1]_H0L0, 1C11[P, D-1]_H3L3, 1C11[PD-1]_H3.240_L3.148, 1C11[PD-1]_H3.241_L3.148, 1C11[PD-1]_H3.234_L3.144, 1C11[PD-1]_H3.241_L3.92, 1C11[PD-1]_H3.303_L3.152, 1C11_H3.329_L3.220, 1C11_H3.328_L3.152, pembrolizumab variable heavy chain and variable light chain, nivolumab variable heavy chain and variable light chain, pidilizumab variable heavy chain and variable light chain, MK-3475 variable heavy chain and variable light chain, BAP049 Clone E variable heavy chain and variable light chain, BAP049 Clone B variable heavy chain and variable light chain, H7798N[PD-1] variable heavy chain and variable light chain, h1H3 Var 6[PD-1] variable heavy chain and variable light chain, APE2058[PD-1] variable heavy chain and variable light chain, H005-1[PD-1] variable heavy chain and variable light chain, 317-4B6[PD-1] variable heavy chain and variable light chain, 326-4A3[PD-1] variable heavy chain and variable light chain, hPD-1 mAb 7 (1.2)[PD-1] variable heavy chain and variable light chain, Clone 38[PD-1] variable heavy chain and variable light chain, Clone 39[PD-1] variable heavy chain and variable light chain, Clone 41[PD-1] variable heavy chain and variable light chain, Clone 48[PD-1] variable heavy chain and variable light chain, PD1-17[PD-1] variable heavy chain and variable light chain, PD1-28[PD-1] variable heavy chain and variable light chain, PD1-33[PD-1] variable heavy chain and variable light chain, PD1-35[PD-1] variable heavy chain and variable light chain, LOPD180 variable heavy chain and variable light chain, Ab948 variable heavy chain and variable light chain, humanized EH-12.2H7[PD-1] variable heavy chain and variable light chain, RG1H10 variable heavy chain and variable light chain, RG1H10-H2A-22-1S variable heavy chain and variable light chain, RG1H10-H2A-27-2S variable heavy chain and variable light chain, RG1H10-3C variable heavy chain and variable light chain, RG1H10-16C variable heavy chain and variable light chain, RG1H10-17C variable heavy chain and variable light chain, RG1H10-19C variable heavy chain and variable light chain, RG1H10-21C variable heavy chain and variable light chain, RG1H10-23C2 variable heavy chain and variable light chain, mAb7[PD-1], and PD1AB-6[PD-1] variable heavy chain and variable light chain, as depicted in  FIGS. 100A-100G . 
     In some embodiments, the non-competing PD-1 binding domain is a humanized non-competing PD1 ABD that does not bind the same epitope as nivolumab and/or pembrolizumab. In some embodiments, the humanized non-competing PD-1 ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting of: mAb A[PD-1]_H1_L1, mAb B[PD-1]_H1_L1, mAb C[PD-1]_H1_L1, mAb C[PD-1]_H1_L1.1, mAb C[PD-1]_H1_L1.3, mAb C[PD-1]_H1_L1.45, mAb C[PD-1]_H1_L1.117, mAb C[PD-1]_H1_L1.129, mAb C[PD-1]_H1_L1.135, mAb C[PD-1]_H1_L1.136, mAb C[PD-1]_H1_L1.140, mAb C[PD-1]_H1_L2, mAb C[PD-1]_H1.19_11, mAb C[PD-1]_H1.19_L1.1, mAb C[PD-1]_H1.19_L1.3, mAb C[PD-1]_H1.19_L1.45, mAb C[PD-1]_H1.19_L1.117, mAb C[PD-1]_H1.19_L1.129, mAb C[PD-1]_H1.19_L1.135, mAb C[PD-1]_H1.19_L1.136, mAb C[PD-1]_H1.19_L1.140, mAb C[PD-1]_H1.19_L2, mAb C[PD-1]_H1.48_11, mAb C[PD-1]_H1.48_L1.1, mAb C[PD-1]_H1.48_L1.3, mAb C[PD-1]_H1.48_L1.45, mAb C[PD-1]_H1.48_L1.117, mAb C[PD-1]_H1.48_L1.129, mAb C[PD-1]_H1.48_L1.135, mAb C[PD-1]_H1.48_L1.136, mAb C[PD-1]_H1.48_L1.140, mAb C[PD-1]_H1.48_L2, mAb C[PD-1]_H1.125_11, mAb C[PD-1]_H1.125_L1.1, mAb C[PD-1]_H1.125_L1.3, mAb C[PD-1]_H1.125_L1.45, mAb C[PD-1]_H1.125_L1.117, mAb C[PD-1]_H1.125_L1.129, mAb C[PD-1]_H1.125_L1.135, mAb C[PD-1]_H1.125_L1.136, mAb C[PD-1]_H1.125_L1.140, mAb C[PD-1]_H1.125_L2, mAb C[PD-1]_H1.130_11, mAb C[PD-1]_H1.130_L1.1, mAb C[PD-1]_H1.130_L1.3, mAb C[PD-1]_H1.130_L1.45, mAb C[PD-1]_H1.130_L1.117, mAb C[PD-1]_H1.130_L1.129, mAb C[PD-1]_H1.130_L1.135, mAb C[PD-1]_H1.130_L1.136, mAb C[PD-1]_H1.130_L1.140, mAb C[PD-1]_H1.130_L2, mAb C[PD-1]_H1.132_11, mAb C[PD-1]_H1.132_L1.1, mAb C[PD-1]_H1.132_L1.3, mAb C[PD-1]_H1.132_L1.45, mAb C[PD-1]_H1.132_L1.117, mAb C[PD-1]_H1.132_L1.129, mAb C[PD-1]_H1.132_L1.135, mAb C[PD-1]_H1.132_L1.136, mAb C[PD-1]_H1.132_L1.140, mAb C[PD-1]_H1.132_L2, mAb C[PD-1]_H1.169_11, mAb C[PD-1]_H1.169_L1.1, mAb C[PD-1]_H1.169_L1.3, mAb C[PD-1]_H1.169_L1.45, mAb C[PD-1]_H1.169_L1.117, mAb C[PD-1]_H1.169_L1.129, mAb C[PD-1]_H1.169_L1.135, mAb C[PD-1]_H1.169_L1.136, mAb C[PD-1]_H1.169_L1.140, mAb C[PD-1]_H1.169_L2, mAb C[PD-1]_H1.175_11, mAb C[PD-1]_H1.175_L1.1, mAb C[PD-1]_H1.175_L1.3, mAb C[PD-1]_H1.175_L1.45, mAb C[PD-1]_H1.175_L1.117, mAb C[PD-1]_H1.175_L1.129, mAb C[PD-1]_H1.175_L1.135, mAb C[PD-1]_H1.175_L1.136, mAb C[PD-1]_H1.175_L1.140, mAb C[PD-1]_H1.175_L2, mAb C[PD-1]_H2_L1, mAb C[PD-1]_H2_L1.1, mAb C[PD-1]_H2_L1.3, mAb C[PD-1]_H2_L1.45, mAb C[PD-1]_H2_L1.117, mAb C[PD-1]_H2_L1.129, mAb C[PD-1]_H2_L1.135, mAb C[PD-1]_H2_L1.136, mAb C[PD-1]_H2_L1.140, and mAb C[PD-1]_H2_L2, as depicted in  FIGS. 104A-104B . 
     In some embodiments, the CD8 binding domain is a humanized CD8 ABD. In some embodiments, the humanized CD8 ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting OKT8_H2L1 and 1C11B3_H1L1, as depicted in  FIG. 92 . 
     In some embodiments, the NKG2D binding domain is a humanized NKG2D ABD. In some embodiments, the humanized NKG2D ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting MS[NKG2D] H0_L0, 1D7B4[NKG2D]_H1_L1, KYK-1.0[NKG2D]_H1_L1, KYK-2.0[NKG2D]_H0_L0, 11B2D10[NKG2D]_H0_L0, 6E5A7[NKG2D]_H0_L0, 6H7E7[NKG2D]_H0_L0, mAb E[NKG2D]_H1_L1, 16F31[NKG2D]_H1_L1, mAb D[NKG2D]_H1_L1, 1 D7B4[NKG2D]_H1_L1, mAb A[NKG2D]_H1_L1, mAb A[NKG2D]_H2_L1, mAb A[NKG2D]_H1_L2, mAb A[NKG2D]_H2_L2, mAb B[NKG2D]_H1_L1, mAb B[NKG2D]_H1_L1.1, mAb B[NKG2D]_H1_L2, mAb B[NKG2D]_H2_L1, mAb B[NKG2D]_H2_L1.1, mAb B[NKG2D]_H2_L2, mAb B[NKG2D]_H3_L1, mAb B[NKG2D]_H3_L1.1, mAb B[NKG2D]_H3_L2, mAb C[NKG2D]_H1_L1, mAb C[NKG2D]_H2_L1, mAb C[NKG2D]_H1_L2, and mAb C[NKG2D]_H2_L2, as depicted in  FIGS. 93A-93C . 
     Provided is a composition comprising any of the heterodimeric Fc fusion proteins (e.g., anti-X)2-heteroFc-scIL10 fusions) outlined herein for use in treating cancer in a subject. Also provided is one or more nucleic acids encoding any of the heterodimeric Fc fusion proteins outlined herein. Also provided is a host cell comprising one or more nucleic acids encoding any of the heterodimeric Fc fusion proteins outlined herein. 
     In one aspect, provided is a method of making any of the heterodimeric Fc fusion proteins (e.g., anti-X)2-heteroFc-scIL10 fusions) outlined herein comprising culturing a host cell as outlined under conditions whereby the heterodimeric Fc fusion protein is produced; and recovering the protein. 
     In yet another aspect, the present invention provides a dimeric Fc fusion protein comprising: (a) a first fusion protein comprising a first IL-10 monomer domain and a first Fc domain, wherein the IL-10 monomer domain is covalently attached to the first Fc domain; and (b) a second fusion protein comprising a second IL-10 monomer domain and a second Fc domain, wherein the second IL-10 monomer domain is covalently attached the second Fc domain. In some embodiments, the dimeric Fc fusion has a (IL-10)2-Fc fusion format. 
     In some embodiments, the first and second fusion proteins are identical. In some embodiments, the first IL-10 monomer domain and the second IL-10 monomer domain are identical. 
     In some embodiments, the first and/or second Fc domains comprise a set of amino acid substitutions selected from the group consisting of C219S, C220S, S228P, G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions comprising Q295E/N384D/Q418E/N421D, according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions consisting of G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. 
     In some embodiments, the first and/or second Fc domains comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. 
     In some embodiments, the first IL-10 monomer domain is covalently attached to the N-terminus of the first Fc domain and the second IL-10 monomer domain is covalently attached to the N-terminus of the second Fc domain. In certain embodiments, the e first IL-10 monomer domain is covalently attached to the C-terminus of the first Fc domain and the second IL-10 monomer domain is covalently attached to the C-terminus of the second Fc domain. 
     In some embodiments, the first IL-10 monomer domain is attached to the first Fc domain using a first domain linker and/or the second IL-10 monomer domain is attached to the second Fc domain using a second domain linker. In particular embodiments, the first IL-10 monomer domain is attached to the first Fc domain using a first domain linker and the second IL-10 monomer domain is attached to the second Fc domain using a second domain linker. In further embodiments, the first IL-10 monomer domain is attached to the first Fc domain using a first domain linker. In yet further embodiments, the second IL-10 monomer domain is attached to the second Fc domain using a second domain linker. 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain have a leucine at position 109 rather than a histidine. In other words, in some embodiments the first IL-10 monomer domain has a leucine at position 109 rather than a histidine. In some embodiments, the second IL-10 monomer domain has a leucine at position 109 rather than a histidine. In some embodiments, the first IL-10 monomer domain and the second IL-10 monomer domain have a leucine at position 109 rather than a histidine 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain have a histidine at position 109 rather than a leucine. In other words, in some embodiments the first IL-10 monomer domain and the second IL-10 monomer domain have a histidine at position 109 rather than a leucine. In certain embodiments, the first IL-10 monomer domain has a histidine at position 109 rather than a leucine. In other embodiments, the second IL-10 monomer domain has a histidine at position 109 rather than a leucine. 
     In some embodiments, the first and/or second IL-10 monomer domains comprise a polypeptide sequence selected from the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO: 4 (human IL-10 (109L) mature form sequence). In some embodiments, the first IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO: 4 (human IL-10 (109L) mature form sequence). In certain embodiments, the second IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO: 4 (human IL-10 (109L) mature form sequence). 
     In some embodiments, the first and/or second IL-10 monomer domain is a variant IL-10 monomer domain. In some embodiments, the first IL-10 monomer domain is a variant IL-10 monomer domain. In some embodiments, the second IL-10 monomer domain is a variant IL-10 monomer domain. 
     In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications at amino acid residues selected from the group consisting of N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, E151, and N160. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications selected from the group consisting of N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, E151Q, and N160del. 
     In some embodiments, the first and second fusion protein of the (IL-10)2-Fc fusion format each comprises a polypeptide sequence selected from the group consisting of: XENP24628, XENP24629, XENP24630, XENP24631, XENP24632, XENP24633, and XENP24634 as depicted in  FIGS. 17-18 . 
     In one aspect, the present invention provides a heterodimeric Fc fusion protein comprising: a) a first fusion protein comprising a first IL-10 monomer domain and a first Fc domain, wherein the first IL-10 monomer domain is covalently attached to the first Fc domain; and (b) a second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains. In some embodiments, the heterodimeric Fc fusion protein has a (IL10-NC-IL10)-heteroFc fusion format. 
     In some embodiments, the heterodimeric Fc fusion protein further comprises a second IL-10 monomer domain non-covalently attached to the first IL-10 monomer domain. In some embodiments, the first IL-10 monomer domain is attached to the N-terminus of the first Fc domain. In some embodiments, the first IL-10 monomer domain is attached to the C-terminus of the first Fc domain. In some embodiments, the first IL-10 monomer domain is attached to the first Fc domain using a first domain linker. 
     In some embodiments, the modifications promoting heterodimerization of the first and second Fc domains are a set of amino acid substitutions selected from the group consisting of L368D/K370S and S364K; L368D/K370S and S364K/E357L; L368D/K370S and S364K/E357Q; T411E/K360E/Q362E and D401K; L368E/K370S and S364K; K370S and S364K/E357Q and T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C), according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains has an additional set of amino acid substitutions comprising Q295E/N384D/Q418E/N421D, according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions consisting of G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. 
     In some embodiments, the first and/or second Fc domains comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. 
     In some embodiments, the first and/or second IL-10 monomer domain has a polypeptide sequence selected form the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO:4 (human IL-10 (109L) mature form sequence). 
     In some embodiments, the first and/or second IL-10 monomer domain is a variant IL-10 monomer domain. In some embodiments, the variant IL-10 monomer domain comprises an IL-10 monomer domain with one or more amino acid substitutions resulting in altered affinity for an IL-10 receptor, altered potency, altered potential for deamidation, altered potential for aspartic acid isomerization, altered potential for degradation-related PTMs, altered potential degradation sites, altered disulfide bridges, and/or altered potential N-glycosylation sites. 
     In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications at amino acid residues selected from the group consisting of N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, E151, and N160. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications selected from the group consisting of N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, E151Q, and N160del. 
     In yet another aspect, the present invention provides a dimeric Fc fusion protein comprising: (a) a first fusion protein comprising a first protein domain and a first Fc domain, wherein the first protein domain is covalently attached to the first Fc domain; (b) a second fusion protein comprising a second protein domain and a second Fc domain, wherein the second protein domain is covalently attached to the second Fc domain; wherein the first protein domain comprises a first IL-10 monomer domain comprising an insert peptide and the second protein domain comprises a second IL-10 monomer domain comprising an insert peptide. Such a dimeric Fc fusion protein has a (IL10M1)2-Fc fusion format. 
     In some embodiments, the first protein domain is covalently attached to the N-terminus of the first Fc domain and/or the second protein domain is covalently attached to the N-terminus of the second Fc domain. In some embodiments, the first protein domain is covalently attached to the C-terminus of the first Fc domain and/or the second protein domain is covalently attached to the C-terminus of the second Fc domain. In some embodiments, the first protein domain is covalently attached to the first Fc domain via a first domain linker. In some embodiments, the second protein domain is covalently attached to the second Fc domain via a second domain linker. 
     In some embodiments, the first Fc domain and/or the second Fc domain comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. 
     In some embodiments, the insert peptide comprises a domain linker engineered between helices D and E of an IL-10 monomer domain. 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:24 (IL10M1) as depicted in  FIG. 15D  and huIL10M1 variants as depicted in  FIGS. 75A-75B . 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain comprises a variant IL-10 domain comprising one or more amino acid modifications selected from the group consisting of N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, E151Q, C12A, C108A, Q38E/D41N, Q38E/Q42E, Q38E/N45D, Q38E/E142Q, Q38E/D144N, D41N/Q42E, D41N/N45D, D41N/E142Q, D41N/D144N, Q42E/N45D, Q42E/E142Q, Q42E/D144N, N45D/E142Q, N45D/D144N, E142Q/D144N, N21D/Q42E, N21D/N45D, N21D/E151Q, N21D/N45E, Q42E/E151Q, N45D/E151Q, N21D/Q42E/N45D, N21D/Q42E/E151Q, Q42E/N45D/E151Q, N21D/Q42E/N45E, N21D/Q42E/N45D/E151Q, F37C/M140C, Q38C/S141C, D41C/K138C, L47C/K138C, L48C/E142C, S51C/A120C, D55C/A120C, F56C/Y153C, C62A/C114A, A64C/S118C, M68C/V121C, V76C/A139C, L47Q, S118A, and A139Q. 
     In some embodiments, the first fusion protein and the second fusion protein are identical. In some embodiments, the first fusion protein and the second fusion protein of the (IL10M1)2-Fc fusion each comprise a polypeptide sequence of XENP25236 as depicted in  FIG. 26 . In some embodiments, the first fusion protein and the second fusion protein of the (IL10M1)2-Fc fusion each comprise a polypeptide sequence of XENP25237 as depicted in  FIG. 27 . 
     In another aspect, the present invention provides a heterodimeric Fc fusion protein comprising: (a) a fusion protein comprising a first protein domain, a second protein domain and a first Fc domain, wherein the first protein domain is attached to the first Fc domain, and wherein the second protein domain is covalently attached to the first protein domain; and (b) a second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first protein domain comprises a first IL10 monomer and the second protein domain comprises a second IL10 monomer, and wherein each of the first and second IL10 monomer comprises an insert peptide. The heterodimeric Fc fusion protein has an (IL10M1)2-heteroFc fusion format. 
     In some embodiments, the first protein domain is attached to the N-terminus of the first Fc domain. In some embodiments, the first protein domain is attached to the C-terminus of the first Fc domain. In some embodiments, the first protein domain is attached to the second protein domain using a first domain linker and/or the first protein domain is attached to the first Fc domain using a second domain linker. 
     In some embodiments, the modifications promoting heterodimerization of the first and the second Fc domains are a set of amino acid substitutions selected from the group consisting of L368D/K370S and S364K; L368D/K370S and S364K/E357L; L368D/K370S and S364K/E357Q; T411E/K360E/Q362E and D401K; L368E/K370S and S364K; K370S and S364K/E357Q and T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C), according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions comprising Q295E/N384D/Q418E/N421D, according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions consisting of G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. 
     In some embodiments, the first second Fc domain and/or the second Fc domain comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. 
     In some embodiments, the insert peptide comprises a domain linker engineered between helices D and E of an IL-10 monomer domain. 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:24 (IL10M1) as depicted in  FIG. 15D  and huIL10M1 variants as depicted in  FIGS. 75A-75B . 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain comprises a variant IL-10 domain. In some embodiments, the variant IL-10 domain comprising one or more amino acid modifications selected from the group consisting of N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, E151Q, C12A, C108A, Q38E/D41N, Q38E/Q42E, Q38E/N45D, Q38E/E142Q, Q38E/D144N, D41N/Q42E, D41N/N45D, D41N/E142Q, D41N/D144N, Q42E/N45D, Q42E/E142Q, Q42E/D144N, N45D/E142Q, N45D/D144N, E142Q/D144N, N21D/Q42E, N21D/N45D, N21D/E151Q, N21D/N45E, Q42E/E151Q, N45D/E151Q, N21D/Q42E/N45D, N21D/Q42E/E151Q, Q42E/N45D/E151Q, N21D/Q42E/N45E, N21D/Q42E/N45D/E151Q, F37C/M140C, Q38C/S141C, D41C/K138C, L47C/K138C, L48C/E142C, S51C/A120C, D55C/A120C, F56C/Y153C, C62A/C114A, A64C/S118C, M68C/V121C, V76C/A139C, L47Q, S118A, and A139Q. 
     In another aspect, the present invention provides a heterodimeric Fc fusion protein comprising: (a) a fusion protein comprising a first protein domain and a first Fc domain, wherein the first protein domain is covalently attached to the first Fc domain; and (b) a second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains and wherein the first protein domain comprises an IL-10 monomer that comprises an insert peptide. The heterodimeric Fc fusion has an (IL10M1)1-heteroFc fusion format. 
     In some embodiments, the first protein domain (e.g., an IL-10 monomer that comprises an insert peptide) is attached to the N-terminus of the first Fc domain. In some embodiments, the first protein domain is attached to the C-terminus of the first Fc domain. In some embodiments, the first protein domain is attached to the first Fc domain using a domain linker. 
     In some embodiments, the modifications promoting heterodimerization of the first and the second Fc domains are a set of amino acid substitutions selected from the group consisting of L368D/K370S and S364K; L368D/K370S and S364K/E357L; L368D/K370S and S364K/E357Q; T411E/K360E/Q362E and D401K; L368E/K370S and S364K; K370S and S364K/E357Q and T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C), according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions comprising Q295E/N384D/Q418E/N421D, according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions consisting of G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. 
     In some embodiments, the first Fc domain and/or second Fc domain comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. 
     1 In some embodiments, the insert peptide comprises a domain linker engineered between helices D and E of an IL-10 monomer domain. 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:24 (IL10M1) as depicted in  FIG. 15D  and huIL10M1 variants as depicted in  FIGS. 75A-75B . 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain comprises a variant IL-10 domain comprising one or more amino acid modifications selected from the group consisting of N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, E151Q, C12A, C108A, Q38E/D41N, Q38E/Q42E, Q38E/N45D, Q38E/E142Q, Q38E/D144N, D41N/Q42E, D41N/N45D, D41N/E142Q, D41N/D144N, Q42E/N45D, Q42E/E142Q, Q42E/D144N, N45D/E142Q, N45D/D144N, E142Q/D144N, N21D/Q42E, N21D/N45D, N21D/E151Q, N21D/N45E, Q42E/E151Q, N45D/E151Q, N21D/Q42E/N45D, N21D/Q42E/E151Q, Q42E/N45D/E151Q, N21D/Q42E/N45E, N21D/Q42E/N45D/E151Q, F37C/M140C, Q38C/S141C, D41C/K138C, L47C/K138C, L48C/E142C, S51C/A120C, D55C/A120C, F56C/Y153C, C62A/C114A, A64C/S118C, M68C/V121C, V76C/A139C, L47Q, S118A, and A139Q. 
     In another aspect, the present invention provides a heterodimeric Fc fusion protein comprising: (a) a first fusion protein comprising a first protein domain and a first Fc domain, wherein the first protein domain is covalently attached to the first Fc domain; and (b) a second fusion protein comprising a second protein domain and a second Fc domain, wherein the second protein domain is covalently attached to the second Fc domain; wherein the first protein domain comprises helices A-D of an IL-10 monomer domain and the second protein domain comprises helices E-F of an IL-10 monomer domain. The heterodimeric Fc fusion protein has a (splitIL10)1-heteroFc format. 
     In some embodiments, the first protein domain is covalently attached to the N-terminus of the first Fc domain and/or the second protein domain is covalently attached to the N-terminus of the second Fc domain. 
     In some embodiments, the first protein domain is covalently attached to the C-terminus of the first Fc domain and/or the second protein domain is covalently attached to the C-terminus of the second Fc domain. 
     In some embodiments, the first protein domain is covalently attached to the first Fc domain via a first domain linker and/or the second protein domain is covalently attached to the second Fc domain via a second domain linker. 
     In some embodiments, the first Fc domain and/or the second Fc domain comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. 
     In some embodiments, the first protein domain comprises a polypeptide sequence of SEQ ID NO:21 (hl-10(A-D)) as depicted in  FIG. 15A  or a polypeptide sequence having at least 90% (e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more) sequence identity to SEQ ID NO:21. In some embodiments, the second protein domain comprises a polypeptide sequence of SEQ ID NO:22 (hl-10(E-F)) as depicted in  FIG. 15B  or a polypeptide sequence having at least 90% (e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more) sequence identity to SEQ ID NO:22. 
     In some embodiments, the heterodimeric Fc fusion protein of the (splitIL10)1-heteroFc format comprises: (a) the first fusion protein having a polypeptide sequence of XENP25242 Chain 1 as depicted in  FIG. 30 , and (b) the second fusion protein having a polypeptide sequence of XENP25242 Chain 2 as depicted in  FIG. 30 . 
     In some embodiments, the heterodimeric Fc fusion protein of the (splitIL10)1-heteroFc format comprises: (a) the first fusion protein having a polypeptide sequence of XENP25243 Chain 1 as depicted in  FIG. 30 , and (b) the second fusion protein having a polypeptide sequence of XENP25243 Chain 2 as depicted in  FIG. 30 . 
     In some embodiments, the heterodimeric Fc fusion protein of the (splitIL10)1-heteroFc format comprises: (a) the first fusion protein having a polypeptide sequence of XENP25244 Chain 1 as depicted in  FIG. 30 , and (b) the second fusion protein having a polypeptide sequence of XENP25244 Chain 2 as depicted in  FIG. 30 . 
     Provided is a nucleic acid encoding any of the heterodimeric fusion protein described herein. Provided is a host cell comprising a nucleic acid encoding any of the heterodimeric fusion protein described herein. 
     In some embodiments, provided is a method of making a heterodimeric Fc fusion protein (e.g., a (splitIL10)1-heteroFc fusion protein) comprising culturing a host cell described under conditions whereby the heterodimeric Fc fusion protein is produced; and recovering the heterodimeric Fc fusion protein. 
     In another aspect, the present invention provides a heterodimeric Fc fusion protein comprising: (a) a first fusion protein comprising a first protein domain, a second protein domain, and a first Fc domain, wherein the first protein domain is covalently attached to the second protein domain, and the second protein domain is covalently attached to the first Fc domain; and (b) a second fusion protein comprising a third protein domain, a fourth protein domain, and a second Fc domain, wherein the third protein domain is covalently attached to the fourth protein domain, and the fourth protein domain is covalently attached to the second Fc domain; wherein the first protein domain and the second protein domain each comprises helices A-D of an IL-10 monomer domain, and wherein the third protein domain and the fourth protein domain each comprises helices E-F of an IL-10 monomer domain. The heterodimeric Fc fusion protein has a (splitIL10)2-heteroFc fusion format. 
     In some embodiments, the second protein is covalently attached to the N-terminus of the first Fc domain and/or the fourth protein domain is covalently attached to the N-terminus of the second Fc domain. 
     In some embodiments, the second protein is covalently attached to the C-terminus of the first Fc domain and/or the fourth protein domain is covalently attached to the C-terminus of the second Fc domain. 
     In some embodiments, the first protein domain is covalently attached to the second protein domain via a first domain linker and/or the third protein domain is covalently attached to the third protein domain via a second domain linker. 
     In some embodiments, the second protein domain is covalently attached to the first Fc domain via a third domain linker and/or the fourth protein domain is covalently attached to the second Fc domain via a fourth domain linker. 
     1 In some embodiments, the first and/or second Fc domains comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. In one embodiment, the first Fc domain comprises a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S. In one embodiment, the second Fc domain comprises a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S. In some embodiments, the first and second Fc domains each comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S. 
     In some embodiments, the first protein domain and/or the second protein domain comprises a polypeptide sequence of SEQ ID NO:21 (hlL-10(A-D)) as depicted in  FIG. 15A  or a polypeptide sequence having at least 90% (e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more) sequence identity to SEQ ID NO:21. In some embodiments, the third protein domain and/or the fourth protein domain comprises a polypeptide sequence of SEQ ID NO:22 (hlL-10(E-F)) as depicted in  FIG. 15B  or a polypeptide sequence having at least 90% (e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more) sequence identity to SEQ ID NO:22. 
     Provided is a nucleic acid encoding any of the heterodimeric fusion protein (e.g., (splitIL10)2-heteroFc fusion) described herein. Provided is a host cell comprising a nucleic acid encoding any of the heterodimeric fusion protein described herein. 
     In some embodiments, provided is a method of making a heterodimeric Fc fusion protein (e.g., a (splitIL10)2-heteroFc fusion protein) comprising culturing a host cell described under conditions whereby the heterodimeric Fc fusion protein is produced; and recovering the heterodimeric Fc fusion protein. 
     In another aspect, the present invention provides a heterodimeric Fc fusion protein comprising: (a) a first fusion protein comprising an antigen binding domain (ABD) and a first Fc domain, wherein the antigen binding domain is covalently attached to the N-terminus of the first Fc domain; and (b) a second fusion protein comprising a protein domain and a second Fc domain, wherein the protein domain is covalently attached to the N-terminus of the second Fc domain, and wherein the protein domain comprises a first IL-10 monomer domain. The heterodimeric Fc fusion protein has an anti-X×IL10-heteroFc fusion format. 
     In some embodiments, the heterodimeric Fc fusion protein further comprises a second IL-10 monomer domain non-covalently attached to the first IL-10 monomer domain. 
     In some embodiments, the antigen binding domain is attached to the first Fc domain using a first domain linker. In some embodiments, the first IL-10 monomer domain is attached to the second Fc domain using a second domain linker. 
     In some embodiments, the modifications promoting heterodimerization of the first and the second Fc domains are a set of amino acid substitutions selected from the group consisting of L368D/K370S and S364K; L368D/K370S and S364K/E357L; L368D/K370S and S364K/E357Q; T411E/K360E/Q362E and D401K; L368E/K370S and S364K; K370S and S364K/E357Q and T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C), according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions comprising Q295E/N384D/Q418E/N421D, according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions consisting of G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. 
     In some embodiments, the first Fc domain and/or the second Fc domain comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. 
     In some embodiments, the first and/or the second IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO:4 (human IL-10 (109L) mature form sequence), as depicted in  FIG. 1 . 
     In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain is a variant IL-10 monomer domain. 
     In some embodiments, the variant IL-10 monomer domain comprises an IL-10 monomer domain with one or more amino acid substitutions resulting in altered affinity for an IL-10 receptor, altered potency, altered potential for deamidation, altered potential for aspartic acid isomerization, altered potential for degradation-related PTMs, altered potential degradation sites, altered disulfide bridges, and/or altered potential N-glycosylation sites. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications at amino acid residues selected from the group consisting of N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, E151, and N160. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications selected from the group consisting of N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, E151Q, and N160del. 
     In some embodiments, the antigen binding domain (ABD) is selected from the group consisting of a PD-1 binding domain, a non-competing PD-1 binding domain, a TIGIT binding domain, a CD8 binding domain, and a NKG2D binding domain. 
     In some embodiments, the PD-1 binding domain is a humanized PD-1 ABD. In some embodiments, the humanized PD-1 ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting of: 1C11[PD-1]_H0L0, 1C11[P, D-1]_H3L3, 1C11[PD-1]_H3.240_L3.148, 1C11[PD-1]_H3.241_L3.148, 1C11[PD-1]_H3.234_L3.144, 1C11[PD-1]_H3.241_L3.92, 1C11[PD-1]_H3.303_L3.152, 1C11_H3.329_L3.220, 1C11_H3.328_L3.152, pembrolizumab variable heavy chain and variable light chain, nivolumab variable heavy chain and variable light chain, pidilizumab variable heavy chain and variable light chain, MK-3475 variable heavy chain and variable light chain, BAP049 Clone E variable heavy chain and variable light chain, BAP049 Clone B variable heavy chain and variable light chain, H7798N[PD-1] variable heavy chain and variable light chain, h1H3 Var 6[PD-1] variable heavy chain and variable light chain, APE2058[PD-1] variable heavy chain and variable light chain, H005-1[PD-1] variable heavy chain and variable light chain, 317-4B6[PD-1] variable heavy chain and variable light chain, 326-4A3[PD-1] variable heavy chain and variable light chain, hPD-1 mAb 7 (1.2)[PD-1] variable heavy chain and variable light chain, Clone 38[PD-1] variable heavy chain and variable light chain, Clone 39[PD-1] variable heavy chain and variable light chain, Clone 41[PD-1] variable heavy chain and variable light chain, Clone 48[PD-1] variable heavy chain and variable light chain, PD1-17[PD-1] variable heavy chain and variable light chain, PD1-28[PD-1] variable heavy chain and variable light chain, PD1-33[PD-1] variable heavy chain and variable light chain, PD1-35[PD-1] variable heavy chain and variable light chain, LOPD180 variable heavy chain and variable light chain, Ab948 variable heavy chain and variable light chain, humanized EH-12.2H7[PD-1] variable heavy chain and variable light chain, RG1H10 variable heavy chain and variable light chain, RG1H10-H2A-22-1S variable heavy chain and variable light chain, RG1H10-H2A-27-2S variable heavy chain and variable light chain, RG1H10-3C variable heavy chain and variable light chain, RG1H10-16C variable heavy chain and variable light chain, RG1H10-17C variable heavy chain and variable light chain, RG1H10-19C variable heavy chain and variable light chain, RG1H10-21C variable heavy chain and variable light chain, RG1H10-23C2 variable heavy chain and variable light chain, mAb7[PD-1], and PD1AB-6[PD-1] variable heavy chain and variable light chain, as depicted in  FIGS. 100A-100G . 
     In some embodiments, the non-competing PD-1 binding domain is a humanized non-competing PD1 ABD that does not bind the same epitope as nivolumab and/or pembrolizumab. In some embodiments, the humanized non-competing PD-1 ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting of: mAb A[PD-1]_H1_L1, mAb B[PD-1]_H1_L1, mAb C[PD-1]_H1_L1, mAb C[PD-1]_H1_L1.1, mAb C[PD-1]_H1_L1.3, mAb C[PD-1]_H1_L1.45, mAb C[PD-1]_H1_L1.117, mAb C[PD-1]_H1_L1.129, mAb C[PD-1]_H1_L1.135, mAb C[PD-1]_H1_L1.136, mAb C[PD-1]_H1_L1.140, mAb C[PD-1]_H1_L2, mAb C[PD-1]_H1.19_11, mAb C[PD-1]_H1.19_L1.1, mAb C[PD-1]_H1.19_L1.3, mAb C[PD-1]_H1.19_L1.45, mAb C[PD-1]_H1.19_L1.117, mAb C[PD-1]_H1.19_L1.129, mAb C[PD-1]_H1.19_L1.135, mAb C[PD-1]_H1.19_L1.136, mAb C[PD-1]_H1.19_L1.140, mAb C[PD-1]_H1.19_L2, mAb C[PD-1]_H1.48_11, mAb C[PD-1]_H1.48_L1.1, mAb C[PD-1]_H1.48_L1.3, mAb C[PD-1]_H1.48_L1.45, mAb C[PD-1]_H1.48_L1.117, mAb C[PD-1]_H1.48_L1.129, mAb C[PD-1]_H1.48_L1.135, mAb C[PD-1]_H1.48_L1.136, mAb C[PD-1]_H1.48_L1.140, mAb C[PD-1]_H1.48_L2, mAb C[PD-1]_H1.125_11, mAb C[PD-1]_H1.125_L1.1, mAb C[PD-1]_H1.125_L1.3, mAb C[PD-1]_H1.125_L1.45, mAb C[PD-1]_H1.125_L1.117, mAb C[PD-1]_H1.125_L1.129, mAb C[PD-1]_H1.125_L1.135, mAb C[PD-1]_H1.125_L1.136, mAb C[PD-1]_H1.125_L1.140, mAb C[PD-1]_H1.125_L2, mAb C[PD-1]_H1.130_11, mAb C[PD-1]_H1.130_L1.1, mAb C[PD-1]_H1.130_L1.3, mAb C[PD-1]_H1.130_L1.45, mAb C[PD-1]_H1.130_L1.117, mAb C[PD-1]_H1.130_L1.129, mAb C[PD-1]_H1.130_L1.135, mAb C[PD-1]_H1.130_L1.136, mAb C[PD-1]_H1.130_L1.140, mAb C[PD-1]_H1.130_L2, mAb C[PD-1]_H1.132_11, mAb C[PD-1]_H1.132_L1.1, mAb C[PD-1]_H1.132_L1.3, mAb C[PD-1]_H1.132_L1.45, mAb C[PD-1]_H1.132_L1.117, mAb C[PD-1]_H1.132_L1.129, mAb C[PD-1]_H1.132_L1.135, mAb C[PD-1]_H1.132_L1.136, mAb C[PD-1]_H1.132_L1.140, mAb C[PD-1]_H1.132_L2, mAb C[PD-1]_H1.169_11, mAb C[PD-1]_H1.169_L1.1, mAb C[PD-1]_H1.169_L1.3, mAb C[PD-1]_H1.169_L1.45, mAb C[PD-1]_H1.169_L1.117, mAb C[PD-1]_H1.169_L1.129, mAb C[PD-1]_H1.169_L1.135, mAb C[PD-1]_H1.169_L1.136, mAb C[PD-1]_H1.169_L1.140, mAb C[PD-1]_H1.169_L2, mAb C[PD-1]_H1.175_11, mAb C[PD-1]_H1.175_L1.1, mAb C[PD-1]_H1.175_L1.3, mAb C[PD-1]_H1.175_L1.45, mAb C[PD-1]_H1.175_L1.117, mAb C[PD-1]_H1.175_L1.129, mAb C[PD-1]_H1.175_L1.135, mAb C[PD-1]_H1.175_L1.136, mAb C[PD-1]_H1.175_L1.140, mAb C[PD-1]_H1.175_L2, mAb C[PD-1]_H2_L1, mAb C[PD-1]_H2_L1.1, mAb C[PD-1]_H2_L1.3, mAb C[PD-1]_H2_L1.45, mAb C[PD-1]_H2_L1.117, mAb C[PD-1]_H2_L1.129, mAb C[PD-1]_H2_L1.135, mAb C[PD-1]_H2_L1.136, mAb C[PD-1]_H2_L1.140, and mAb C[PD-1]_H2_L2, as depicted in  FIGS. 104A-104B . 
     In some embodiments, the CD8 binding domain is a humanized CD8 ABD. In some embodiments, the humanized CD8 ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting OKT8_H2L1 and 1C11B3_H1L1, as depicted in  FIG. 92 . 
     In some embodiments, the NKG2D binding domain is a humanized NKG2D ABD. In some embodiments, the humanized NKG2D ABD comprises a variable heavy chain and variable light chain pair selected from a group consisting MS[NKG2D] H0_L0, 1D7B4[NKG2D]_H1_L1, KYK-1.0[NKG2D]_H1_L1, KYK-2.0[NKG2D]_H0_L0, 11B2D10[NKG2D]_H0_L0, 6E5A7[NKG2D]_H0_L0, 6H7E7[NKG2D]_H0_L0, mAb E[NKG2D]_H1_L1, 16F31[NKG2D]_H1_L1, mAb D[NKG2D]_H1_L1, 1 D7B4[NKG2D]_H1_L1, mAb A[NKG2D]_H1_L1, mAb A[NKG2D]_H2_L1, mAb A[NKG2D]_H1_L2, mAb A[NKG2D]_H2_L2, mAb B[NKG2D]_H1_L1, mAb B[NKG2D]_H1_L1.1, mAb B[NKG2D]_H1_L2, mAb B[NKG2D]_H2_L1, mAb B[NKG2D]_H2_L1.1, mAb B[NKG2D]_H2_L2, mAb B[NKG2D]_H3_L1, mAb B[NKG2D]_H3_L1.1, mAb B[NKG2D]_H3_L2, mAb C[NKG2D]_H1_L1, mAb C[NKG2D]_H2_L1, mAb C[NKG2D]_H1_L2, and mAb C[NKG2D]_H2_L2, as depicted in  FIGS. 93A-93C . 
     Provided is a nucleic acid encoding any of the heterodimeric fusion protein described herein of the anti-X×IL-10-heteroFc fusion format. Provided is a host cell comprising a nucleic acid encoding any of the heterodimeric fusion protein described herein. 
     In some embodiments, provided is a method of making a heterodimeric Fc fusion protein (e.g., an anti-X×IL-10-heteroFc fusion protein) comprising culturing a host cell described under conditions whereby the heterodimeric Fc fusion protein is produced; and recovering the heterodimeric Fc fusion protein. 
     In some embodiments, provided herein is a method of purifying a heterodimeric Fc fusion protein described herein of the anti-X×IL-10-heteroFc fusion format. The method comprises: (a) providing a composition comprising the heterodimeric Fc fusion protein; (b) loading the composition onto an ion exchange column; and (c) collecting a fraction containing the heterodimeric Fc fusion protein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts the sequences for human IL-10 (both the IL-10(109H) and IL-10(109L) sequences) and its receptors. 
         FIG. 2  depicts the sequences for mouse IL-10 and its receptors to facilitate investigation of IL-10 fusion proteins of the invention in preclinical studies. 
         FIG. 3  depicts the sequences for cynomolgus IL-10 and its receptors to facilitate investigation of IL-10 fusion proteins of the invention in preclinical studies. 
         FIG. 4  depicts the sequences for viral IL-10 homolog. 
         FIG. 5A-5E  depict useful pairs of Fc heterodimerization variant sets (including skew and pI variants). Variants without a corresponding “monomer 2” are pI variants which can be used alone on either monomer. 
         FIG. 6  depict a list of isosteric variant antibody constant regions and their respective substitutions. pI_(−) indicates lower pI variants, while pI_(+) indicates higher pI variants. These can be optionally and independently combined with other heterodimerization variants of the inventions (and other variant types as well, as outlined herein.) 
         FIG. 7  depict useful ablation variants that ablate FcγR binding (sometimes referred to as “knock outs” or “KO” variants). Generally, ablation variants are found on both monomers, although in some cases they may be on only one monomer. 
         FIG. 8  shows a particularly useful embodiment of “non-cytokine” components of the IL-10 fusions of the invention. 
         FIG. 9  shows particularly useful embodiments of “non-cytokine”/“non-Fv” components of the invention. 
         FIG. 10  shows the sequences of several useful homodimeric IL-10 fusion backbones based on human IgG1, without the cytokine sequences. Homodimeric Fc backbone 1 is based on human IgG1 (356E/358M allotype), and includes the E233P/L234V/L235A/G236del/S267K ablation variants and C220S. Homodimeric Fc backbone 2 is based on human IGG1 (356D/358L allotype), and includes the E233P/L234V/L235A/G236del/S267K ablation variants and C220S. Homodimeric Fc backbone 3 is based on human IgG4, and the S228P (according to EU numbering; S241P in Kabat) variant that ablates Fab arm exchange (as is known in the art). Homodimeric Fc backbone 4 is based on human IgG2, and includes the S267K ablation variant. Alternative formats for homodimeric backbone 4 can include C219S and/or C220S. These sequences can be used with any of the IL-10 fusions of the inventions utilizing a homodimeric Fc region. These sequences can also be used with formats of the targeted IL-10 fusions of the invention utilizing a homodimeric Fc region. In targeted IL-10 fusion formats which include a variable heavy domain covalently linked to the Fc, the variable heavy domain may be covalently linked to the Fc domain by a corresponding CH1 domain and partial hinge region, illustrative sequences for which are depicted in  FIG. 12 , and may exclude the C220S and/or C219S substitutions. 
         FIG. 11A-11C  show the sequences of several useful heterodimeric IL-10 fusion backbones based on human IgG1, without the cytokine sequences. While these backbones find use in the IL-10 fusions of the invention, they also find use in formats of the targeted IL-10 fusions of the invention. Heterodimeric Fc backbone 1 is based on human IgG1 (356E/358M allotype), and includes the L368D/K370S skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the S364K/E357Q skew variants on a second heterodimeric Fc chain, and the E233P/L234V/L235A/G236del/S267K ablation variants and C220S on both chains. Heterodimeric Fc backbone 2 is based on human IgG1 (356E/358M allotype), and includes the L368D/K370S skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the S364K skew variant on a second heterodimeric Fc chain, and the E233P/L234V/L235A/G236del/S267K ablation variants and C220S on both chains. Heterodimeric Fc backbone 3 is based on human IgG1 (356E/358M allotype), and includes the L368E/K370S skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the S364K skew variant on a second heterodimeric Fc chain, and the E233P/L234V/L235A/G236del/S267K ablation variants and C220S on both chains. Heterodimeric Fc backbone 4 is based on human IgG1 (356E/358M allotype), and includes the K360E/Q362E/T411E skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the D401K skew variant on a second heterodimeric Fc chain, and the E233P/L234V/L235A/G236del/S267K ablation variants and C220S on both chains. Heterodimeric Fc backbone 5 is based on human IgG1 (356D/358L allotype), and includes the L368D/K370S skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the S364K/E357Q skew variants on a second heterodimeric Fc chain, and the E233P/L234V/L235A/G236del/S267K ablation variants and C220S on both chains. Heterodimeric Fc backbone 6 is based on human IgG1 (356E/358M allotype), and includes the L368D/K370S skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the S364K/E357Q skew variants on a second heterodimeric Fc chain, and the E233P/L234V/L235A/G236del/S267K ablation variants, N297A variant that removes glycosylation, and C220S on both chains. Heterodimeric Fc backbone 7 is based on human IgG1 (356E/358M allotype), and includes the L368D/K370S skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the S364K/E357Q skew variants on a second heterodimeric Fc chain, and the E233P/L234V/L235A/G236del/S267K ablation variants, N297S variant that removes glycosylation, and C220S on both chains. Heterodimeric Fc backbone 8 is based on human IgG4, and includes the L368D/K370S skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the S364K/E357Q skew variants on a second heterodimeric Fc chain, and the S228P (according to EU numbering, S241P in Kabat) variant that ablates Fab arm exchange (as is known in the art) on both chains. Heterodimeric Fc backbone 9 is based on human IgG2, and includes the L368D/K370S skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the S364K/E357Q skew variants on a second heterodimeric Fc chain. Heterodimeric Fc backbone 10 is based on human IgG2, and includes the L368D/K370S skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the S364K/E357Q skew variants on a second heterodimeric Fc chain, and the S267K ablation variant on both chains. Alternative formats for heterodimeric Fc backbones 9 and 10 can include C220S and/or C219S (in the case of a backbone based on IgG2). Heterodimeric Fc backbone 11 is based on human IgG1 (356E/358M allotype), and includes the L368D/K370S skew variants and the Q295E/N384D/Q418E/N421D pI variants on a first heterodimeric Fc chain, the S364K/E357Q skew variants on a second heterodimeric Fc chain, and the E233P/L234V/L235A/G236del/S267K ablation variants, M428L/N434S Xtend variants, and C220S on both chains. Heterodimeric Fc backbone 12 is based on human IgG1 (356E/358M allotype), and includes the L368D/K370S skew variants on a first heterodimeric Fc chain, the S364K/E357Q skew variants and P217R/P229R/N276K pI variants on a second heterodimeric Fc chain, and the E233P/L234V/L235A/G236del/S267K ablation variants and C220S on both chains. 
       As will be appreciated by those in the art and outlined below, these sequences can be used with any IL-10 fusion formats requiring a heterodimeric Fc region. It should be noted that for C-terminal Fc fusion formats (e.g. heteroFc-scIL10), the backbones may further comprise deletion of K447 on one or both chains. 
       These sequences can also be used with any of the targeted IL-10 fusions of the invention requiring a heterodimeric Fc region. In targeted IL-10 fusion formats which include a variable heavy domain covalently linked to the Fc, the variable heavy domain may be covalently linked to the Fc domain by a corresponding CH1 domain and partial hinge region, illustrative sequences for which are depicted in  FIG. 12 , and may exclude the C220S and/or C219S substitutions. 
       Included within each of these backbones are sequences that are 90, 95, 98 and 99% identical (as defined herein) to the recited sequences, and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions (as compared to the “parent” of the Figure, which, as will be appreciated by those in the art, already contain a number of amino acid modifications as compared to the parental human IgG1 (or IgG2 or IgG4, depending on the backbone). That is, the recited backbones may contain additional amino acid modifications (generally amino acid substitutions) in addition or as an alternative to the skew, pI and ablation variants contained within the backbones of this Figure. 
         FIG. 12  depicts illustrative CH1 and partial hinge regions which may find use in covalently linking a variable domain to the backbones as depicted in  FIGS. 10 and 11  in the context of particular formats of targeted IL-10 fusions. 
         FIG. 13  depicts the “non-Fv” backbone of cognate light chains (i.e. constant light chain) which find use in the bottle-opener and central-scFv bispecific antibodies of the invention. 
         FIG. 14A-14F  depicts cartoon schematics for IL-10 components and configurations that find use in the IL-10 fusion proteins of the invention.  FIG. 14A  depicts the hIL-10(A-D) domain comprising residues 1-116 of the mature form IL-10.  FIG. 14B  depicts the hIL-10(E-F) domain comprising residues 117-160 of the mature form IL-10.  FIG. 14C  depicts the biologically active IL-10 homodimer formed by domain swapping between hIL-10(A-D) of a first IL-10 monomer and hIL-10(E-F) of a second IL-10 monomer.  FIG. 14D  depicts the single-chain IL-10 complex or “scIL-10” comprising a first IL-10 monomer covalently attached to a second IL-10 monomer, optionally via a linker.  FIG. 14E  depicts the monomeric IL-10 or “IL10M1” described by Josephson et al. (2000), which is generated by engineering a domain linker between hIL-10(A-D) and hIL-10(E-F) domains in an IL-10 monomer.  FIG. 14F  depicts the split IL-10 which comprises an hIL-10(A-D) domain non-covalently attached to an hIL-10(E-F) domain. 
         FIG. 15A-15D  depicts the sequences for IL-10 components and configurations that find use in the IL-10 fusion proteins of the invention.  FIG. 15A  depicts the hIL-10(A-D) domain comprising residues 1-116 of the mature form IL-10.  FIG. 15B  depicts the hIL-10(E-F) domain comprising residues 117-160 of the mature form IL-10.  FIG. 15C  depicts the single-chain IL-10 complex or “scIL-10” comprising a first IL-10 monomer covalently attached to a second IL-10 monomer, although it should be noted that the scIL-10 can optionally include a linker, as is known in the art, between the first and the second IL-10 monomer.  FIG. 15D  depicts the monomeric IL-10 or “IL10M1” described by Josephson et al. (2000), which is generated by engineering a domain linker between hIL-10(A-D) and hIL-10(E-F) domains in an IL-10 monomer, although as will be appreciated by those in the art, the linker can be replaced by other linkers as are known in the art. It should be noted that while the IL-10 sequence depicted herein comprise 109H, the sequences can also comprise 109L, as well as sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 16A-16D  depicts illustrative formats for IL-10 fusions in the IL10-Fc category. The N-terminal IL-10 Fc fusion or “(IL10) 2 -Fc” ( FIG. 16A ) format comprises two identical monomers, each monomer comprising an IL-10 monomer covalently attached to the N-terminus of a homodimeric Fc chain, optionally via a domain linker (e.g., XENP24628). The C-terminal IL-10 Fc fusion or “Fc-(IL10) 2 ” ( FIG. 16B ) format comprises two identical monomers, each monomer comprising an IL-10 monomer covalently attached to the C-terminus of a homodimeric Fc chain, optionally via a domain linker (e.g., XENP24632). The “(IL10-NC-IL10)-heteroFc” ( FIG. 16C ) format comprises a first monomer comprising a first IL-10 monomer covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a domain linker) and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”, while a second IL-10 monomer is transfected separately so that a non-covalent IL-10 dimer is formed (e.g., XENP25955). The “heteroFc-(IL10-NC-IL10)” ( FIG. 16D ) format comprises a first monomer comprising a first IL-10 monomer covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a domain linker) and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”, while a second IL-10 monomer is transfected separately so that a domain-swapped IL-10 dimer is formed. 
         FIG. 17  depicts the sequences for illustrative IL-10 fusions of the IL10-Fc category in the (IL10) 2 -Fc format (e.g., XENP24628, XENP246289, XENP24630, and XENP24631). IL-10 sequences are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the IL-10 fusions can utilize an IL-10 sequence comprising 109H, as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 18  depicts the sequences for illustrative IL-10 fusions of the IL10-Fc category in the Fc-(IL10) 2  format (e.g., XENP24632, XENP24633, and XENP24634). IL-10 sequences are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the IL-10 fusion can utilize an IL-10 sequence comprising 109H, as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 19  depicts the sequences for an illustrative IL-10 fusion of the IL10-Fc category in the (IL10-NC-IL10)-heteroFc format (e.g., XENP25955). IL-10 sequences are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the IL-10 fusion can utilize an IL-10 sequence comprising 109H, as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 20A - FIG. 20B  depict illustrative formats for IL-10 fusions in the scIL10-Fc category, utilizing the single-chain IL-10 (“scIL10”) complex as depicted in  FIG. 15 . The N-terminal single-chain IL-10 Fc fusion or “scIL10-heteroFc” ( FIG. 20A ) format comprises a first monomer comprising a scIL-10 covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a domain linker) and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc” (e.g., XENP25238). The C-terminal single-chain IL-10 Fc fusion or “heteroFc-scIL10” ( FIG. 20B ) format comprises a first monomer comprising a scIL-10 covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a domain linker) and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc” (e.g., XENP28740). The scIL-10 complex used in formats of this category comprise a first IL-10 monomer covalently attached to a second IL-10 monomer, optionally via a domain linker. 
         FIG. 21A - FIG. 21C  depict the sequences for illustrative IL-10 fusions of the scIL10-Fc category in the scIL10-heteroFc format (e.g., XENP25238, XENP25239, XENP25240, XENP25241, XENP25880, and XENP28295). IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 22  depicts the sequences for an illustrative IL-10 fusions of the scIL10-Fc category in the heteroFc-scIL10 format (e.g., XENP28740). IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 23A - FIG. 23F  depict illustrative formats for IL-10 fusions in the IL10M1-Fc category, utilizing the monomeric IL-10 (IL10M1) described by Josephson et al. (2000) as depicted in  FIGS. 14 and 15 . The N-terminal bivalent IL10M1 Fc fusion or “(IL10M1)2-Fc” ( FIG. 23A ) format comprises two identical monomers, each monomer comprising an IL10M1 covalently attached to the N-terminus of a homodimeric Fc chain, optionally via a domain linker (e.g., XENP25326). The C-terminal bivalent IL10M1 Fc fusion or “Fc-(IL10M1) 2 ” ( FIG. 23B ) format comprises two identical monomers, each monomer comprising an IL10M1 covalently attached to the C-terminus of a homodimeric Fc chain, optionally via a domain linker (e.g., XENP25327). The one-arm N-terminal bivalent IL10M1 Fc fusion or “(IL10M1) 2 -heteroFc” ( FIG. 23C ) format comprises a first monomer comprising a first IL10M1 covalently attached to a second IL10M1 (optionally via a linker) further covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. The one-arm C-terminal bivalent IL10M1 Fc fusion or “heteroFc-(IL10M1) 2 ” ( FIG. 23D ) format comprises a first monomer comprising a first IL10M1 covalently attached to a second IL10M1 (optionally via a linker) further covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. The N-terminal monovalent IL10M1 fusion or “(IL10M1) 1 -heteroFc” ( FIG. 23E ) format comprises an IL10M1 covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. The C-terminal monovalent IL10M1 fusion or “heteroFc-(IL10M1) 1 ” ( FIG. 23F ) format comprises an IL10M1 covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. The IL10M1 used in formats of this category is generated by engineering a domain linker between helices D and E of an IL-10 monomer. 
         FIG. 24  depicts the sequences for an illustrative IL-10 fusion of the IL10M1-Fc category in the (IL10M1) 1 -heteroFc format (e.g., XENP14246). IL-10M1 sequences are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL10M1, linkers, and Fc regions. It should be noted that while the IL10M1 sequence depicted herein comprise 109H (numbered according to mature form IL-10 monomer without an internal linker), the IL-10 fusion can utilize an IL10M1 sequence comprising 109L, as well as IL10M1 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 25  depicts the sequences for an illustrative IL-10 fusion of the IL10M1-Fc category in the heteroFc-(IL10M1) 1  format (e.g., XENP14247). IL-10M1 sequences are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL10M1, linkers, and Fc regions. It should be noted that while the IL10M1 sequence depicted herein comprise 109H (numbered according to mature form IL-10 monomer without an internal linker), the IL-10 fusion can utilize an IL10M1 sequence comprising 109L, as well as IL10M1 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 26  depicts the sequences for an illustrative IL-10 fusion of the IL10M1-Fc category in the (IL10M1) 2 -Fc format (e.g., XENP25236). IL-10M1 sequences are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL10M1, linkers, and Fc regions. It should be noted that while the IL10M1 sequence depicted herein comprise 109H (numbered according to mature form IL-10 monomer without an internal linker), the IL-10 fusion can utilize an IL10M1 sequence comprising 109L, as well as IL10M1 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 27  depicts the sequences for an illustrative IL-10 fusion of the IL10M1-Fc category in the Fc-(IL10M1) 2  format (e.g., XENP25237). IL-10M1 sequences are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL10M1, linkers, and Fc regions. It should be noted that while the IL10M1 sequence depicted herein comprise 109H (numbered according to mature form IL-10 monomer without an internal linker), the IL-10 fusion can utilize an IL10M1 sequence comprising 109L, as well as IL10M1 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 28  depicts the sequences for an illustrative IL-10 fusion of the IL10M1-Fc category in the (IL10M1) 2 -heteroFc format (e.g., XENP26887). IL-10M1 sequences are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL10M1, linkers, and Fc regions. It should be noted that while the IL10M1 sequence depicted herein comprise 109H (numbered according to mature form IL-10 monomer without an internal linker), the IL-10 fusion can utilize an IL10M1 sequence comprising 109L, as well as IL10M1 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 29A - FIG. 29D  depicts illustrative formats for IL-10 fusions in the splitIL10-Fc category, utilizing hIL-10(A-D) and hIL-10(E-F) domains as depicted in  FIGS. 14A-14F and 15A-15D . The N-terminal monovalent splitIL-10 Fc fusion or “(splitIL10) 1 -heteroFc” ( FIG. 29A ) comprises a first monomer comprising a hIL-10(A-D) domain covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a linker) and a second monomer comprising a hIL-10(E-F) domain covalently attached the N-terminus of a complementary second heterodimeric Fc chain (optionally via a linker) (e.g., XENP25242). The C-terminal monovalent splitIL-10 Fc fusion or “heteroFc-(splitIL10) 1 ” ( FIG. 29B ) comprises a first monomer comprising a hIL-10(A-D) domain covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a linker) and a second monomer comprising a hIL-10(E-F) domain covalently attached the C-terminus of a complementary second heterodimeric Fc chain (optionally via a linker). The N-terminal bivalent splitIL-10 Fc fusion or “(splitIL10) 2 -heteroFc” ( FIG. 29C ) comprises a first monomer comprising a first hIL-10(A-D) domain covalently attached to a second hIL-10(A-D) domain (optionally via a linker) further covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a linker) and a second monomer comprising a first hIL-10(E-F) domain covalently attached to a second hIL-10(E-F) domain (optionally via a domain linker) further covalently attached to the N-terminus of a complementary second heterodimeric Fc chain (optionally via a linker). The C-terminal bivalent splitIL-10 Fc fusion or “heteroFc-(splitIL10) 2 ” ( FIG. 29D ) comprises a first monomer comprising a first hIL-10(A-D) domain covalently attached to a second hIL-10(A-D) domain (optionally via a linker) further covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a linker) and a second monomer comprising a first hIL-10(E-F) domain covalently attached to a second hIL-10(E-F) domain (optionally via a domain linker) further covalently attached to the C-terminus of a complementary second heterodimeric Fc chain (optionally via a linker). 
         FIG. 30  depicts the sequences for illustrative IL-10 fusion of the splitIL10-Fc category in the splitIL10-heteroFc format (e.g., XENP25242, XENP25243, and XENP25244). Sequences of IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 components, linkers, and Fc regions. It should be noted that while the hIL-10(A-D) sequence depicted herein comprise 109L (numbered according to mature form IL-10 monomer), the IL-10 fusion can utilize an hIL-10(A-D) sequence comprising 109H. Further, the IL-10 fusion can utilize hIL-10(A-D) and/or hIL-10(E-F) sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 31  depicts the sequences for illustrative IL-10 fusion of the splitIL10-Fc category in the heteroFc-splitIL10 format (e.g., XENP25879). Sequences of IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 components, linkers, and Fc regions. It should be noted that while the hIL-10(A-D) sequence depicted herein comprise 109L (numbered according to mature form IL-10 monomer), the IL-10 fusion can utilize an hIL-10(A-D) sequence comprising 109H. Further, the IL-10 fusion can utilize hIL-10(A-D) and/or hIL-10(E-F) sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 32A - FIG. 32C  depict A) chromatogram illustrating purification part 2 of XENP25880 (cation exchange chromatography following protein A chromatography), and the purity and homogeneity of peak B isolated from cation exchange separation as depicted in  FIG. 32A  in comparison to peak BC as determined by B) analytical size-exclusion chromatography with multi-angle light scattering (aSEC-MALS) and C) analytical cation exchange chromatography (aCIEX).  FIG. 32B  also depicts the molecular weight of protein species in peaks as determined by multi-angle light scattering. 
         FIG. 33A - FIG. 33E  depict induction of STAT3 phosphorylation by IL-10 fusion proteins in the IL10-Fc format (XENP24628), scIL10-Fc format (XENP25880), IL10M1-Fc format (XENP25236), and splitIL10-Fc format (XENP25242) as well as recombinant IL-10 control on A) CD4 + CD25 + CD45RA −  T cells, B) CD4 + CD25 int CD45RA +  T cells, C) CD8 + CD25 + CD45RA −  T cells, D) CD8 + CD25 int CD45RA +  T cells, and E) Tregs. The data show that IL-10 fusions in the scIL0-Fc format (XENP25880) induced STAT3 phosphorylation on various lymphocyte populations. 
         FIG. 34A - FIG. 34E  depict induction of STAT3 phosphorylation by IL-10 fusion proteins with N-terminal IL-10 (XENP25981) and C-terminal IL-10 (XENP28741) as well as recombinant IL-10 control on A) CD4 + CD45RA −  T cells, B) CD4 + CD45RA +  T cells, C) CD8 + CD45RA −  T cells, D) CD8 + CD45RA +  T cells, and E) Tregs. The data show that C-terminal Fc fusion XENP28741 induced STAT3 phosphorylation more potently than N-terminal Fc fusion XENP25981. 
         FIG. 35A - FIG. 35D  depict sequences for illustrative IL-10 monomer variants designed with the aim to reduce their affinity for the IL-10 receptor complex and/or to reduce their potency. It should be noted that these IL-10 variant sequences are based on the IL-10(109L) sequence, although they can be based on the IL-10(109H) sequence. Each of the substitutions herein can be used alone or in combination with any other substitutions depicted herein. Additionally, as will be clear to those skilled in the art, while the substitutions herein are depicted in the context of an IL-10 monomer, each of the substitutions can be used alone or in combination in the context of IL-10 domains (e.g. hIL-10(A-D) and hIL-10(E-F)), scIL-10, and IL10M1. Further, each of the substitutions depicted in this Figure can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 36A - FIG. 36D  depict sequences for illustrative IL10M1 variants designed with the aim to reduce their affinity for the IL-10 receptor complex and/or to reduce their potency. It should be noted that these IL-10 variant sequences are based on the IL-10(109H) sequence, although they can be based on the IL-10(109L) sequence. Each of the substitutions depicted in this Figure can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 37A - FIG. 37E  depict the sequences illustrative IL-10 fusions of the IL10M1-Fc category in the (IL10M1) 1 -heteroFc format comprising IL10M1 variants engineered with the aim to reduce affinity and potency. IL-10M1 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL10M1, linkers, and Fc regions. It should be noted that while the IL10M1 sequence depicted herein comprise 109H (numbered according to mature form IL-10 monomer without an internal linker), the IL-10 fusion can utilize an IL10M1 sequence comprising 109L, as well as IL10M1 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 38  depicts the dissociation constant (K D ), association rate (k a ), and dissociation rate (k d ) of (IL10M1) 1 -heteroFc fusions comprising affinity-engineered IL10M1 variants binding to human IL-10R1 as determined by Octet, a BLI-based method. Bivalent human IL-10-Fc were captured on AR2G biosensors and dipped into multiple concentrations of the indicated test articles. * indicates poor fits from biphasic sensorgrams. The data show that we engineered IL-10 variants with a range of affinities for IL-10R1. 
         FIG. 39A - FIG. 39G  depict sequences for illustrative scIL-10 variants designed with the aim to reduce their affinity for the IL-10 receptor complex and/or to reduce their potency. It should be noted that these IL-10 variant sequences are based on the IL-10(109L) sequence, although they can also be based on the IL-10(109H) sequence. Each of the substitutions depicted in this Figure can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or enhance stability. It should also be noted that these scIL-10 variants can optionally include a linker between each IL-10 sequence, although numbering of the substitutions would be based on the full-length scIL-10 sequence as depicted in  FIG. 15C   
         FIG. 40A - FIG. 40N  depict the sequences illustrative IL-10 fusions of the scIL10-Fc category in the scIL10-heteroFc format comprising scIL-10 variants engineered with the aim to reduce affinity and potency. IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 41A - FIG. 41F  depict the sequences illustrative IL-10 fusions of the scIL10-Fc category in the heteroFc-scIL10 format comprising scIL-10 variants engineered with the aim to reduce affinity and potency. IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 42A - FIG. 42E  depicts induction of STAT3 phosphorylation by scIL10-heteroFc fusions comprising affinity-engineered scIL-10 variants on A) CD4 + CD45RA −  T cells, B) CD4 + CD45RA +  T cells, C) CD8 + CD45RA −  T cells, D) CD8 + CD45RA +  T cells, and E) Tregs. The data illustrates that we engineered IL-10 fusions with a wide range of potencies (as indicated by induction of STAT3 phosphorylation). 
         FIG. 43A - FIG. 43C  depict the potentiation of A) IFNγ secretion, B) proliferation (as indicated by percentage cells expressing Ki67), and C) activation (as indicated by CD25 expression) of purified CD8 +  T cells by scIL10-heteroFc fusions comprising affinity-engineered scIL-10 variants. The data show that IL-10 fusion proteins of the invention potentiate IFNγ secretion by CD8 +  T cells, activation of CD8 +  T cells, and proliferation of CD8 +  T cells. 
         FIG. 44A - FIG. 44C  depict the potentiation of A) IFNγ secretion, B) proliferation (as indicated by percentage cells expressing Ki67), and C) activation (as indicated by CD25 expression) of purified CD8 +  T cells by scIL10-heteroFc fusions comprising additional affinity-engineered scIL-10 variants. The data show that IL-10 fusion proteins of the invention potentiate IFNγ secretion by CD8 +  T cells, activation of CD8 +  T cells, and proliferation of CD8 +  T cells. 
         FIG. 45A - FIG. 45C  depict the correlation between the EC50 for A) IFNγ secretion, B) proliferation, and C) activation of CD8 +  T cells and EC50 for induction of STAT3 phosphorylation by scIL10-heteroFc fusions comprising additional affinity-engineered scIL-10 variants. The data show that the EC50 for induction of STAT3 phosphorylation correlated well with the EC50 for potentiation of IFNγ secretion, activation of CD8 +  T cells, and proliferation of CD8 +  T cells. 
         FIG. 46A - FIG. 46C  depict A) chromatogram illustrating purification part 2 of XENP25238 (cation exchange chromatography following protein A chromatography), and the purity and homogeneity of peak B isolated from cation exchange separation as depicted in  FIG. 46A  in comparison to peak BC as determined by B) analytical size-exclusion chromatography with multi-angle light scattering (aSEC-MALS) and C) analytical cation exchange chromatography (aCIEX).  FIG. 46B  also depicts the molecular weight of protein species in peaks as determined by multi-angle light scattering. 
         FIG. 47A - FIG. 47E  depicts induction of STAT3 phosphorylation by scIL10-heteroFc fusion proteins with the scIL-10 complex on the heterodimeric Fc chain with a lower pI (XENP25238) and on the heterodimeric chain with a higher pI (XENP25880) on A) CD4 + CD25 + CD45RA −  T cells, B) CD4 + CD25 int CD45RA +  T cells, C) CD8 + CD25 + CD45RA −  T cells, D) CD8 + CD25 int CD45RA +  T cells, and E) Tregs. 
         FIG. 48  depicts illustrative sequences for single-chain IL-10 complexes (scIL-10) comprising domain linkers between the first IL-10 monomer and the second IL-10 monomer. IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomers and linker. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the full-length scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 49A - FIG. 49B  depicts the sequences for illustrative IL-10 fusions of the scIL10-Fc category in the scIL10-heteroFc format comprising scIL-10 complexes having domain linkers between the first and the second IL-10 monomer. IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10). Additionally, while the IL-10 sequences depicted herein are wild-type, the IL-10 fusions can utilize IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 50A - FIG. 50E  depict induction of STAT3 phosphorylation by scIL10-heteroFc fusion proteins with no linker (XENP25238), a G 4 S linker (SEQ ID NO: 31) (XENP25239), a (G 4 S) 2  linker (SEQ ID NO: 32) (XENP25240), and a (G 4 S) 3  linker (SEQ ID NO: 33) (XENP25241) engineered within the scIL-10 complex on A) CD4 + CD25 + CD45RA −  T cells, B) CD4 + CD25 int CD45RA +  T cells, C) CD8 + CD25 + CD45RA −  T cells, D) CD8 + CD25 int CD45RA +  T cells, and E) Tregs. 
         FIG. 51A - FIG. 51B  depict the analytical cation exchange separation profile for Protein A purified (purification part 1) samples of A) XENP25880 and B) XENP25981 from production batch 20180213. 
         FIG. 52  depicts total protein yield (all protein as purified by Protein A in purification part 1; mg/L), percent homodimer and percent heterodimer (as determined by analytical cation exchange separation of Protein A purified material), and homodimer and heterodimer yield (calculated based on total protein yield and percentage homodimer or heterodimer) for various production batches of XENP25880 and XENP25981. The data show that production of XENP25981 generally resulted in greater yield of the scIL10-heteroFc fusion over empty-Fc homodimer suggesting that the N45D substitution enhanced heterodimer yield. 
         FIG. 53  depicts the sequences for XENP25986 and XENP25993, illustrative variant scIL10-heteroFc fusions having N45D and N205D modifications. IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10). Additionally, the IL-10 fusions can utilize IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 54  depicts total protein yield (all protein as purified by Protein A in purification part 1; mg/L), percent homodimer and percent heterodimer (as determined by analytical cation exchange separation of Protein A purified material), and homodimer and heterodimer yield (calculated based on total protein yield and percentage homodimer or heterodimer) for XENP25880, XENP25981, XENP25986, and XENP25993 from production batch 20180213. The data show that scIL10-heteroFc fusions comprising IL-10 variants with N45D (and N205D) substitution had enhanced heterodimer yield. 
         FIG. 55  depicts sequences for illustrative IL-10 monomer variants designed with the aim to remove potential for deamidation. It should be noted that these IL-10 variant sequences are based on the IL-10(109L) sequence, although they can be based on the IL-10(109H) sequence. Each of the substitutions herein can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. Additionally, as will be clear to those skilled in the art, while the substitutions herein are depicted in the context of an IL-10 monomer, each of the substitutions can be used alone or in combination in the context of IL-10 domains (e.g. hIL-10(A-D) and hIL-10(E-F)), scIL-10, and IL10M1. 
         FIG. 56A - FIG. 56C  depict sequences for illustrative scIL-10 variants designed with the aim to remove potential for deamidation. It should be noted that these IL-10 variant sequences are based on the IL-10(109L) sequence, although they can also be based on the IL-10(109H) sequence. It should also be noted that while these IL-10 variant sequences include N45D substitution for improving yield, they can be used without N45D substitution. Each of the substitutions depicted in this Figure can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. It should also be noted that these scIL-10 variants can optionally include a linker between each IL-10 sequence, although numbering of the substitutions would be based on the full-length scIL-10 sequence as depicted in  FIGS. 15A-15D . 
         FIG. 57  depicts sequences for illustrative IL-10 monomer variants designed with the aim to remove potential for aspartic acid isomerization. It should be noted that these IL-10 variant sequences are based on the IL-10(109L) sequence, although they can be based on the IL-10(109H) sequence. Each of the substitutions herein can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. Additionally, as will be clear to those skilled in the art, while the substitutions herein are depicted in the context of an IL-10 monomer, each of the substitutions can be used alone or in combination in the context of IL-10 domains (e.g. hIL-10(A-D) and hIL-10(E-F)), scIL-10, and IL10M1. 
         FIG. 58  depicts sequences for illustrative scIL-10 variants designed with the aim to remove potential for aspartic acid isomerization. It should be noted that these IL-10 variant sequences are based on the IL-10(109L) sequence, although they can also be based on the IL-10(109H) sequence. It should also be noted that while these IL-10 variant sequences include N45D substitution for improving yield, they can be used without N45D substitution. Each of the substitutions depicted in this Figure can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yields, remove charge variants, remove glycosylation sites, and/or improve stability. It should also be noted that these scIL-10 variants can optionally include a linker between each IL-10 sequence, although numbering of the substitutions would be based on the full-length scIL-10 sequence as depicted in  FIGS. 15A - FIG. 15D . 
         FIG. 59A - FIG. 59H  depict the sequences illustrative IL-10 fusions of the scIL10-Fc category in the scIL10-heteroFc format comprising scIL-10 variants engineered with the aim to remove potential for degradation-related PTMs. IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 60  depicts the sequences illustrative IL-10 fusions of the scIL10-Fc category in the heteroFc-scIL10 format comprising scIL-10 variants engineered with the aim to remove potential for degradation-related PTMs. IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 61A - FIG. 61D  depict the analytical cation exchange separation profile for Protein A purified (purification part 1) samples of A) XENP25981, B) XENP28641, and C) XENP28635, illustrating the removal of charged variants. 
         FIG. 62A - FIG. 62E  depict the induction of STAT3 phosphorylation by scIL10-heteroFc fusions comprising scIL-10 variants engineered to remove potential degradation sites on A) CD4 + CD45RA −  T cells, B) CD4 + CD45RA +  T cells, C) CD8 + CD45RA −  T cells, D) CD8 + CD45RA +  T cells, and E) Tregs. The data shows that scIL-10 variants engineered to remove potential degradation sites did not lose their activity. 
         FIG. 63A - FIG. 63C  the potentiation of A) IFNγ secretion, B) proliferation (as indicated by percentage cells expressing Ki67), and C) activation (as indicated by CD25 expression) of purified CD8 +  T cells by scIL10-heteroFc fusions comprising scIL-10 variants engineered to remove potential degradation sites. The data shows that scIL-10 variants engineered to remove potential degradation sites did not lose their activity. 
         FIG. 64  depicts sequences for illustrative IL-10 monomer variants designed with the aim to remove potential N-glycosylation sites. It should be noted that these IL-10 variant sequences are based on the IL-10(109L) sequence, although they can be based on the IL-10(109H) sequence. Each of the substitutions herein can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. Additionally, as will be clear to those skilled in the art, while the substitutions herein are depicted in the context of an IL-10 monomer, each of the substitutions can be used alone or in combination in the context of IL-10 domains (e.g. hIL-10(A-D) and hIL-10(E-F)), scIL-10, and IL10M1. 
         FIG. 65A - FIG. 65B  depict sequences for illustrative scIL-10 variants designed with the aim to remove potential N-glycosylation sites. It should be noted that these IL-10 variant sequences are based on the IL-10(109L) sequence, although they can also be based on the IL-10(109H) sequence. It should also be noted that while these IL-10 variant sequences include N45D substitution for improving yield, they can be used without N45D substitution. Each of the substitutions depicted in this Figure can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. It should also be noted that these scIL-10 variants can optionally include a linker between each IL-10 sequence, although numbering of the substitutions would be based on the full-length scIL-10 sequence as depicted in  FIG. 15C . 
         FIG. 66A - FIG. 66D  depict the sequences illustrative IL-10 fusions of the scIL10-Fc category in the scIL10-heteroFc format comprising scIL-10 variants engineered with the aim to remove potential N-glycosylation sites. IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 67  depicts sequences for illustrative IL-10 monomer variants designed with the aim to remove disulfide bridges. It should be noted that these IL-10 variant sequences are based on the IL-10(109L) sequence, although they can be based on the IL-10(109H) sequence. Each of the substitutions herein can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. Additionally, as will be clear to those skilled in the art, while the substitutions herein are depicted in the context of an IL-10 monomer, each of the substitutions can be used alone or in combination in the context of IL-10 domains (e.g. hIL-10(A-D) and hIL-10(E-F)), scIL-10, and IL10M1. 
         FIG. 68  depicts sequences for illustrative scIL-10 variants designed with the aim to remove disulfide bridges. It should be noted that these IL-10 variant sequences are based on the IL-10(109L) sequence, although they can also be based on the IL-10(109H) sequence. It should also be noted that while these IL-10 variant sequences include N45D substitution for improving yield, they can be used without N45D substitution. It should further be noted that while these IL-10 variant sequences include N320A substitution to reduce potential for deamidation, they can be used without the N320A substitution. Each of the substitutions depicted in this Figure can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. It should also be noted that these scIL-10 variants can optionally include a linker between each IL-10 sequence, although numbering of the substitutions would be based on the full-length scIL-10 sequence as depicted in  FIG. 15C . 
         FIG. 69  depicts the sequences illustrative IL-10 fusions of the scIL10-Fc category in the scIL10-heteroFc format comprising scIL-10 variants engineered with the aim to remove disulfide bridges. IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 70A - FIG. 70B  depict sequences for illustrative IL10M1 variants designed with the aim to introduce additional disulfide bridge(s) or remove disulfide bridge(s). It should be noted that these IL-10 variant sequences are based on the IL-10(109H) sequence, although they can also be based on the IL-10(109L) sequence. Each of the substitutions depicted in this Figure can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. Additionally, as will be clear to those skilled in the art, while the substitutions herein were designed in the context of an IL10M1, each of the substitutions may find use in the context of IL-10 monomers, IL-10 domains (e.g. hIL-10(A-D) and hIL-10(E-F)), and scIL-10. 
         FIG. 71A - FIG. 71E  depict the sequences illustrative IL-10 fusions of the IL10M1-Fc category in the (IL10M1)1-heteroFc format comprising IL10M1 variants designed with the aim to introduce additional disulfide bridge(s) or remove disulfide bridge(s). IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109H (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109L (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 72A - FIG. 72AQ  depict the effect of in silico point mutations at IL10M1 core residues on its affinity for IL10M1 and its stability. WT indicates wild-type residue, pos indicates position in IL-10 (numbering according to the human IL-10 mature form sequence), and mut indicates substitution. The predictions depicted in this Figure provided the background for engineering IL10M1 variants having improved stability. 
         FIG. 73  depicts sequences for illustrative IL10M1 variants designed with the aim to improve stability. It should be noted that these IL-10 variant sequences are based on the IL-10(109H) sequence, although they can also be based on the IL-10(109L) sequence. Each of the substitutions depicted in this Figure can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. Additionally, as will be clear to those skilled in the art, while the substitutions herein were designed in the context of an IL10M1, each of the substitutions may find use in the context of IL-10 monomers, IL-10 domains (e.g. hIL-10(A-D) and hIL-10(E-F)), and scIL-10. 
         FIG. 74A - FIG. 74B  depict the sequences illustrative IL-10 fusions of the IL10M1-Fc category in the (IL10M1) 1 -heteroFc format comprising IL10M1 variants engineered with the aim to improve stability. IL-10M1 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL10M1, linkers, and Fc regions. It should be noted that while the IL10M1 sequence depicted herein comprise 109H (numbered according to mature form IL-10 monomer without an internal linker), the IL-10 fusion can utilize an IL10M1 sequence comprising 109L, as well as IL10M1 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions. 
         FIG. 75A - FIG. 75B  depict sequences for illustrative IL10M1 variants designed with alternative linkers between helices D and E with the aim to increase rigidity or to increase flexibility. It should be noted that these IL-10 variant sequences are based on the IL-10(109H) sequence, although they can be based on the IL-10(109L) sequence. Each of the IL10M1 sequences depicted in this Figure can include one or more substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 76A - FIG. 76D  depict the sequences illustrative IL-10 fusions of the IL10M1-Fc category in the (IL10M1) 1 -heteroFc format comprising IL10M1 variants engineered with alternative linkers between helices D and E with the aim to increase rigidity or to increase flexibility. IL-10M1 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL10M1, linkers, and Fc regions. It should be noted that while the IL10M1 sequence depicted herein comprise 109H (numbered according to mature form IL-10 monomer without an internal linker), the IL-10 fusion can utilize an IL10M1 sequence comprising 109L, as well as IL10M1 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 77A - FIG. 77B  depict sequences for preferred IL-10 variants engineered in the context of the IL-10(109H) sequence. Each of the substitutions depicted in this Figure can be used alone or in combination with any other substitutions depicted herein, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 78A - FIG. 78G  depict illustrative sequences for IL-10 fusions of the scIL10-Fc category in the scIL10-heteroFc format comprising preferred IL-10 variants engineered in the context of the IL-10 IL-10(109H) sequence. IL-10 sequences are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 components, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109H (and 269H, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109L (and 269L, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 79A - FIG. 79G  depict illustrative sequences for IL-10 fusions of the scIL10-Fc category in the heteroFc-scIL10 format comprising preferred IL-10 variants engineered in the context of the IL-10 IL-10(109H) sequence. IL-10 sequences are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 components, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109H (and 269H, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109L (and 269L, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 80A - FIG. 80J  depict the induction of STAT3 phosphorylation on CD4 + CD45RA +  T cells by A) illustrative IL-10 fusions based on 109H variants; B) XENP27220 vs. XENP30004; C) XENP27226 vs. XENP30008; D) XENP27991 vs. XENP30009; E) XENP27990 vs. XENP30010; F) XENP27993 vs. XENP30011; G) XENP27222 vs. XENP30012; H) XENP25986 vs. XENP30013; I) XENP25993 vs. XENP30014; and J) XENP25981 vs. XENP30005. 
         FIG. 81A - FIG. 81J  depict the induction of STAT3 phosphorylation on CD4 + CD45RA −  T cells by A) illustrative IL-10 fusions based on 109H variants; B) XENP27220 vs. XENP30004; C) XENP27226 vs. XENP30008; D) XENP27991 vs. XENP30009; E) XENP27990 vs. XENP30010; F) XENP27993 vs. XENP30011; G) XENP27222 vs. XENP30012; H) XENP25986 vs. XENP30013; I) XENP25993 vs. XENP30014; and J) XENP25981 vs. XENP30005. 
         FIG. 82A - FIG. 82J  depict the induction of STAT3 phosphorylation on CD8 + CD45RA +  T cells by A) illustrative IL-10 fusions based on 109H variants; B) XENP27220 vs. XENP30004; C) XENP27226 vs. XENP30008; D) XENP27991 vs. XENP30009; E) XENP27990 vs. XENP30010; F) XENP27993 vs. XENP30011; G) XENP27222 vs. XENP30012; H) XENP25986 vs. XENP30013; I) XENP25993 vs. XENP30014; and J) XENP25981 vs. XENP30005. 
         FIG. 83A - FIG. 83J  depict the induction of STAT3 phosphorylation on CD8 + CD45RA −  T cells by A) illustrative IL-10 fusions based on 109H variants; B) XENP27220 vs. XENP30004; C) XENP27226 vs. XENP30008; D) XENP27991 vs. XENP30009; E) XENP27990 vs. XENP30010; F) XENP27993 vs. XENP30011; G) XENP27222 vs. XENP30012; H) XENP25986 vs. XENP30013; I) XENP25993 vs. XENP30014; and J) XENP25981 vs. XENP30005. 
         FIG. 84 - FIG. 84J  depict the induction of STAT3 phosphorylation on Tregs by A) illustrative IL-10 fusions based on 109H variants; B) XENP27220 vs. XENP30004; C) XENP27226 vs. XENP30008; D) XENP27991 vs. XENP30009; E) XENP27990 vs. XENP30010; F) XENP27993 vs. XENP30011; G) XENP27222 vs. XENP30012; H) XENP25986 vs. XENP30013; I) XENP25993 vs. XENP30014; and J) XENP25981 vs. XENP30005. 
         FIG. 85A - FIG. 85J  depicts the induction of STAT3 phosphorylation on monocytes by A) illustrative IL-10 fusions based on 109H variants; B) XENP27220 vs. XENP30004; C) XENP27226 vs. XENP30008; D) XENP27991 vs. XENP30009; E) XENP27990 vs. XENP30010; F) XENP27993 vs. XENP30011; G) XENP27222 vs. XENP30012; H) XENP25986 vs. XENP30013; I) XENP25993 vs. XENP30014; and J) XENP25981 vs. XENP30005. 
         FIG. 86A - FIG. 86D  depict the sequences for illustrative IL-10 fusion proteins engineered with Xtend Fc (M428L/N434S). IL-10 sequences are underlined, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between IL-10 monomer, linkers, and Fc regions. It should be noted that while the IL-10 sequence depicted herein comprise 109L (and 269L, in the context of the scIL-10), the IL-10 fusion can utilize an IL-10 sequence comprising 109H (and 269H, in the context of the scIL-10), as well as IL-10 sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 87A - FIG. 87D  depicts illustrative formats for targeted IL-10 fusions based on the IL10-Fc category, herein referred to as the “targeted IL10-Fc” category. The “mAb-IL10” format ( FIG. 87A ) comprises two identical monomers, each monomer comprising an antigen-binding domain covalently linked to the N-terminus of a homodimeric Fc chain which is covalently linked via the C-terminus, optionally via a linker, to an IL-10 monomer. The “IL10-mAb” format ( FIG. 87B ) comprises two identical monomers, each monomer comprising an IL-10 monomer covalently linked, optionally via a linker, to an antigen-binding domain which is covalently linked to the N-terminus of a homodimeric Fc chain. The “mAb-central-IL10” format ( FIG. 87C ) comprises two identical monomers, each monomer comprising an antigen-binding domain covalently linked to an IL-10 monomer which is covalently linked, optionally via a linker, to a homodimeric Fc chain. It should be noted that while the antigen-binding domains are depicted as Fabs, the antigen-binding domain can be any antigen binding molecule as defined herein, such as an scFv. The “anti-X×IL10-heteroFc” format ( FIG. 87D ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first IL-10 monomer covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker), and a second IL-10 monomer transfected separately so that it forms a non-covalent interaction with the first IL-10 monomer. 
         FIG. 88A - FIG. 88E  depict illustrative formats for targeted IL-10 fusions based on the scIL10-Fc category, herein referred to as the “targeted scIL10-Fc” category. The “anti-X×scIL10-heteroFc” format ( FIG. 88A ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker). In one aspect, the “anti-X× heteroFc-scIL10” format ( FIG. 88B ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a second heterodimeric Fc chain covalently linked via the C-terminus to a scIL-10 (optionally via a domain linker). In another aspect, the “anti-X× heteroFc-scIL10” format comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain which is covalently linked via the C-terminus to a scIL-10 (optionally via a domain linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. The “(anti-X)2-heteroFc-scIL10” format ( FIG. 88C ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to the N-terminus of a second heterodimeric Fc chain which is covalently linked via the C-terminus to a scIL-10 (optionally via a domain linker). The “(anti-X)2-central-scIL10” format ( FIG. 88D ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to a scIL-10 which is covalently linked to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). The “scIL10-(anti-X)2-heteroFc” format ( FIG. 88E ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently linked, optionally via a linker, to an antigen-binding domain which is covalently linked to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). It should be noted that while the antigen-binding domains are depicted as Fabs, the antigen-binding domain can be any antigen binding molecule as defined herein, such as an scFv. 
         FIG. 89A - FIG. 89M  depict illustrative formats for targeted IL-10 fusions based on the IL10M1-Fc category, herein referred to as the “targeted IL10M1-Fc” category. The “anti-X×(IL10M1) 1 -heteroFc” format ( FIG. 89A ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an IL10M1 covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker). In one aspect, the “anti-X× heteroFc-(IL10M1) 1 ” format ( FIG. 89B ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a second heterodimeric Fc chain covalently linked via the C-terminus to an IL10M1 (optionally via a domain linker). In another aspect, the “anti-X× heteroFc-(IL10M1) 1 ” format comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain which is covalently linked via the C-terminus to an IL10M1 (optionally via a domain linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. The “(anti-X)2-heteroFc-(IL10M1) 1 ” format ( FIG. 89C ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to the N-terminus of a second heterodimeric Fc chain which is covalently linked via the C-terminus to an IL10M1 (optionally via a domain linker). The “(IL10M1)1-(anti-X)2-heteroFc” format ( FIG. 89D ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an IL10M1 covalently linked, optionally via a linker, to an antigen-binding domain which is covalently linked to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). The “(anti-X)2-central-(IL10M1)1” format ( FIG. 89E ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to an IL10M1 which is covalently linked to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). The “anti-X×(IL10M1) 2 -heteroFc” format ( FIG. 89F ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first IL10M1 covalently attached, optionally via a domain linker, to a second IL10M1 which is covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker). In one aspect, the “anti-X× heteroFc-(IL10M1) 2 ” format ( FIG. 89G ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a second heterodimeric Fc chain covalently linked via the C-terminus to a first IL10M1 (optionally via a domain linker) which is covalently attached, optionally via a domain linker, to a second IL10M1. In another aspect, the “anti-X× heteroFc-(IL10M1) 2 ” format comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain which is covalently linked via the C-terminus to a first IL10M1 (optionally via a domain linker) which is covalently linked, optionally via a domain linker, to a second IL10M1, and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. The “(anti-X) 2 -heteroFc-(IL10M1) 2 ” format ( FIG. 89H ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to the N-terminus of a second heterodimeric Fc chain which is covalently linked via the C-terminus to a first IL10M1 (optionally via a domain linker) which is covalently attached, optionally via a domain linker, to a second IL10M1. The “(IL10M1) 2 -(anti-X) 2 -heteroFc” format ( FIG. 89I ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first IL10M1 covalently linked, optionally via a linker, to a second IL10M1 which is covalently attached (optionally via a domain linker) to an antigen-binding domain which is covalently linked to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). The “(anti-X) 2 -central-(IL10M1) 2 ” format ( FIG. 89J ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to a first IL10M1 which is covalently linked, optionally via a domain linker, to a second IL10M1 which is covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). The “mAb-(IL10M1) 2 ” format ( FIG. 89K ) comprises two identical monomers, each monomer comprising an antigen-binding domain covalently linked to the N-terminus of a homodimeric Fc chain which is covalently linked via the C-terminus, optionally via a linker, to an IL10M1. The “(IL10M1) 2 -mAb” format ( FIG. 89L ) comprises two identical monomers, each monomer comprising an IL10M1 covalently linked, optionally via a linker, to an antigen-binding domain which is covalently linked to the N-terminus of a homodimeric Fc chain. The “mAb-central-(IL10M1) 2 ” format ( FIG. 89M ) comprises two identical monomers, each monomer comprising an antigen-binding domain covalently linked to an IL10M1 which is covalently linked, optionally via a linker, to a homodimeric Fc chain. It should be noted that while the antigen-binding domains are depicted as Fabs, the antigen-binding domain can be any antigen binding molecule as defined herein, such as an scFv. 
         FIG. 90A-90H  depicts illustrative formats for targeted IL-10 fusions based on the splitIL10-Fc category, herein referred to as the “targeted splitIL10-Fc” category. In one aspect, the “anti-X×(splitIL10) 1 -heteroFc” format ( FIG. 90A ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a hIL-10(A-D) domain covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker), and a hIL-10(E-F) domain transfected separately so that it non-covalently interacts with the hIL-10(A-D) domain. In another aspect, the “anti-X×(splitIL10) 1 -heteroFc” format comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a hIL-10(E-F) domain covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker), and a hIL-10(A-D) domain transfected separately so that it non-covalently interacts with the hIL-10(E-F) domain. The “(anti-X) 2 × heteroFc-(splitIL10) 1 ” format ( FIG. 90B ) comprises a first monomer comprising an antigen-binding domain covalently attached to the N-terminus of a first heterodimeric Fc chain which is covalently linked via the C-terminus to a hIL-10(A-D) domain and a second monomer comprising an antigen-binding domain covalently linked to the N-terminus of a second heterodimeric Fc chain covalently linked via the C-terminus to a hIL-10(E-F) domain. The “(splitIL10) 1 -(anti-X) 2 -heteroFc” format ( FIG. 90C ) comprises a first monomer comprising an hIL-10(A-D) domain covalently attached to an antigen-binding domain which is covalently attached to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an hIL-10(E-F) domain covalently attached to an antigen-binding domain which is covalently attached to the N-terminus of a second heterodimeric Fc chain. The “(anti-X) 2 -central-(splitIL10) 1 -heteroFc” format ( FIG. 90D ) comprises a first monomer comprising an antigen-binding domain covalently attached to a hIL-10(A-D) domain which is covalently attached to a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently attached to a hIL-10(E-F) domain which is covalently attached to a second heterodimeric Fc chain. In one aspect, the “anti-X×(splitIL10) 2 -heteroFc” format ( FIG. 90E ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first hIL-10(A-D) domain covalently attached to a second hIL-10(A-D) domain which is covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker), and a first hIL-10(E-F) domain covalently attached to a second hIL-10(E-F) domain transfected separately so that they non-covalently interacts with the hIL-10(A-D) domains. In another aspect, the “anti-X×(splitIL10)2-heteroFc” format comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first hIL-10(E-F) domain covalently attached to a second hIL-10(E-F) domain which is covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker), and a first hIL-10(A-D) domain covalently attached to a second hIL-10(A-D) domain transfected separately so that they non-covalently interact with the hIL-10(E-F) domains. The “(anti-X) 2 × heteroFc-(splitIL10) 2 ” format ( FIG. 90F ) comprises a first monomer comprising an antigen-binding domain covalently attached to the N-terminus of a first heterodimeric Fc chain which is covalently linked via the C-terminus to a first hIL-10(A-D) domain covalently attached to a second hIL-10(A-D) domain and a second monomer comprising an antigen-binding domain covalently linked to the N-terminus of a second heterodimeric Fc chain covalently linked via the C-terminus to a first hIL-10(E-F) domain covalently attached to a second hIL-10(E-F) domain. The “(splitIL10)2-(anti-X) 2 -heteroFc” format ( FIG. 90G ) comprises a first monomer comprising a first hIL-10(A-D) domain covalently attached to a second hIL-10(A-D) domain which is covalently attached to an antigen-binding domain which is covalently attached to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first hIL-10(E-F) domain covalently attached to a second hIL-10(E-F) domain which is covalently attached to an antigen-binding domain which is covalently attached to the N-terminus of a second heterodimeric Fc chain. The “(anti-X) 2 -central-(splitIL10) 2 -heteroFc” format ( FIG. 90H ) comprises a first monomer comprising an antigen-binding domain covalently attached to a first hIL-10(A-D) domain which is covalently attached to a second hIL-10(A-D) domain which is covalently attached to a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently attached to a first hIL-10(E-F) domain which is covalently attached to a second hIL-10(E-F) domain which is covalently attached to a second heterodimeric Fc chain. 
         FIG. 91A - FIG. 91B  depict sequences for control RSV-targeted IL-10 fusions. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the RSV-targeted IL-10 fusion proteins of the invention. 
         FIG. 92  depicts V H  and V L  domain sequences for an illustrative humanized anti-CD8 antibodies. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the CD8-targeted IL-10 fusion proteins of the invention. 
         FIG. 93A - FIG. 93C  depict V H  and V L  domain sequences for an illustrative anti-NKG2D antibody. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the NKG2D-targeted IL-10 fusion proteins of the invention. 
         FIG. 94  depicts sequences for illustrative CD8-targeted IL-10 fusions in the “anti-X×(IL10M1) 1 -heteroFc” format. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the CD8-targeted IL-10 fusion proteins of the invention. 
         FIG. 95  depicts sequences for illustrative CD8-targeted IL-10 fusions in the “mAb-(IL10M1) 2 ” format. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the CD8-targeted IL-10 fusion proteins of the invention. 
         FIG. 96A - FIG. 96C  depict sequences for illustrative CD8-targeted IL-10 fusions in the “anti-X×scIL10-heteroFc” format. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the CD8-targeted IL-10 fusion proteins of the invention. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the sequences can also comprise 109H, as well as sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 97A - FIG. 97C  depict sequences for illustrative NKG2D-targeted IL-10 fusions in the “anti-X×scIL10-heteroFc” format. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the NKG2D-targeted IL-10 fusion proteins of the invention. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the sequences can also comprise 109H, as well as sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 98  depicts sequences for an illustrative CD8-targeted IL-10 fusion in the “anti-X×scIL10-heteroFc” format comprising an illustrative IL-10 potency variant. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the CD8-targeted IL-10 fusion proteins of the invention. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the sequences can also comprise 109H, as well as sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 99A - FIG. 99E  depict the induction of STAT3 phosphorylation by CD8- and NKG2D-targeted IL-10 fusions on A) CD4 + CD45RA −  T cells, B) CD4 + CD45RA +  T cells, C) CD8 + CD45RA −  T cells, D) CD8 + CD45RA +  T cells, and E) Tregs. The data show that CD8-targeted IL-10 fusion XENP25794 induced STAT3 phosphorylation on CD8 +  T cells much more potently than the non-targeted IL-10 fusion (XENP25880). In addition, the NKG2D-targeted IL-10 fusion (XENP25952) also showed a selectivity for CD8 +  T cells over CD4 +  T cells. 
         FIG. 100A - FIG. 100G  depict V H  and V L  domain sequences for an illustrative humanized anti-PD-1 antibody. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the PD-1-targeted IL-10 fusion proteins of the invention. 
         FIG. 101  depicts sequences for illustrative PD-1-targeted IL-10 fusions in the “anti-X×scIL10-heteroFc” format. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the PD-1-targeted IL-10 fusion proteins of the invention. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the sequences can also comprise 109H, as well as sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 102A - FIG. 102C  depict sequences for illustrative PD-1-targeted IL-10 fusion in the “anti-X×scIL10-heteroFc” format comprising illustrative IL-10 potency variants. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the PD-1-targeted IL-10 fusion proteins of the invention. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the sequences can also comprise 109H, as well as sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 103  depicts sequences for illustrative PD-1-targeted IL-10 fusion in the “anti-X×heteroFc-scIL10” format comprising illustrative IL-10 potency variants. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the PD-1-targeted IL-10 fusion proteins of the invention. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the sequences can also comprise 109H, as well as sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 104A - FIG. 104B  depict the sequences for illustrative humanized variable regions of non-competing anti-PD-1 mAb A, mAb B, and mAb C. The CDRs are in bold, and the slashes indicate the borders of the variable domains. As note herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the PD-1-targeted IL-10 fusion proteins of the invention. 
         FIG. 105  depicts epitope binning of a bivalent anti-PD-1 mAb based on nivolumab, in-house produced pembrolizumab, chimeric mAb A, chimeric mAb B, and chimeric mAb C as indicated by normalized BLI-response Octet. Normalized BLI-response greater than 0.5 indicate that an antibody pair does not bin to the same epitope. 
         FIG. 106A - FIG. 106C  depict sequences for illustrative non-competing PD-1-targeted IL-10 fusion comprising illustrative IL-10 potency variants. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the PD-1-targeted IL-10 fusion proteins of the invention. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the sequences can also comprise 109H, as well as sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 107A - FIG. 107E  depict the induction of STAT3 phosphorylation by a PD-1-targeted IL-10 fusion on A) CD4 + CD45RA −  CD25 +  T cells, B) CD4 + CD45RA + CD25 +  T cells, C) CD8 + CD45RA low CD25 high  T cells, D) CD8 + CD45RA high CD25 int  T cells, and E) Tregs. The data show that the PD-1-targeted IL-10 fusion induced STAT3 phosphorylation on various T cell populations much more potently than the non-targeted IL-10 fusion (XENP25880). 
         FIG. 108A - FIG. 108C  depict the potentiation of A) IFNγ secretion, B) proliferation (as indicated by percentage cells expressing Ki67), and C) activation (as indicated by CD25 expression) of purified CD8 +  T cells by PD-1-targeted IL-10 fusions. 
         FIG. 109  depicts induction of CD8 +  T cell proliferation (as indicated by percentage CD8 + Ki67+ of total CD8 +  T cell population) by untargeted IL-10 fusion proteins (XENP30007, XENP30008, and XENP30010) and PD-1 targeted IL-10 fusion proteins (XENP30520, XENP30521, and XENP30522) having different scIL-10 potency variants. The data show that for each of the reduced potency IL-10-Fc fusions, potency on induction of CD8 +  T cells was restored by PD-1-targeting. 
         FIG. 110  depicts induction of STAT3 phosphorylation on CD8 + PD-1 +  T cells by targeted IL-10 fusion proteins having PD-1-targeting arm based on mAb C_H1_L1.1 (XENP30521, XENP31266, XENP31268, and XENP31267), a PD-1-targeting arm based on 1C11 (XENP31270, XENP31269, XENP31272, and XENP31271), or a RSV-targeting arm based on Numax/motavizumab (XENP31274, XENP31273, XENP31276, and XENP31275). The data show that the PD-1-targeted IL-10 fusion proteins were more potent than the corresponding RSV-targeted IL-10 fusion proteins (that is having the same IL-10 variant and same terminal attachment). For the weaker potency IL-10 fusion proteins (having IL10.105), C-terminal attachment of the scIL-10 moiety resulted in reduced potency; and for the stronger potency IL-10 fusion protein, C-terminal attachment of the scIL-10 moiety resulted in enhanced potency. 
         FIG. 111  depicts the sequences for TIGIT for both human and cynomolgus monkey to facilitate the development of antigen binding domains that bind to both for ease of clinical development. 
         FIG. 112  depicts sequences for a phage-derived anti-TIGIT antibody with an ablation variant (E233P/L234V/L235A/G236del/S267K, “IgG1_PVA_/S267k”). The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on the numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. 
         FIG. 113  depicts the sequences for XENP19351, a bivalent anti-TIGIT mAb based on 10A7 as described in WO 2015/009856, a known blocker of TIGIT/TIGIT ligand interaction. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on the numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. 
         FIG. 114  depicts the sequences for XENP19352, a bivalent anti-TIGIT mAb based on 1F4 as described in WO 2015/009856, a known non-blocker of TIGIT/TIGIT ligand interaction. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on the numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. 
         FIG. 115  depicts mean MFI within the single cell gate (indicating binding of phage clones to Jurkat-TIGIT cells) in each well of an illustrative plate containing clone 2A5B4. 
         FIG. 116 . Jurkat-TIGIT cells within the single cell gate are represented in single parameter histograms (corresponding to each well of an illustrative plate containing clone 2A5B4) to evaluate the relative binding of phage clones with overlay of a control population. 
         FIG. 117  depicts the binding of XENP27507 (bivalent anti-TIGIT mAb based on 2A5B4), five additional phage-derived anti-TIGIT mAbs as comparators, XENP19351 (control based on 10A7 as described in WO 2015/009856), and a commercial anti-TIGIT antibody to TIGIT-transfected Jurkat cells. The data show a range of binding efficacy and potency. 
         FIG. 118  depicts apparent dissociation constant (K D ), association rate (k a ), and dissociation rate (k d ) of XENP27507 (bivalent anti-TIGIT mAb based on 2A5B4), five additional phage-derived anti-TIGIT mAbs as comparators, and XENP19351 (control based on 10A7 as described in WO 2015/009856) for human and cynomolgus TIGIT as determined by Octet. The data show that each of the clones bound both human and cynomolgus TIGIT with a range of affinities. 
         FIG. 119  depicts epitope binning of XENP27507 (bivalent anti-TIGIT mAb based on 2A5B4) and five additional phage-derived anti-TIGIT mAbs as comparators with XENP19351 (a confirmed blocker of TIGIT:TIGIT ligand interaction) and XENP19352 (a confirmed non-blocker of TIGIT:TIGIT ligand interaction) as indicated by normalized BLI-response Octet. Normalized BLI-response greater than 0.5 indicate that an antibody pair does not bin to the same epitope. The data show that each of the phage-derived mAbs binned to the same epitope as XENP19351, suggesting that they are also blockers of TIGIT:TIGIT ligand interactions. 
         FIG. 120A - FIG. 120B  depicts binding of TIGIT-mFc (incubated with indicated concentrations of XENP27507, five additional phage-derived anti-TIGIT mAbs, positive control XENP19351, and negative control anti-RSV mAb XENP15074) to A) CD112-transfected CHO cells and B) PVR-transfected CHO cells. The data show that each of the phage-derived mAbs dose-dependently blocked the binding of TIGIT to its ligands (CD112 and PVR). 
         FIG. 121A - FIG. 121B  depict the percentage of blockade of TIGIT-mFc to A) CD112-transfected CHO cells and B) PVR-transfected CHO cells by indicated concentrations of XENP27507, five additional phage-derived anti-TIGIT mAbs as comparators, positive control XENP19351, and negative control PBS. The data show that each of the phage-derived mAbs dose-dependently blocked the binding of TIGIT to its ligands (CD112 and PVR). 
         FIG. 122A - FIG. 122C  depict the variable heavy and variable light chains for illustrative anti-TIGIT ABDs which find use in the formats of the invention. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on the numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. 
         FIG. 123A - FIG. 123B  depict sequences for illustrative TIGIT-targeted IL-10 fusion comprising illustrative IL-10 potency variants. IL-10 components are italicized, linkers are double underlined (although as will be appreciated by those in the art, the linkers can be replaced by other linkers), and slashes (/) indicate the border(s) between the IL-10 components, variable regions, and constant/Fc regions. The CDRs are underlined. As noted herein and is true for every sequence herein containing CDRs, the exact identification of the CDR locations may be slightly different depending on numbering used as is shown in Table 1, and thus included herein are not only the CDRs that are underlined but also CDRs included within the V H  and V L  domains using other numbering systems. As will be appreciated by those in the art, the V H  and V L  domains can be formatted as Fab or scFvs for use in the TIGIT-targeted IL-10 fusion proteins of the invention. It should be noted that while the IL-10 sequence depicted herein comprise 109L, the sequences can also comprise 109H, as well as sequences that are 90, 95, 98 and 99% identical (as defined herein), and/or contain from 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 additional amino acid substitutions, including substitutions to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
         FIG. 124  depicts induction of CD8 +  T cell proliferation (as indicated by percentage CD8 + Ki67+ of total CD8 +  T cell population) by untargeted IL-10 fusion proteins (XENP30007, XENP30008, and XENP30010) and TIGIT-targeted IL-10 fusion proteins (XENP30523, XENP30524, and XENP30525) having different scIL-10 potency variants. The data show that for each of the reduced potency IL-10-Fc fusions, potency on induction of CD8 +  T cells was restored by TIGIT-targeting. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     I. Definitions 
     In order that the application may be more completely understood, several definitions are set forth below. Such definitions are meant to encompass grammatical equivalents. 
     By “ablation” herein is meant a decrease or removal of binding and/or activity. Thus for example, “ablating FcγR binding” means the Fc region amino acid variant has less than 50% starting binding as compared to an Fc region not containing the specific variant, with less than 70-80-90-95-98% loss of binding being preferred, and in general, with the binding being below the level of detectable binding in a Biacore assay. Of particular use in the ablation of FcγR binding are those shown in  FIG. 7 . However, unless otherwise noted, the Fc monomers of the invention retain binding to the FcRn. 
     By “ADCC” or “antibody dependent cell-mediated cytotoxicity” as used herein is meant the cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause lysis of the target cell. ADCC is correlated with binding to FcγRIIIa; increased binding to FcγRIIIa leads to an increase in ADCC activity. As is discussed herein, many embodiments of the invention ablate ADCC activity entirely. 
     By “modification” herein is meant an amino acid substitution, insertion, and/or deletion in a polypeptide sequence or an alteration to a moiety chemically linked to a protein. For example, a modification may be an altered carbohydrate or PEG structure attached to a protein. By “amino acid modification” herein is meant an amino acid substitution, insertion, and/or deletion in a polypeptide sequence. For clarity, unless otherwise noted, the amino acid modification is always to an amino acid coded for by DNA, e.g., the 20 amino acids that have codons in DNA and RNA. 
     By “amino acid substitution” or “substitution” herein is meant the replacement of an amino acid at a particular position in a parent polypeptide sequence with a different amino acid. In particular, in some embodiments, the substitution is to an amino acid that is not naturally occurring at the particular position, either not naturally occurring within the organism or in any organism. For example, the substitution E272Y or 272Y refers to a variant polypeptide, in this case an Fc variant, in which the glutamic acid at position 272 is replaced with tyrosine. For clarity, a protein which has been engineered to change the nucleic acid coding sequence but not to change the starting amino acid (for example exchanging CGG (encoding arginine) to CGA (still encoding arginine) to increase host organism expression levels) is not an “amino acid substitution”; that is, despite the creation of a new gene encoding the same protein, if the protein has the same amino acid at the particular position that it started with, it is not an amino acid substitution. 
     By “amino acid insertion” or “insertion” as used herein is meant the addition of an amino acid residue or sequence at a particular position in a parent polypeptide sequence. For example, −233E designates an insertion of glutamic acid after position 233 and before position 234. Additionally, −233ADE or A233ADE designates an insertion of AlaAspGlu after position 233 and before position 234. 
     By “amino acid deletion” or “deletion” as used herein is meant the removal of an amino acid residue or sequence at a particular position in a parent polypeptide sequence. For example, E233-, E233#, E233( ) or E233del designates a deletion of glutamic acid at position 233. Additionally, EDA233- or EDA233# designates a deletion of the sequence GluAspAla that begins at position 233. 
     By “variant protein”, “protein variant”, or “variant” as used herein is meant a protein that differs from that of a parent protein by virtue of at least one modification. Protein variant may refer to the protein itself, a composition comprising the protein, the amino acid sequence that encodes it, or the DNA sequence that encodes it. Preferably, the protein variant has at least one amino acid modification compared to the parent protein, e.g. from about one to about seventy amino acid modifications, and preferably from about one to about five amino acid modifications compared to the parent. The modification can be an addition, deletion, or substitution. As described below, in some embodiments the parent polypeptide, for example an Fc parent polypeptide, is a human wild type sequence, such as the Fc region from IgG1, IgG2, IgG3 or IgG4. The protein variant sequence herein will preferably possess at least about 80% identity with a parent protein sequence, and most preferably at least about 90% identity, more preferably at least about 95-98-99% identity. 
     As used herein, by “protein” is meant at least two covalently attached amino acids, which includes proteins, polypeptides, oligopeptides and peptides. When a biologically functional molecule comprises two or more proteins, each protein may be referred to as a “monomer” or as a “subunit” or as a “domain”; and the biologically functional molecule may be referred to as a “complex”. 
     By “residue” as used herein is meant a position in a protein and its associated amino acid identity. For example, Asparagine 297 (also referred to as Asn297 or N297) is a residue at position 297 in the human antibody IgG1. 
     By “IgG subclass modification” or “isotype modification” as used herein is meant an amino acid modification that converts one amino acid of one IgG isotype to the corresponding amino acid in a different, aligned IgG isotype. For example, because IgG1 comprises a tyrosine and IgG2 a phenylalanine at EU position 296, a F296Y substitution in IgG2 is considered an IgG subclass modification. 
     By “non-naturally occurring modification” as used herein is meant an amino acid modification that is not isotypic. For example, because none of the IgGs comprise a serine at position 434, the substitution 434S in IgG1, IgG2, IgG3, or IgG4 (or hybrids thereof) is considered a non-naturally occurring modification. 
     By “amino acid” and “amino acid identity” as used herein is meant one of the 20 naturally occurring amino acids that are coded for by DNA and RNA. 
     By “effector function” as used herein is meant a biochemical event that results from the interaction of an antibody Fc region with an Fc receptor or ligand. Effector functions include but are not limited to ADCC, ADCP, and CDC. 
     By “IgG Fc ligand” or “Fc ligand” as used herein is meant a molecule, preferably a polypeptide, from any organism that binds to the Fc region of an IgG antibody to form an Fc/Fc ligand complex. Fc ligands include but are not limited to FcγRIs, FcγRIIs, FcγRIIIs, FcRn, C1q, C3, mannan binding lectin, mannose receptor, staphylococcal protein A, streptococcal protein G, and viral FcγR. Fc ligands also include Fc receptor homologs (FcRH), which are a family of Fc receptors that are homologous to the FcγRs (Davis et al., 2002, Immunological Reviews 190:123-136, entirely incorporated by reference). Fc ligands may include undiscovered molecules that bind Fc. Particular IgG Fc ligands are FcRn and Fc gamma receptors. 
     By “Fc gamma receptor”, “FcγR” or “FcgammaR” as used herein is meant any member of the family of proteins that bind the IgG antibody Fc region and is encoded by an FcγR gene. In humans this family includes but is not limited to FcγRI (CD64), including isoforms FcγRIa, FcγRIb, and FcγRIc; FcγRII (CD32), including isoforms FcγRIIa (including allotypes H131 and R131), FcγRIIb (including FcγRIIb-1 and FcγRIIb-2), and FcγRIIc; and FcγRIII (CD16), including isoforms FcγRIIIa (including allotypes V158 and F158) and FcγRIIIb (including allotypes FcγRIIb-NA1 and FcγRIIb-NA2) (Jefferis et al., 2002, Immunol Lett 82:57-65, entirely incorporated by reference), as well as any undiscovered human FcγRs or FcγR isoforms or allotypes. An FcγR may be from any organism, including but not limited to humans, mice, rats, rabbits, and monkeys. Mouse FcγRs include but are not limited to FcγRI (CD64), FcγRII (CD32), FcγRIII (CD16), and FcγRIII-2 (CD16-2), as well as any undiscovered mouse FcγRs or FcγR isoforms or allotypes. 
     By “FcRn” or “neonatal Fc receptor” as used herein is meant a protein that binds the IgG antibody Fc region and is encoded at least in part by an FcRn gene. The FcRn may be from any organism, including but not limited to humans, mice, rats, rabbits, and monkeys. As is known in the art, the functional FcRn protein comprises two polypeptides, often referred to as the heavy chain and light chain. The light chain is beta-2-microglobulin (132-microglobulin) and the heavy chain is encoded by the FcRn gene. Unless otherwise noted herein, FcRn or an FcRn protein refers to the complex of FcRn heavy chain with 42-microglobulin. A variety of Fc variants can be used to increase binding to the FcRn, and in some cases, to increase serum half-life. In general, unless otherwise noted, the Fc monomers of the invention retain binding to the FcRn (and, as noted below, can include amino acid variants to increase binding to the FcRn). 
     By “parent polypeptide” as used herein is meant a starting polypeptide that is subsequently modified to generate a variant. The parent polypeptide may be a naturally occurring polypeptide, or a variant or engineered version of a naturally occurring polypeptide. Parent polypeptide may refer to the polypeptide itself, compositions that comprise the parent polypeptide, or the amino acid sequence that encodes it. 
     By “Fc” or “Fc region” or “Fc domain” as used herein is meant the polypeptide comprising the constant region of an antibody, in some instances, excluding all of the first constant region immunoglobulin domain (e.g., CH1) or a portion thereof, and in some cases, optionally including all or part of the hinge. For IgG, the Fc domain comprises immunoglobulin domains CH2 and CH3 (Cγ2 and Cγ3), and optionally all or a portion of the hinge region between CH1 (Cγ1) and CH2 (Cγ2). Thus, in some cases, the Fc domain includes, from N- to C-terminal, CH2-CH3 and hinge-CH2-CH3. In some embodiments, the Fc domain is that from IgG1, IgG2, IgG3 or IgG4, with IgG1 hinge-CH2-CH3 and IgG4 hinge-CH2-CH3 finding particular use in many embodiments. Additionally, in the case of human IgG1 Fc domains, frequently the hinge includes a C220S amino acid substitution. Furthermore, in the case of human IgG4 Fc domains, frequently the hinge includes a S228P amino acid substitution. Although the boundaries of the Fc region may vary, the human IgG heavy chain Fc region is usually defined to include residues E216, C226, or A231 to its carboxyl-terminus, wherein the numbering is according to the EU index as in Kabat. In some embodiments, as is more fully described below, amino acid modifications are made to the Fc region, for example to alter binding to one or more FcγR or to the FcRn. 
     As will be appreciated by those in the art, the exact numbering and placement of the heavy constant region domains can be different among different numbering systems. A useful comparison of heavy constant region numbering according to EU and Kabat is as below, see Edelman et al., 1969, Proc Natl Acad Sci USA 63:78-85 and Kabat et al., 1991, Sequences of Proteins of Immunological Interest, 5th Ed., United States Public Health Service, National Institutes of Health, Bethesda, entirely incorporated by reference. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 EU Numbering 
                 Kabat Numbering 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 CH1 
                 118-215 
                 114-223 
               
               
                   
                 Hinge 
                 216-230 
                 226-243 
               
               
                   
                 CH2 
                 231-340 
                 244-360 
               
               
                   
                 CH3 
                 341-447 
                 361-478 
               
               
                   
                   
               
            
           
         
       
     
     “Fc variant” or “variant Fc” as used herein is meant a protein comprising an amino acid modification in an Fc domain. The modification can be an addition, deletion, or substitution. The Fc variants of the present invention are defined according to the amino acid modifications that compose them. Thus, for example, N434S or 434S is an Fc variant with the substitution for serine at position 434 relative to the parent Fc polypeptide, wherein the numbering is according to the EU index. Likewise, M428L/N434S defines an Fc variant with the substitutions M428L and N434S relative to the parent Fc polypeptide. The identity of the WT amino acid may be unspecified, in which case the aforementioned variant is referred to as 428L/434S. It is noted that the order in which substitutions are provided is arbitrary, that is to say that, for example, 428L/434S is the same Fc variant as 434S/428L, and so on. For all positions discussed in the present invention that relate to antibodies or derivatives and fragments thereof, unless otherwise noted, amino acid position numbering is according to the EU index. The EU index or EU index as in Kabat or EU numbering scheme refers to the numbering of the EU antibody (Edelman et al., 1969, Proc Natl Acad Sci USA 63:78-85, hereby entirely incorporated by reference). The modification can be an addition, deletion, or substitution. 
     By “fusion protein” as used herein is meant covalent joining of at least two proteins or protein domains. Fusion proteins may comprise artificial sequences, e.g. a domain linker, variant Fc domains, a variant IL-10 domain, etc. as described herein. By “Fc fusion protein” or “immunoadhesin” herein is meant a protein comprising an Fc region, generally linked (optionally through a domain linker, as described herein) to one or more different protein domains. Accordingly, an “IL-10 Fc fusion” comprises an Fc region linked (optionally but usually through a domain linker) to an IL-10, an IL-10(A-D) domain, an IL10(E-F) domain, a monomeric IL-10, and/or single-chain IL-10 complex (scIL-10), as described herein. In some instances, two Fc fusion proteins can form a homodimeric Fc fusion protein or a heterodimeric Fc fusion protein with the latter being preferred. In some cases, one monomer of the heterodimeric Fc fusion protein comprises an Fc domain alone (e.g., an empty Fc domain) and the other monomer is an Fc fusion, comprising a variant Fc domain and an IL-10 domain, as outlined herein. 
     By “position” as used herein is meant a location in the sequence of a protein. Positions may be numbered sequentially, or according to an established format, for example the EU index for antibody numbering. 
     By “strandedness” in the context of the monomers of the heterodimeric proteins of the invention herein is meant that, similar to the two strands of DNA that “match”, heterodimerization variants are incorporated into each monomer so as to preserve, create, and/or enhance the ability to “match” to form heterodimers. For example, if some pI variants are engineered into monomer A (e.g. making the pI higher), then steric variants that are “charge pairs” that can be utilized as well do not interfere with the pI variants, e.g. the charge variants that make a pI higher are put on the same “strand” or “monomer” to preserve both functionalities. Similarly, for “skew” variants that come in pairs of a set as more fully outlined below, the skilled artisan will consider pI in deciding into which strand or monomer that incorporates one set of the pair will go, such that pI separation is maximized using the pI of the skews as well. 
     By “wild type or WT” herein is meant an amino acid sequence or a nucleotide sequence that is found in nature, including allelic variations. A WT protein has an amino acid sequence or a nucleotide sequence that has not been intentionally modified. 
     The heterodimeric proteins of the present invention are generally isolated or recombinant. “Isolated,” when used to describe the various polypeptides disclosed herein, means a polypeptide that has been identified and separated and/or recovered from a cell or cell culture from which it was expressed. Ordinarily, an isolated polypeptide will be prepared by at least one purification step. An “isolated protein,” refers to a protein which is substantially free of other proteins from a cell culture such as host cell proteins. “Recombinant” means the proteins are generated using recombinant nucleic acid techniques in exogeneous host cells. 
     “Percent (%) amino acid sequence identity” with respect to a protein sequence is defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the specific (parental) sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN or Megalign (DNASTAR) software. Those skilled in the art can determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared. One particular program is the ALIGN-2 program outlined at paragraphs [0279] to [0280] of US Pub. No. 20160244525, hereby incorporated by reference. 
     The degree of identity between an amino acid sequence of the present invention (“invention sequence”) and the parental amino acid sequence is calculated as the number of exact matches in an alignment of the two sequences, divided by the length of the “invention sequence,” or the length of the parental sequence, whichever is the shortest. The result is expressed in percent identity. 
     In some embodiments, two or more amino acid sequences are at least 50%, 60%, 70%, 80%, or 90% identical. In some embodiments, two or more amino acid sequences are at least 95%, 97%, 98%, 99%, or even 100% identical. 
     By “IL-10 monomer” or “IL-10 monomer domain” herein is meant a monomer composed of 6 helices, herein referred to as helices A-F. As discussed herein, the IL10 monomer domain can be a wild-type human sequence (e.g. SEQ ID NO:1 from  FIG. 1 ) or a variant thereof (e.g. see  FIGS. 35A-35D , for example). Note that residue 109 (numbering based on mature form IL10 sequence) can be either H or L in the context of the formats and sequences described herein. 
     The IL-10 monomers of the invention, when presented together in the formats described herein, bind the IL-10 receptor, which consists of two alpha and two beta subunits (or R1 and R2 subunits). The strength, or affinity, of specific binding can be expressed in terms of dissociation constant (K D ) of the interaction, wherein a smaller K D  represents greater affinity and a larger K D  represents lower affinity. Binding properties can be determined by methods well known in the art such as bio-layer interferometry and surface plasmon resonance based methods. One such method entails measuring the rates of antigen-binding site/antigen or receptor/ligand complex association and dissociation, wherein rates depend on the concentration of the complex partners, the affinity of the interaction, and geometric parameters that equally influence the rate in both directions. Thus, both the association rate (k d ) and the dissociation rate (k d ) can be determined, and the ratio of k d /k a  is equal to the dissociation constant K D  (See Nature 361:186-187 (1993) and Davies et al. (1990) Annual Rev Biochem 59:439-473). 
     Specific binding for a particular molecule can be exhibited, for example, by a molecule having a K D  for a ligand (generally a receptor, in this case) of at least about 10 −4  M, at least about 10 −5  M, at least about 10 −6  M, at least about 10 −7  M, at least about 10 −8  M, at least about 10 −9  M, alternatively at least about 10 −10  at least about 10 −11  M, at least about 10 −12 M, or greater. Typically, a molecule that specifically binds its receptor will have a K D  that is 20-, 50-, 100-, 500-, 1000-, 5,000-, 10,000- or more times greater for a control molecule relative to the receptor. 
     Also, specific binding for a particular molecule can be exhibited, for example, by a molecule having a k a  or association rate for a ligand or receptor of at least 20-, 50-, 100-, 500-, 1000-, 5,000-, 10,000- or more times greater for the receptor relative to a control. 
     By “fused” or “covalently linked” is herein meant that the components (e.g., an IL-10 monomer domain and an Fc domain) are linked by peptide bonds, either directly or indirectly via domain linkers, outlined herein. 
     As used herein, the term “single-chain” refers to a molecule comprising amino acid domains linearly linked by peptide bonds. In certain embodiments, the biologically functional IL10 is a single chain IL-10 complex or “scIL10”, i.e. two IL-10 monomer domains are fused to form a single peptide chain. In a particular such embodiment, the C-terminus of a first IL-10 monomer is connected to the N-terminus of a second IL-10 monomer, designated herein as “scIL10”. It should be noted that these single chain constructs, where two IL-10 monomers are on the same amino acid chain, still are part of a heterodimeric molecule containing two amino acid chains (e.g. the scIL10) component and the “empty arm” Fc component). 
     II. Dimeric Fc Fusion Proteins 
     In some aspects, the present invention relates to dimeric Fc fusion proteins that include an Fc region, generally linked (optionally through a domain linker) to one or more different protein domains. 
     In one aspect, the dimeric Fc fusion protein is a homodimeric Fc fusion protein. In another aspect, the dimeric Fc fusion protein is a heterodimeric Fc fusion protein. As will be appreciated, discussion herein of components of the fusion proteins encompassed by the present disclosure is applicable to both homodimeric and heterodimeric Fc fusion proteins as appropriate, unless otherwise specified. 
     In one aspect, the dimeric Fc fusion protein is an IL-10 dimeric Fc fusion protein that includes IL-10 monomer domains in different orientations, such that they present together to bind to the IL10 receptor. The Fc domains can be derived from IgG Fc domains, e.g., IgG1, IgG2, IgG3 or IgG4 Fc domains, with IgG1 Fc domains finding particular use in the invention. As described herein, IgG1 Fc domains may be used, often, but not always in conjunction with ablation variants to ablate effector function. Similarly, when low effector function is desired, IgG4 Fc domains may be used. 
     For any of the Fc fusion proteins described herein, the carboxy-terminal portion of each chain defines a constant region primarily responsible for effector function. Kabat et al. collected numerous primary sequences of the variable regions of heavy chains and light chains. Based on the degree of conservation of the sequences, they classified individual primary sequences into the CDRs and the framework and made a list thereof (see SEQUENCES OF IMMUNOLOGICAL INTEREST, 5th edition, NIH publication, No. 91-3242, E. A. Kabat et al., entirely incorporated by reference). Throughout the present specification, the Kabat numbering system is generally used when referring to a residue in the variable domain (approximately, residues 1-107 of the light chain variable region and residues 1-113 of the heavy chain variable region) and the EU numbering system for Fc regions (e.g., Kabat et al., supra (1991)). 
     In the IgG subclass of immunoglobulins, there are several immunoglobulin domains in the heavy chain. By “immunoglobulin (Ig) domain” herein is meant a region of an immunoglobulin having a distinct tertiary structure. Of interest in the present invention are the heavy chain domains, including, the constant heavy (CH) domains and the hinge domains. In the context of IgG antibodies, the IgG isotypes each have three CH regions. Accordingly, “CH” domains in the context of IgG are as follows: “CH1” refers to positions 118-215 according to the EU index as in Kabat. “Hinge” refers to positions 216-230 according to the EU index as in Kabat. “CH2” refers to positions 231-340 according to the EU index as in Kabat, and “CH3” refers to positions 341-447 according to the EU index as in Kabat. As shown in Table 1, the exact numbering and placement of the heavy chain domains can be different among different numbering systems. As shown herein and described below, the pI variants can be in one or more of the CH regions, as well as the hinge region, discussed below. 
     In the IgG subclass of immunoglobulins, there are several immunoglobulin domains in the heavy chain. By “immunoglobulin (Ig) domain” herein is meant a region of an immunoglobulin having a distinct tertiary structure. Of interest in the present invention are the heavy chain domains, including, the constant heavy (CH) domains and the hinge domains. In the context of IgG antibodies, the IgG isotypes each have three CH regions. Accordingly, “CH” domains in the context of IgG are as follows: “CH1” refers to positions 118-215 according to the EU index as in Kabat. “Hinge” refers to positions 216-230 according to the EU index as in Kabat. “CH2” refers to positions 231-340 according to the EU index as in Kabat, and “CH3” refers to positions 341-447 according to the EU index as in Kabat. As shown in Table 1, the exact numbering and placement of the heavy chain domains can be different among different numbering systems. As shown herein and described below, the pI variants can be in one or more of the CH regions, as well as the hinge region, discussed below. 
     Another type of Ig domain of the heavy chain is the hinge region. By “hinge” or “hinge region” or “antibody hinge region” or “immunoglobulin hinge region” herein is meant the flexible polypeptide comprising the amino acids between the first and second heavy chain constant domains of an antibody. Structurally, the IgG CH1 domain ends at EU position 215, and the IgG CH2 domain begins at residue EU position 231. Thus for IgG the antibody hinge is herein defined to include positions 216 (E216 in IgG1) to 230 (P230 in IgG1), wherein the numbering is according to the EU index as in Kabat. In some embodiments, for example in the context of an Fc region, the hinge is included, generally referring to positions 216-230. As noted herein, pI variants can be made in the hinge region as well. 
     As described herein and known in the art, the dimeric proteins of the invention comprise different domains, which can be overlapping as well. These domains include, but are not limited to, the Fc domain, the CH2 domain, the CH3 domain and the hinge domain, and an IL-10 monomer domain. As described herein, these domains are linked together in different formats, as generally outlined in  FIGS. 16, 20, 23, and 29 . 
     In some embodiments described herein, when a protein domain, e.g., an IL-10 monomer, is attached to an Fc domain, it is the C-terminus of the protein domain that is attached to the N-terminus of an Fc domain. In other embodiments described herein, when a protein domain, e.g., an IL-10 monomer, is attached to an Fc domain it is the N-terminus of the protein fragment that is attached to the C-terminus of the Fc domain. 
     In some of the constructs and sequences outlined herein of an Fc domain protein, the C-terminus of the IL-10 monomer is attached to the N-terminus of a domain linker, the C-terminus of which is attached to the N-terminus of a constant Fc domain (N-IL-10 monomer domain-linker-Fc domain-C) although, as will be appreciated, the order of the components can be switched: (N-Fc domain-linker-IL-10 monomer domain-C). In other constructs and sequences outlined herein, the C-terminus of a first protein domain is attached to the N-terminus of a second protein domain, optionally via a domain linker, the C-terminus of the second protein domain is attached to the N-terminus of a constant Fc domain, optionally via a domain linker. In yet another construct, the N-terminus of a first protein domain is attached to the C-terminus of a second protein domain, optionally via a domain linker, the N-terminus of the second protein fragment is attached to the C-terminus of a constant Fc domain, optionally via a domain linker. In yet other constructs and sequences outlined herein, a constant Fc domain that is not attached to a first protein fragment or a second protein fragment is provided. A dimeric Fc fusion protein can contain two or more of the exemplary monomeric Fc domain proteins described herein—as will be appreciated, a homodimeric Fc fusion protein will contain two identical monomer Fc domain proteins, whereas a heterodimeric Fc fusion protein will contain two or more different monomer Fc domain proteins. 
     In some embodiments, the linker is a “domain linker”, used to link any two domains as outlined herein together, some of which are depicted in the figures. While any suitable linker can be used, many embodiments utilize a glycine-serine polymer, including for example (GS)n (SEQ ID NO: 34), (GSGGS)n (SEQ ID NO: 35), (GGGGS)n (SEQ ID NO: 36), and (GGGS)n (SEQ ID NO: 37), where n is an integer of at least one (and generally from 0 to 1 to 2 to 3 to 4 to 5) as well as any peptide sequence that allows for recombinant attachment of the two domains with sufficient length and flexibility to allow each domain to retain its biological function. In some cases, and with attention being paid to “strandedness”, as outlined below, the linker is a charged domain linker. 
     As noted above, the present disclosure encompasses both heterodimeric and non-heterodimeric (also referred to herein as homodimeric) formats. As will be appreciated by those in the art, such homodimeric formats can be monospecific antibodies (e.g. “traditional monoclonal antibodies” and/or Fc fusion proteins that bind to a single target) or non-heterodimeric bispecific formats. Accordingly, the present invention provides monoclonal (monospecific) Fc fusion proteins or non-heterodimeric bispecific proteins. Non-heterodimeric bispecific formats are known in the art, and include a number of different formats as generally depicted in Spiess et al., Molecular Immunology (67):95-106 (2015) and Kontermann, mAbs 4:2, 182-197 (2012), both of which are expressly incorporated by reference and in particular for the figures, legends and citations to the formats therein. 
     In some embodiments the present invention provides heterodimeric Fc fusion proteins that rely on the use of two different heavy chain variant Fc sequences, that will self-assemble to form a heterodimeric Fc domain fusion polypeptide. In one embodiment, heterodimeric Fc fusion proteins contain at least two constant domains which can be engineered to produce heterodimers, such as pI engineering. Other Fc domains that can be used include fragments that contain one or more of the CH1, CH2, CH3, and hinge domains of the invention that have been pI engineered. In particular, the formats depicted in  FIGS. 16C-D ,  20 A-B,  23 C-F, and  29 A-D are heterodimeric Fc fusion proteins, meaning that the protein has two associated Fc sequences self-assembled into a heterodimeric Fc domain and at least one protein fragment (e.g., 1, 2 or more protein fragments). In some cases, a first protein fragment is linked to a first Fc sequence and a second protein fragment is linked to a second Fc sequence. In some cases, the heterodimeric Fc fusion protein contains a first protein fragment linked to a second protein fragment which is linked to a first Fc sequence, and a second Fc sequence that is not linked to either the first or second protein fragments. 
     The present invention is directed to novel constructs to provide dimeric Fc fusion proteins that allow binding to one or more binding partners, ligands or receptors. The Fc fusion constructs are based on the self-assembling nature of the two Fc domains of the heavy chains of antibodies, e.g., two “monomers” that assemble into a “dimer”. Heterodimeric Fc fusion formats are made by altering the amino acid sequence of each monomer as more fully discussed below. Thus, the present invention is generally directed to the creation of non-heterodimeric and heterodimeric Fc fusion proteins that can co-engage binding partner(s) or ligand(s) or receptor(s) in several ways. In further embodiments, the heterodimeric Fc fusion proteins rely on amino acid variants in the constant regions that are different on each chain to promote heterodimeric formation and/or allow for ease of purification of heterodimers over the homodimers. There are a number of mechanisms that can be used to generate the heterodimers of the present invention. In addition, as will be appreciated by those in the art, these mechanisms can be combined to ensure high heterodimerization. Thus, amino acid variants that lead to the production of heterodimers are referred to as “heterodimerization variants”. As discussed below, heterodimerization variants can include steric variants (e.g. the “knobs and holes” or “skew” variants described below and the “charge pairs” variants described below) as well as “pI variants”, which allows purification of homodimers away from heterodimers. As is generally described in WO2014/145806, hereby incorporated by reference in its entirety and specifically as below for the discussion of “heterodimerization variants”, useful mechanisms for heterodimerization include “knobs and holes” (“KIH”; sometimes described herein as “skew” variants (see discussion in WO2014/145806)), “electrostatic steering” or “charge pairs” as described in WO2014/145806, pI variants as described in WO2014/145806, and general additional Fc variants as outlined in WO2014/145806 and below. 
     In the present invention, there are several basic mechanisms that can lead to ease of purifying heterodimeric proteins and antibodies; one relies on the use of pI variants, such that each monomer, and subsequently each dimeric species, has a different pI, thus allowing the isoelectric purification of A-A, A-B and B-B dimeric proteins. Alternatively, some formats also allow separation on the basis of size. As is further outlined below, it is also possible to “skew” the formation of heterodimers over homodimers. Thus, a combination of steric heterodimerization variants and pI or charge pair variants find particular use in the invention. 
     In general, embodiments of particular use in the present invention rely on sets of variants that include skew variants, that encourage heterodimerization formation over homodimerization formation, coupled with pI variants, which increase the pI difference between the two monomers and each dimeric species. 
     Additionally, as more fully outlined below, depending on the format of the heterodimer Fc fusion protein, pI variants can be either contained within the constant and/or Fc domains of a monomer, or domain linkers can be used. That is, the invention provides pI variants that are on one or both of the monomers, and/or charged domain linkers as well. In addition, additional amino acid engineering for alternative functionalities may also confer pI changes, such as Fc, FcRn and KO variants. 
     In the present invention that utilizes pI as a separation mechanism to allow the purification of heterodimeric proteins, amino acid variants can be introduced into one or both of the monomer polypeptides; that is, the pI of one of the monomers (referred to herein for simplicity as “monomer A”) can be engineered away from monomer B, or both monomer A and B can be changed, with the pI of monomer A increasing and the pI of monomer B decreasing. As discussed, the pI changes of either or both monomers can be done by removing or adding a charged residue (e.g., a neutral amino acid is replaced by a positively or negatively charged amino acid residue, e.g., glutamine to glutamic acid), changing a charged residue from positive or negative to the opposite charge (e.g. aspartic acid to lysine) or changing a charged residue to a neutral residue (e.g., loss of a charge; lysine to serine.). A number of these variants are shown in the Figures. 
     Accordingly, this embodiment of the present invention provides for creating a sufficient change in pI in at least one of the monomers such that heterodimers can be separated from homodimers. As will be appreciated by those in the art, and as discussed further below, this can be done by using a “wild type” heavy chain constant region and a variant region that has been engineered to either increase or decrease its pI (wt A: B+ or wt A: B−), or by increasing one region and decreasing the other region (A+: B− or A−: B+). 
     Thus, in general, a component of some embodiments of the present invention are amino acid variants in the constant regions that are directed to altering the isoelectric point (pI) of at least one, if not both, of the monomers of a dimeric protein by incorporating amino acid substitutions (“pI variants” or “pI substitutions”) into one or both of the monomers. The separation of the heterodimers from the two homodimers can be accomplished if the pIs of the two monomers differ by as little as 0.1 pH unit, with 0.2, 0.3, 0.4 and 0.5 or greater all finding use in the present invention. 
     As will be appreciated by those in the art, the number of pI variants to be included on each or both monomer(s) to get good separation will depend in part on the starting pI of the components. That is, to determine which monomer to engineer or in which “direction” (e.g., more positive or more negative), the sequences of the Fc domains, and in some cases, the protein domain(s) linked to the Fc domain are calculated and a decision is made from there. As is known in the art, different Fc domains and/or protein domains will have different starting pIs which are exploited in the present invention. In general, as outlined herein, the pIs are engineered to result in a total pI difference of each monomer of at least about 0.1 logs, with 0.2 to 0.5 being preferred as outlined herein. 
     Furthermore, as will be appreciated by those in the art and outlined herein, in some embodiments, heterodimers can be separated from homodimers on the basis of size. As shown in the Figures, for example, several of the formats allow separation of heterodimers and homodimers on the basis of size. 
     In the case where pI variants are used to achieve heterodimerization, by using the constant region(s) of Fc domains(s), a more modular approach to designing and purifying heterodimeric Fc fusion proteins is provided. Thus, in some embodiments, heterodimerization variants (including skew and purification heterodimerization variants) must be engineered. In addition, in some embodiments, the possibility of immunogenicity resulting from the pI variants is significantly reduced by importing pI variants from different IgG isotypes such that pI is changed without introducing significant immunogenicity. Thus, an additional problem to be solved is the elucidation of low pI constant domains with high human sequence content, e.g. the minimization or avoidance of non-human residues at any particular position. 
     A side benefit that can occur with this pI engineering is also the extension of serum half-life and increased FcRn binding. That is, as described in U.S. Ser. No. 13/194,904 (incorporated by reference in its entirety), lowering the pI of antibody constant domains (including those found in antibodies and Fc fusions) can lead to longer serum retention in vivo. These pI variants for increased serum half life also facilitate pI changes for purification. 
     In addition, it should be noted that the pI variants of the heterodimerization variants give an additional benefit for the analytics and quality control process of Fc fusion proteins, as the ability to either eliminate, minimize and distinguish when homodimers are present is significant. Similarly, the ability to reliably test the reproducibility of the heterodimeric Fc fusion protein production is important. 
     A. Heterodimerization Variants 
     The present invention provides heterodimeric proteins, including heterodimeric Fc fusion proteins in a variety of formats, which utilize heterodimeric variants to allow for heterodimer formation and/or purification away from homodimers. The heterodimeric fusion constructs are based on the self-assembling nature of the two Fc domains, e.g., two “monomers” that assemble into a “dimer”. 
     There are a number of suitable pairs of sets of heterodimerization skew variants. These variants come in “pairs” of “sets”. That is, one set of the pair is incorporated into the first monomer and the other set of the pair is incorporated into the second monomer. It should be noted that these sets do not necessarily behave as “knobs in holes” variants, with a one-to-one correspondence between a residue on one monomer and a residue on the other; that is, these pairs of sets form an interface between the two monomers that encourages heterodimer formation and discourages homodimer formation, allowing the percentage of heterodimers that spontaneously form under biological conditions to be over 90%, rather than the expected 50% (25% homodimer A/A:50% heterodimer A/B:25% homodimer B/B). 
     B. Steric Variants 
     In some embodiments, the formation of heterodimers can be facilitated by the addition of steric variants. That is, by changing amino acids in each heavy chain, different heavy chains are more likely to associate to form the heterodimeric structure than to form homodimers with the same Fc amino acid sequences. Suitable steric variants are included in the FIG. 29 of U.S. Ser. No. 15/141,350, all of which is hereby incorporated by reference in its entirety, as well as in  FIG. 5 . 
     One mechanism is generally referred to in the art as “knobs and holes”, referring to amino acid engineering that creates steric influences to favor heterodimeric formation and disfavor homodimeric formation, as described in U.S. Ser. No. 61/596,846, Ridgway et al., Protein Engineering 9(7):617 (1996); Atwell et al., J. Mol. Biol. 1997 270:26; U.S. Pat. No. 8,216,805, all of which are hereby incorporated by reference in their entirety. The Figures identify a number of “monomer A-monomer B” pairs that rely on “knobs and holes”. In addition, as described in Merchant et al., Nature Biotech. 16:677 (1998), these “knobs and hole” mutations can be combined with disulfide bonds to skew formation to heterodimerization. 
     An additional mechanism that finds use in the generation of heterodimers is sometimes referred to as “electrostatic steering” as described in Gunasekaran et al., J. Biol. Chem. 285(25):19637 (2010), hereby incorporated by reference in its entirety. This is sometimes referred to herein as “charge pairs”. In this embodiment, electrostatics are used to skew the formation towards heterodimerization. As those in the art will appreciate, these may also have an effect on pI, and thus on purification, and thus could in some cases also be considered pI variants. However, as these were generated to force heterodimerization and were not used as purification tools, they are classified as “steric variants”. These include, but are not limited to, D221E/P228E/L368E paired with D221R/P228R/K409R (e.g., these are “monomer” corresponding sets) and C220E/P228E/368E paired with C220R/E224R/P228R/K409R. 
     Additional monomer A and monomer B variants can be combined with other variants, optionally and independently in any amount, such as pI variants outlined herein or other steric variants that are shown in FIG. 37 of US 2012/0149876, all of which are incorporated expressly by reference herein. 
     In some embodiments, the steric variants outlined herein can be optionally and independently incorporated with any pI variant (or other variants such as Fc variants, FcRn variants, etc.) into one or both monomers, and can be independently and optionally included or excluded from the proteins of the invention. 
     A list of suitable skew variants is found in  FIG. 5 . Of particular use in many embodiments are the pairs of sets including, but not limited to, S364K/E357Q:L368D/K370S; L368D/K370S:S364K; L368E/K370S:S364K; T411T/E360E/Q362E:D401K; L368D/K370S:S 364K/E357L; K370S:S364K/E357Q; and T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C). In terms of nomenclature, the pair “S364K/E357Q:L368D/K370S” means that one of the monomers has the double variant set S364K/E357Q and the other has the double variant set L368D/K370S; as above, the “strandedness” of these pairs depends on the starting pI. 
     C. pI (Isoelectric Point) Variants for Heterodimers 
     In general, as will be appreciated by those in the art, there are two general categories of pI variants: those that increase the pI of the protein (basic changes) and those that decrease the pI of the protein (acidic changes). As described herein, all combinations of these variants can be used: one monomer may be wild type, or a variant that does not display a significantly different pI from wild-type, and the other can be either more basic or more acidic. Alternatively, each monomer may be changed, one to more basic and one to more acidic. 
     Preferred combinations of pI variants are shown in FIG. 30 of U.S. Ser. No. 15/141,350, all of which are herein incorporated by reference in its entirety. As outlined herein and shown in the figures, these changes are shown relative to IgG1, but all isotypes can be altered this way, as well as isotype hybrids. In the case where the heavy chain constant domain is from IgG2-4, R133E and R133Q can also be used. 
     In one embodiment, a preferred combination of pI variants has one monomer comprising 208D/295E/384D/418E/421D variants (N208D/Q295E/N384D/Q418E/N421D when relative to human IgG1) if one of the Fc monomers includes a CH1 domain. In some instances, the second monomer comprising a positively charged domain linker, including (GKPGS) 4  (SEQ ID NO: 38). In some cases, the first monomer includes a CH1 domain, including position 208. Accordingly, in constructs that do not include a CH1 domain (for example for heterodimeric Fc fusion proteins that do not utilize a CH1 domain on one of the domains), a preferred negative pI variant Fc set includes 295E/384D/418E/421D variants (Q295E/N384D/Q418E/N421D when relative to human IgG1). 
     In some embodiments, mutations are made in the hinge of the Fc domain, including positions 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, and 230. Thus, pI mutations and particularly substitutions can be made in one or more of positions 216-230, with 1, 2, 3, 4 or 5 mutations finding use in the present invention. Again, all possible combinations are contemplated, alone or with other pI variants in other domains. 
     Specific substitutions that find use in lowering the pI of hinge domains include, but are not limited to, a deletion at position 221, a non-native valine or threonine at position 222, a deletion at position 223, a non-native glutamic acid at position 224, a deletion at position 225, a deletion at position 235 and a deletion or a non-native alanine at position 236. In some cases, only pI substitutions are done in the hinge domain, and in others, these substitution(s) are added to other pI variants in other domains in any combination. 
     In some embodiments, mutations can be made in the CH2 region, including positions 233, 234, 235, 236, 274, 296, 300, 309, 320, 322, 326, 327, 334 and 339. It should be noted that changes in 233-236 can be made to increase effector function (along with 327A) in the IgG2 backbone. Again, all possible combinations of these 14 positions can be made; e.g., a pI antibody may have 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 CH2 pI substitutions. 
     Specific substitutions that find use in lowering the pI of CH2 domains include, but are not limited to, a non-native glutamine or glutamic acid at position 274, a non-native phenylalanine at position 296, a non-native phenylalanine at position 300, a non-native valine at position 309, a non-native glutamic acid at position 320, a non-native glutamic acid at position 322, a non-native glutamic acid at position 326, a non-native glycine at position 327, a non-native glutamic acid at position 334, a non-native threonine at position 339, and all possible combinations within CH2 and with other domains. 
     In this embodiment, the mutations can be independently and optionally selected from position 355, 359, 362, 384, 389, 392, 397, 418, 419, 444 and 447. Specific substitutions that find use in lowering the pI of CH3 domains include, but are not limited to, a non-native glutamine or glutamic acid at position 355, a non-native serine at position 384, a non-native asparagine or glutamic acid at position 392, a non-native methionine at position 397, a non-native glutamic acid at position 419, a non-native glutamic acid at position 359, a non-native glutamic acid at position 362, a non-native glutamic acid at position 389, a non-native glutamic acid at position 418, a non-native glutamic acid at position 444, and a deletion or non-native aspartic acid at position 447. 
     D. Isotypic Variants 
     In addition, many embodiments of the invention rely on the “importation” of pI amino acids at particular positions from one IgG isotype into another, thus reducing or eliminating the possibility of unwanted immunogenicity being introduced into the variants. A number of these are shown in FIG. 21 of US Publ. App. No. 2014/0370013, hereby incorporated by reference. That is, IgG1 is a common isotype for therapeutic antibodies for a variety of reasons, including high effector function. However, the heavy constant region of IgG1 has a higher pI than that of IgG2 (8.10 versus 7.31). By introducing IgG2 residues at particular positions into the IgG1 backbone, the pI of the resulting monomer is lowered (or increased) and additionally exhibits longer serum half-life. For example, IgG1 has a glycine (pI 5.97) at position 137, and IgG2 has a glutamic acid (pI 3.22); importing the glutamic acid will affect the pI of the resulting protein. As is described below, a number of amino acid substitutions are generally required to significantly affect the pI of the variant Fc fusion protein. However, it should be noted as discussed below that even changes in IgG2 molecules allow for increased serum half-life. 
     In other embodiments, non-isotypic amino acid changes are made, either to reduce the overall charge state of the resulting protein (e.g., by changing a higher pI amino acid to a lower pI amino acid), or to allow accommodations in structure for stability, etc. as is more further described below. 
     In addition, by pI engineering both the heavy and light constant domains, significant changes in each monomer of the heterodimer can be seen. As discussed herein, having the pIs of the two monomers differ by at least 0.5 can allow separation by ion exchange chromatography or isoelectric focusing, or other methods sensitive to isoelectric point. 
     E. Calculating pI 
     The pI of each monomer can depend on the pI of the variant heavy chain constant domain and the pI of the total monomer, including the variant heavy chain constant domain and the fusion partner. Thus, in some embodiments, the change in pI is calculated on the basis of the variant heavy chain constant domain, using the chart in the FIG. 19 of US Publ. App. No. 2014/0370013. As discussed herein, which monomer to engineer is generally decided by the inherent pI of each monomer. 
     F. pI Variants that Also Confer Better FcRn In Vivo Binding 
     In the case where the pI variant decreases the pI of the monomer, they can have the added benefit of improving serum retention in vivo. 
     Although still under examination, Fc regions are believed to have longer half-lives in vivo, because binding to FcRn at pH 6 in an endosome sequesters the Fc (Ghetie and Ward, 1997 Immunol Today. 18(12): 592-598, entirely incorporated by reference). The endosomal compartment then recycles the Fc to the cell surface. Once the compartment opens to the extracellular space, the higher pH, ˜7.4, induces the release of Fc back into the blood. In mice, Dall&#39; Acqua et al. showed that Fc mutants with increased FcRn binding at pH 6 and pH 7.4 actually had reduced serum concentrations and the same half-life as wild-type Fc (Dall&#39; Acqua et al. 2002, J. Immunol. 169:5171-5180, entirely incorporated by reference). The increased affinity of Fc for FcRn at pH 7.4 is thought to forbid the release of the Fc back into the blood. Therefore, the Fc mutations that will increase Fc&#39;s half-life in vivo will ideally increase FcRn binding at the lower pH while still allowing release of Fc at higher pH. The amino acid histidine changes its charge state in the pH range of 6.0 to 7.4. Therefore, it is not surprising to find His residues at important positions in the Fc/FcRn complex. 
     G. Additional Fc Variants for Additional Functionality 
     In addition to pI amino acid variants, there are a number of useful Fc amino acid modification that can be made for a variety of reasons, including, but not limited to, altering binding to one or more FcγR, altered binding to FcRn, etc. 
     Accordingly, the proteins of the invention can include amino acid modifications, including the heterodimerization variants outlined herein, which includes the pI variants and steric variants. Each set of variants can be independently and optionally included or excluded from any particular heterodimeric protein. 
     H. FcγR Variants 
     Accordingly, there are a number of useful Fc substitutions that can be made to alter binding to one or more of the Fcγ receptors. Substitutions that result in increased binding as well as decreased binding can be useful. For example, it is known that increased binding to FcγRIIIa results in increased ADCC (antibody dependent cell-mediated cytotoxicity; the cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause lysis of the target cell). Similarly, decreased binding to FcγRIIb (an inhibitory receptor) can be beneficial as well in some circumstances. Amino acid substitutions that find use in the present invention include those listed in U.S. Ser. No. 11/124,620 (particularly  FIG. 41 ), U.S. Ser. Nos. 11/174,287, 11/396,495, 11/538,406, all of which are expressly incorporated herein by reference in their entirety and specifically for the variants disclosed therein. Particular variants that find use include, but are not limited to, 236A, 239D, 239E, 332E, 332D, 239D/332E, 267D, 267E, 328F, 267E/328F, 236A/332E, 239D/332E/330Y, 239D, 332E/330L, 243A, 243L, 264A, 264V and 299T. 
     In addition, amino acid substitutions that increase affinity for FcγRIIc can also be included in the Fc domain variants outlined herein. The substitutions described in, for example, U.S. Ser. Nos. 11/124,620 and 14/578,305 are useful. 
     In addition, there are additional Fc substitutions that find use in increased binding to the FcRn and increased serum half-life, as specifically disclosed in U.S. Ser. No. 12/341,769, hereby incorporated by reference in its entirety, including, but not limited to, 434S, 434A, 428L, 308F, 259I, 428L/434S, 259I/308F, 436I/428L, 436I or V/ 434S, 436V/428L and 259I/308F/428L. 
     I. Ablation Variants 
     Similarly, another category of functional variants are “FcγR ablation variants” or “Fc knock out (FcKO or KO)” variants. In these embodiments, for some therapeutic applications, it is desirable to reduce or remove the normal binding of the Fc domain to one or more or all of the Fcγ receptors (e.g., FcγR1, FcγRIIa, FcγRIIb, FcγRIIIa, etc.) to avoid additional mechanisms of action. That is, for example, in many embodiments, particularly in the use of immunomodulatory proteins, it is desirable to ablate FcγRIIIa binding to eliminate or significantly reduce ADCC activity such that one of the Fc domains comprises one or more Fcγ receptor ablation variants. These ablation variants are depicted in FIG. 31 of U.S. Ser. No. 15/141,350, all of which are herein incorporated by reference in its entirety, and each can be independently and optionally included or excluded, with preferred aspects utilizing ablation variants selected from the group consisting of G236R/L328R, E233P/L234V/L235A/G236del/S239K, E233P/L234V/L235A/G236del/S267K, E233P/L234V/L235A/G236del/S239K/A327G, E233P/L234V/L235A/G236del/S267K/A327G and E233P/L234V/L235A/G236del, according to the EU index. In addition, ablation variants of use in the present invention are also depicted in  FIG. 7 . It should be noted that the ablation variants referenced herein ablate FcγR binding but generally not FcRn binding. 
     J. Combination of Heterodimeric and Fc Variants 
     As will be appreciated by those in the art, all of the recited heterodimerization variants (including skew and/or pI variants) can be optionally and independently combined in any way, as long as they retain their “strandedness” or “monomer partition”. In addition, all of these variants can be combined into any of the heterodimerization formats. 
     In the case of pI variants, while embodiments finding particular use are shown in the Figures, other combinations can be generated, following the basic rule of altering the pI difference between two monomers to facilitate purification. 
     In addition, any of the heterodimerization variants, skew and pI, may also be independently and optionally combined with Fc ablation variants, Fc variants, FcRn variants, as generally outlined herein. 
     In addition, a monomeric Fc domain can comprise a set of amino acid substitutions that includes C220S/S267K/L368D/K370S or C220S/S267K/S364K/E357Q. 
     In addition, the heterodimeric Fc fusion proteins can comprise skew variants (e.g., a set of amino acid substitutions as shown in FIGS. 1A-1C of U.S. Ser. No. 15/141,350, all of which are herein incorporated by reference in its entirety), with particularly useful skew variants being selected from the group consisting of S364K/E357Q:L368D/K370S; L368D/K370S:S364K; L368E/K370S:S364K; T411T/E360E/Q362E:D401K; L368D/K370S:S364K/E357L; K370S:S 364K/E357Q; T366S/L368A/Y407V:T366W; and T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C), optionally ablation variants, optionally charged domain linkers; and optionally pI variants. 
     In some embodiments, the Fc domain comprises one or more amino acid substitutions selected from the group consisting of: 236R, S239D, S239E, F243L, M252Y, V259I, S267D, S267E, S67K, S298A, V308F, L328F, L328R, 330L, I332D, 1332E, M428L, N434A, N434S, 236R/L328R, S239D/I332E, 236R/L328F, V259I/V308F, S267E/L328F, M428L/N43S, Y436I/M428L, N436V/M428L, V436I/N434S, Y436V/N434S, S239D/1332E/330L, M252Y/S54T/T256E, V2591/V308F/M428L, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K according to EU index. 
     In one embodiment, a particular combination of skew and pI variants that finds use in the present invention is T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C) with one monomer comprising Q295E/N384D/Q418E/N481D and the other a positively charged domain linker. As will be appreciated in the art, the “knobs in holes” variants do not change pI, and thus can be used on either monomer. 
     In a further embodiment, the heterodimers of the present invention include a combination of heterodimeric and Fc domain variants such as those depicted in the figures. 
     In some embodiments, exemplary CH1 and partial hinge regions are used to covalently link a variable domain to the Fc backbones for targeted IL-10 fusion proteins of the present invention. Such sequences are provided in  FIG. 12  and the sequence listing for the corresponding SEQ ID NOS. 
     In some embodiments, the Fc domains of any of the untargeted and targeted IL-10 fusion proteins provided herein comprise modifications promoting heterodimerization of Fc domains. In some embodiments, the modifications promoting heterodimerization are a set of amino acid substitutions selected from the group consisting of L368D/K370S and S364K; L368D/K370S and S364K/E357L; L368D/K370S and S364K/E357Q; T411E/K360E/Q362E and D401K; L368E/K370S and S364K; K370S and S364K/E357Q and T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C), according to EU numbering. In some embodiments, the Fc domains have an additional set of amino acid substitutions comprising Q295E/N384D/Q418E/N421D, according to EU numbering. In some embodiments, the Fc domains have an additional set of amino acid substitutions consisting of G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. In some embodiments, the Fc domain comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. Additional modifications are provided in the figures include  FIGS. 5A-11C . 
     III. Interleukin 10 
     The present invention relates to the biologically functional form of interleukin 10. As stated above, the biologically functional form of interleukin 10 (or “IL-10” or “IL10”) is a domain-swapped homodimer formed by non-covalent interactions between two IL-10 monomers (also referred to herein as “IL-10 monomer domains”). The biologically functional IL-10 dimer binds the IL-10 receptor which consists of two alpha and two beta subunits (or R1 and R2 subunits). Notably, the IL-10 dimer becomes biologically inactive upon disruption of the interaction between the individual IL-10 monomers. Different formats of IL-10 monomer domains can be used in accordance with the Fc fusion proteins described in further detail herein. Some exemplary formats are pictured in  FIG. 14 . Each monomer may contain two domains: (i) the (A-D) domain ( FIG. 14A ), which comprises residues 1-116 of the mature form of the human IL-10 protein, and (ii) the (E-F) domain ( FIG. 14B ), which comprises residues 117-160-of the mature form of the human IL-10 protein. As discussed above, the biologically active IL-10 comprises a domain swapped homodimer, which is schematically illustrated in  FIG. 14C . Another format of use in the present invention is a single-chain IL-10 complex or “scIL-10” comprising a first IL-10 monomer covalently attached to a second IL-10 monomer, optionally via a linker (see  FIG. 14D ). Another format of IL-10 of use in the present invention is illustrated in  FIG. 14E , which depicts the monomeric IL-10 or “IL10M1” described in for example Josephson et al. (2000), which is hereby incorporated by reference in its entirety and in particular for all teachings related to IL10M1, which is generated by engineering a domain linker between hIL-10(A-D) (e.g., the A-D domain of an IL-10 monomer) and hIL-10(E-F) (e.g., the E-F domain of an IL-10 monomer). Another format of IL-10 of use in the present invention is a split IL-10 format that comprises an hIL-10(A-D) domain non-covalently attached to an hIL-10(E-F) domain, as depicted in  FIG. 14F . 
     In some embodiments, the human IL-10 protein has the amino acid sequence set forth in NCBI Ref. Seq. No. NP_000563.1, SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO:4 (human IL-10 (109L) mature form sequence), all as depicted in  FIG. 1 . As will be appreciated, the IL-10 proteins of use in the present invention may include a histidine at position 109 (109H) or in other embodiments a leucine at position 109 (109L). In some embodiments, the IL-10 monomer domain sequence has at least at least 90%, e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more sequence identity to SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO:4 (human IL-10 (109L) mature form sequence), all as depicted in  FIG. 1 . The IL-10 monomer domain of the Fc fusion protein can further have 1, 2, 3, 4, 5, 6, 7, 8 or 9 amino acid mutations in the amino acid sequences depicted in  FIG. 1 . Further exemplary sequences for IL-10 components and configurations of use in the present invention are provided in the figures including FIGS.  15 A- 15 D,  21 A- 21 C,  22 ,  35 A- 35 D,  36 A- 36 E,  39 A- 39 G,  40 A- 40 M,  41 A- 41 F,  48 ,  49 A- 49 B,  53 ,  55 ,  56 A- 56 C,  57 ,  58 ,  59 A- 59 H,  60 ,  64 ,  65 A- 65 B,  66 A- 66 D,  67 ,  68 ,  69 ,  70 A- 70 B,  71 A- 71 E,  73 ,  4 A- 74 B,  75 A- 75 B,  76 A- 76 D,  78 A- 78 G,  79 A- 79 G, and  86 A- 86 D, and in the sequence listing for the corresponding sequence identifiers. 
     The present invention also provides variant IL-10 monomer domains. These variants find use as part of the biologically functional IL-10 complex as well as any of the IL-10-Fc fusions described herein. 
     A. Expression Variants 
     The IL-10 monomer domains subunits of the invention can in some embodiments include variants to improve/increase expression, particularly for the heterodimer formats. Such variants may include variants that reduce or remove potential for deamidation, reduce or remove potential for aspartic acid isomerization, reduce or remove potential for degradation-related PTMs, reduce or remove potential degradation sites, reduce/remove disulfide bridges, and/or reduce or remove potential N-glycosylation sites. Exemplary sequences for IL-10 components and expression variants of use in the present invention are provided in the figures including  FIGS. 15A-15D, 21A-21C, 22, 35A-35D, 36A-36E, 39A-39G, 40A-40M, 41A-41F, 48, 49A-49B, 53, 55, 56A - 56 C,  57 ,  58 ,  59 A- 59 H,  60 ,  64 ,  65 A- 65 B,  66 A- 66 D,  67 ,  68 ,  69 ,  70 A- 70 B,  71 A- 71 E,  73 ,  4 A- 74 B,  75 A- 75 B,  76 A- 76 D,  78 A- 78 G,  79 A- 79 G, and  86 A- 86 D, and in the sequence listing for the corresponding sequence identifiers. 
     As will be appreciated, different formats of the IL-10 Fc fusion proteins of the invention will contain different amino acid modifications and combinations of amino acid modifications to fulfill the above described functions and thereby improve/increase expression of proteins of the invention. Exemplary embodiments of different variant sequences for different formats of Fc fusion proteins of the invention are depicted in  FIGS. 15A-15D, 21A-21C, 22, 35A-35D, 36A-36E, 39A-39G, 40A-40M, 41A-41F, 48, 49A-49B, 53, 55, 56A - 56 C,  57 ,  58 ,  59 A- 59 H,  60 ,  64 ,  65 A- 65 B,  66 A- 66 D,  67 ,  68 ,  69 ,  70 A- 70 B,  71 A- 71 E,  73 ,  4 A- 74 B,  75 A- 75 B,  76 A- 76 D,  78 A- 78 G,  79 A- 79 G, and  86 A- 86 D, and in the sequence listing for the corresponding sequence identifiers. 
     B. Affinity Variants 
     The invention provides IL-10 variants which form biologically functional IL-10 with altered, that is either reduced or increased, binding affinity for IL-10 receptors. Such variants may also or instead show altered (reduced or increased) potency. 
     Suitable sites on IL-10 at which amino acid modifications can be introduced include N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, and E151 (numbered according to the human IL-10 (IL-10 mature form sequence as depicted in  FIG. 1 , with either the 109H or 109L sequence). Illustrative modifications at these sites include N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, and E151Q. In some embodiments, the IL-10 variants comprise one or more substitutions selected from the group consisting of N21, D28, Q38, D41, D44, Q42, N45, E142, D144, and E151 (numbered according to human IL-10 mature form sequence, as depicted in  FIG. 1 ). In some embodiments, the IL-10 variants comprise one or more substitutions selected from the group consisting of N21D, D28N, Q38E, D41N, Q42E, D44N, N45D, E142Q, D144N, and E151Q (numbered according to human IL-10 mature form sequence, as depicted in  FIG. 1 ). In some embodiments, the IL-10 variants further comprise one or more substitutions selected from the group consisting of M39, L43, and 187. In some instances, the substitutions include M39T, L43V, I87A, and any combination thereof. IL-10 affinity/potency variants can include modifications at one or more of these sites. In further embodiments, one or more amino acid modifications for altering affinity and/or potency can be combined with one or more additional modifications, including expression variants. These modifications can be used alone or in combination with any other IL-10 variants, such as variants to modulate affinity/potency, introduce/remove disulfide bridges, improve yield, remove charge variants, remove glycosylation sites, and/or improve stability. 
     Exemplary combinations of affinity/potency variants of use in the present invention include Q38E/D41N, Q38E/Q42E, Q38E/N45D, Q38E/E142Q, Q38E/D144N, D41N/Q42E, D41N/N45D, D41N/E142Q, D41N/D144N, Q42E/N45D, Q42E/E142Q, Q42E/D144N, N45D/E142Q, N45D/D144N, E142Q/D144N, N21D/Q42E, N21D/N45D, N21D/E151Q, N21D/N45E, Q42E/E151Q, N45D/E151Q, N21D/Q42E/N45D, N21D/Q42E/E151Q, Q42E/N45D/E151Q, N21D/Q42E/N45E, and N21D/Q42E/N45D/E151Q. 
     In some embodiments, the IL-10 variant of any of the formats of the present invention comprises any of the following substitutions selected from the group consisting of Q38E/Q198E, D41N/D201N, Q42E/Q202E, N45D/N205D, E142Q/E302Q, E142Q/E302Q, D144N/D304N, Q38E/D41N/Q198E/D201N, Q38E/Q42E/Q198E/Q202E, Q38E/N45D/Q198E/N205D, Q38E/E142Q/Q198E/E302Q, Q38E/D144N/Q198E/D304N, D41N/Q42E/D201N/Q202E, D41N/N45D/D201N/N205D, D41N/E142Q/D201N/E302Q, D41N/D144N/D201N/D304N, Q42E/N45D/Q202E/N205D, Q42E/E142Q/Q202E/E302Q, Q42E/D144N/Q202E/D304N, N45D/E142Q/N205D/E302Q, N45D/D144N/N205D/D304N, E142Q/D144N/E302Q/D304N, N21D/N181D, E151Q/E311Q, N21D/Q42E/N181D/Q202E, N21D/N45D/N181D/N205E, N21D/N45D/N181D/N205D, N21D/E151Q/N181D/E311Q, Q42E/E151Q/E311Q, N45D/E151Q/N205D/E311Q, N21D/Q42E/N45D/N181D/Q202E/N205E, N21D/Q42E/E151Q/N181D/Q202E/E311Q, Q42E/N45D/E151Q/Q202E/N205D/E311Q, N21D/Q42E/N45D/E151Q/N181D/Q202E/N205D/E311Q, Q38E/N45D/N205D, D41N/N45D/N205D, N45D/D144N/N205D, N205D, N45D, N21D/N45D/N205D, N45D/N181D/N205D, N45D/E151Q/N205D, N45D/N205D/E311Q, and N45D/N205D/D304N. 
     In some embodiments, the IL-10 variant of any of the formats of the present invention comprises any of the following substitutions selected from the group consisting of N10A, N10Q, N92A, N126A, N160A, N10A/N45D/N170A/N205D, N45D/N92A/N205D/N252A, N45D/N126A/N205D/N286A, N45D/N160A/N205D, N45D/N205D/N320A, N45D/N160A/N205D/N320A, N10A/N45D/N170A/N205D/N320A, N10A/N45D/N170A/N205D/N320_, N10A/N45D/N170A/N205D/R319_/N320_, N10A/N45D/N170A/N205D/I318_/R319_/N320_, N10A/N45D/N170A/N205D/K317_/I318_/R319_/N320_, N10A/N45D/N205D/N320A, N45D/N170A/N205D/N320A, N10Q/N45D/N170Q/N205D/N320A, D28A, and D28A/N45D/D188A/N205D. In some embodiments, the scIL10 variant comprises any of the following substitutions selected from the group consisting of N10A, N92A, N126A, N160A, N170A, N170Q, N252A, N286A, N320A, K317_, I318_, R319_, N320_, and any combination thereof. In some embodiments, the substitution(s) reduces the potential for deamidation of the fusion protein. 
     In some embodiments, the IL-10 variant of any of the formats of the present invention comprises any of the following substitutions selected from the group consisting of D28A and D28A/N45D/D188A/N205D. In some embodiments, the substitution(s) reduces the potential for aspartic acid isomerization. 
     In some embodiments, the IL-10 variant of any of the formats of the present invention comprises any of the following substitutions selected from the group consisting of N116D, N116Q, K117P, S118A, N45D/N116D/N205D, N45D/N116D/N205D, N45D/K117P/N205D, N45D/S118A/N205D, N45D/N205D/N276D, N45D/N205D/N276Q, N45D/N205D/K277P, N45D/N205D/S178A, and N45D/N116D/N205D/N276D. In some embodiments, the substitution reduces N-glycosylation sites. 
     In some embodiments, the IL-10 variant of any of the formats of the present invention comprises any of the following substitutions selected from the group consisting of C12A/C108A and C12A/N45D/C108A/C172A/N205D/C268A/N320A. In some embodiments, the substitution(s) reduces the potential for the formation of disulfide bridges. 
     In some embodiments, the IL-10 variant of any of the formats of the present invention comprises any of the following substitutions selected from the group consisting F37C/M140C, Q38C/S141C, D41C/K138C, L47C/K138C, L48C/E142C, S51C/A120C, D55C/A120C, F56C/Y153C, C62A/C114A, A64C/S118C, M68C/V121C, and V76C/A139C. In some embodiments, the IL10M1 variant comprises one or more cysteine substitution(s) at the following residues: F37, Q38, D41, L47, L48, S51, D55, F56, A64, M68, and V76 in helices A-D; and S118, A120, V121, K138, A139, M140, S141, E142, and Y153 in helices E-F. In some instances, disulfide bridges between the following amino acid pairs is found in an IL10M1 variants: F37C:M140C, Q38C:S141C, D41C:K 138C, L47C:K138C, L48C: E142C, S51C: A120C, D55C: A120C, F56C: Y153C, A64C:S118C, M68C: V121C, and V76C: A139C to promote stabilization of the interaction between helices A-D and helices E-F. In some embodiments, the substitution(s) allows for the formation of disulfide bridges. 
     In some embodiments, the IL-10 variant of any of the formats of the present invention comprises any of the following substitutions selected from the group consisting L47Q, S118A, and A139Q. In some embodiments, the IL-10 variant of any of the formats comprises any of the following substitutions selected from the group consisting L19, L23, L26, A29, F30, V33, F37, L47, L48, L52, F56, A64, L65, S66, M68, 169, F71, Y72, V76, M77, A80, E81, 187, V91, L94, G95, L98, L101, L105, L112, S118, V121, V124, F128, K138, A139, M140, S141, F143, F146, 1147, and 1150. 
     Exemplary sequences for IL-10 components and affinity variants of use in the present invention are provided in the figures including  FIGS. 15A-15D, 21A-21C, 22, 35A-35D, 36A-36E, 39A-39G, 40A-40M, 41A-41F, 48, 49A-49B, 53, 55, 56A - 56 C,  57 ,  58 ,  59 A- 59 H,  60 ,  64 ,  65 A- 65 B,  66 A- 66 D,  67 ,  68 ,  69 ,  70 A- 70 B,  71 A- 71 E,  73 ,  4 A- 74 B,  75 A- 75 B,  76 A- 76 D,  78 A- 78 G,  79 A- 79 G, and  86 A- 86 D, and in the sequence listing for the corresponding sequence identifiers. 
     A biologically functional IL-10 dimer can comprise two wild-type IL-10 monomers or a variant IL-10 monomer and a wild-type IL-10 monomer. 
     IV. Antigen Binding Domains 
     As is discussed below, the term “antibody” or “antigen binding domain” is used generally. Antigen binding domains that find use in the present invention can take on a number of formats as described herein, including traditional antibodies as well as antibody derivatives, fragments and mimetics, described herein and depicted in the Figures. In some embodiments, the present invention provides antibody fusion proteins containing a checkpoint antigen binding domain and an Fc domain. In some embodiments, the present invention provides antibody fusion proteins containing an immune cell antigen binding domain and an Fc domain. 
     Traditional antibody structural units typically comprise a tetramer. Each tetramer is typically composed of two identical pairs of polypeptide chains, each pair having one “light” (typically having a molecular weight of about 25 kDa) and one “heavy” chain (typically having a molecular weight of about 50-70 kDa). Human light chains are classified as kappa and lambda light chains. The present invention is directed to antibodies or antibody fragments (antibody monomers) that generally are based on the IgG class, which has several subclasses, including, but not limited to IgG1, IgG2, IgG3, and IgG4. In general, IgG1, IgG2 and IgG4 are used more frequently than IgG3. It should be noted that IgG1 has different allotypes with polymorphisms at 356 (D or E) and 358 (L or M). The sequences depicted herein use the 356D/358M allotype, however the other allotype is included herein. That is, any sequence inclusive of an IgG1 Fc domain included herein can have 356E/358L replacing the 356D/358M allotype. 
     In addition, many of the sequences herein have at least one the cysteines at position 220 replaced by a serine; generally this is the on the “scFv monomer” side for most of the sequences depicted herein, although it can also be on the “Fab monomer” side, or both, to reduce disulfide formation. Specifically included within the sequences herein are one or both of these cysteines replaced (C220S). 
     The PD-1 antigen binding domain (ABD) (e.g., the anti-PD-1 component) of the targeted IL-10 Fc fusion protein is generally a set of 6 CDRs and/or a variable heavy domain and a variable light domain that form an Fv domain that can bind human PD-1. As shown herein, the anti-PD-1 ABD can be in the form of a scFv, wherein the vh and vl domains are joined using an scFv linker, which can be optionally a charged scFv linker. As will be appreciated by those in the art, the scFv can be assembled from N- to C-terminus as N-vh-scFv linker-vl-C or as N-vl-scFv linker-vh-C, with the C terminus of the scFv domain generally being linked to the hinge-CH2-CH3 Fc domain. Suitable Fvs (including CDR sets and variable heavy/variable light domains) can be used in scFv formats or Fab formats are shown in the Figures as well as disclosed in WO2017/218707 and PCT/US2018/059887 filed Nov. 8, 2018, hereby expressly incorporated in their entirety, and specifically for Figures, Legends, and SEQ identifiers that depict anti-PD-1 sequences. 
     In some embodiments, PD-1 ABDs are based on the 1C11 clone, shown in the Figures. In some embodiments, PD-1 ABDs of the present invention are based on a variant heavy chain based on the heavy chain of 1C11 clone shown in  FIGS. 100A-100B  and a variant light chain based on the light chain of 1C11 clone shown in  FIGS. 100A-100B . In some embodiments, a PD-1 ABD comprises a variant heavy chain and light chain pair selected from the group consisting of one depicted in  FIGS. 100A-100G  and the corresponding SEQ ID NOS including 1C11[PD-1]_H0L0, 1C11[PD-1]_H3L3, 1C11[PD-1]_H3.240_L3.148, 1C11[PD-1]_H3.241_L3.148, 1C11[PD- 1]_H3.234_L3.144, 1C11[PD-1]_H3.241_L3.92, 1C11[PD-1]_H3.303_L3.152, 1C11_H3.329_L3.220, 1C11_H3.328_L3.152, pembrolizumab VH and VL chains, nivolumab VH and VL chains, pidilizumab VH and VL chains, MK-3475 VH and VL chains, BAP049 Clone E VH and VL chains, BAP049 Clone B VH and VL chains, H7798N VH and VL chains, h1H3 Var 6 VH and VL chains, APE2058 VH and VL chains, H005-1 VH and VL chains, 317-4B6, 326-4A3 VH and VL chains, hPD-1 mAb 7 (1.2) VH and VL chains, Clone 38[PD-1] VH and VL chains, Clone 39[PD-1] VH and VL chains, Clone 41[PD-1] VH and VL chains, Clone 48[PD-1] VH and VL chains, PD1-17[PD-1] VH and VL chains, PD1-28[PD-1] VH and VL chains, PD1-33[PD-1] VH and VL chains, PD1-35[PD-1] VH and VL chains, LOPD180[PD-1] VH and VL chains, Ab948[PD-1] VH and VL chains, humanized EH-12.2H7 VH and VL chains, RG1H10 VH and VL chains, RG1H10-H2A-22-1S VH and VL chains, RG1H10-H2A-27-25 VH and VL chains, RG1H10-3C VH and VL chains, RG1H10-16C VH and VL chains, RG1H10-17C VH and VL chains, RG1H10-19C VH and VL chains, RG1H10-21C VH and VL chains, RG1H10-23C2 VH and VL chains, mAb7[PD-1] VH and VL chains, and PD1AB-6[PD-1] VH and VL chains. As will be appreciated by those in the art, the VH and VL domains can be formatted as, Fab or scFvs for use in the PD-1-targeted IL-10 fusion proteins of the invention. 
     In some embodiments, non-competing PD-1 ABDs are based on the mAb A, mAb B, and mAb C clones, shown in the Figures. In some embodiments, non-competing PD-1 ABDs of the present invention are based on a variant heavy chain based on the heavy chain of the mAb A, mAb B, or mAb C clone shown in  FIGS. 104A-104B  and a variant light chain based on the light chain of the mAb A, mAb B, or mAb C clone shown in  FIGS. 104A-104B . In some embodiments, a non-competing PD-1 ABD comprises a variant heavy chain and light chain pair selected from the group consisting of one depicted in  FIGS. 104A-104B  and the corresponding SEQ ID NOS including mAb A[PD-1]_H1_11 and mAb B[PD-1]_H1_L1. 
     In some embodiments, a non-competing PD-1 ABD comprises a variant heavy chain selected from the group consisting of mAb C[PD-1]_H1, mAb C[PD-1]_H1.19, mAb C[PD-1]_H1.48, mAb C[PD-1]_H1.125, mAb C[PD-1]_H1.130, mAb C[PD-1]_H1.132, mAb C[PD-1]_H1.169, mAb C[PD-1]_H1.175, and mAb C[PD-1]_H2, and a variant light chain selected from the group consisting of mAb C[PD-1]_11, mAb C[PD-1]_L1.1, mAb C[PD-1]_L1.3, mAb C[PD-1]_L1.45, mAb C[PD-1]_L1.117, mAb C[PD-1]_L1.129, mAb C[PD-1]_L1.135, mAb C[PD-1]_L1.136, mAb C[PD-1]_L1.140, and mAb C[PD-1]_L2. As will be appreciated by those in the art, the VH and VL domains can be formatted as Fab or scFvs for use in the targeted IL-10 fusion proteins of the invention. 
     In some embodiments, a TIGIT ABD comprises a variant heavy chain selected from the group consisting of 2A5B4[TIGIT]_H1_L1, 4.1 D3.Q1E(tiragolumab)[TIGIT]_H0_L0, 10A7[TIGIT] VH and VL chains, 1F4[TIGIT], and 4.1D3[TIGIT] VH and VL chains. As will be appreciated by those in the art, the VH and VL domains can be formatted as Fab or scFvs for use in the targeted IL-10 fusion proteins of the invention. 
     In some embodiments, a TIGIT ABD comprises a variant heavy chain selected from the group consisting of Hu14D7 VH1, Hu14D7 VH2, and Hu14D7 VH3, and a variant light chain selected from the group consisting of Hu14D7 VL1, Hu14D7 VL2, and Hu14D7 VL3. As will be appreciated by those in the art, the VH and VL domains can be formatted as Fab or scFvs for use in the targeted IL-10 fusion proteins of the invention. 
     In some embodiments, a TIGIT ABD comprises a variant heavy chain selected from the group consisting of Hu26B10 VH1, Hu26B10 VH2, and Hu26B10 VH3, and a variant light chain selected from the group consisting of Hu26B10 VL1, Hu26B10 VL2, and Hu26B10 VL3. As will be appreciated by those in the art, the VH and VL domains can be formatted as Fab or scFvs for use in the targeted IL-10 fusion proteins of the invention. 
     In some embodiments, a TIGIT ABD comprises a variant heavy chain and light chain pair selected from the group consisting of MEB125.31C6.A1.205 VH4/VL1, MEB125.31C6.A1.205 VH5/VL4, MEB125.31C6.A1.205 VH5/VL3, 15A6 VH and VL chains, 22G2A6 VH and VL chains, 11G11 VH and VL chains, 10D7 VH and VL chains, 10D7 VH and VL chains, 313R19 VH and VL chains, and etigilimab VH and VL chains. As will be appreciated by those in the art, the VH and VL domains can be formatted as Fab or scFvs for use in the targeted IL-10 fusion proteins of the invention. 
     In some embodiments, an NKG2D ABD comprises a variant heavy chain and light chain pair selected from the group consisting of MS[NKG2D] H0_L0, 1D7B4[NKG2D]_H1_L1, KYK-1.0[NKG2D]_H1_L1, KYK-2.0[NKG2D]_H0_L0, 11B2D10[NKG2D]_H0_L0, 6E5A7[NKG2D]_H0_L0, 6H7E7[NKG2D]_H0_L0, mAb E[NKG2D]_H1_L1, 16F31[NKG2D]_H1_L1, mAb D[NKG2D]_H1_L1, 1 D7B4[NKG2D]_H1_L1, mAb A[NKG2D]_H1_L1, mAb A[NKG2D]_H1_L2, mAb A[NKG2D]_H2_L1, mAb A[NKG2D]_H2_L2, mAb B[NKG2D]_H1_L1, mAb B[NKG2D]_H1_L1.1, mAb B[NKG2D]_H1_L2, mAb B[NKG2D]_H2_L1, mAb B[NKG2D]_H2_L1.1, mAb B[NKG2D]_H2_L2, mAb B[NKG2D]_H3_L1, mAb B[NKG2D]_H3_L1.1, mAb B[NKG2D]_H3_L2, mAb C[NKG2D]_H1_L1, mAb C[NKG2D]_H1_L2, mAb C[NKG2D]_H2_L1, and mAb C[NKG2D]_H2_L2. As will be appreciated by those in the art, the VH and VL domains can be formatted as Fab or scFvs for use in targeted IL-10 fusion proteins of the invention. 
     In some embodiments, a CD8 ABD comprises a variant heavy chain and light chain pair selected from the group consisting of OKT8_H2_L1 and 1C11B3[CD8]_H1_L1. As will be appreciated by those in the art, the VH and VL domains can be formatted as Fab or scFvs for use in the targeted IL-10 fusion proteins of the invention. 
     V. Domain Linkers 
     In some embodiments, IL-10 monomers and/or IL-10 monomer helix domain (e.g., helices (A-D) and (E-F) are attached together via a linker. Optionally, the monomers and/or monomer helix domain are not attached via a linker. In other embodiments, IL-10 monomers or helix domain are noncovalently attached. In some embodiments, the IL-10 monomer and/or IL-10 monomer helix domain is attached to an Fc domain via a linker. In certain embodiments, IL-10 monomer and/or helix domain is attached to an Fc domain directly, such as without a linker. In some cases, a linker is not used to attach an IL-10 monomer or an IL-10 monomer helix domain to an Fc domain. 
     In some embodiments, the linker is a “domain linker”, used to link any two domains as outlined herein together. While any suitable linker can be used, many embodiments utilize a glycine-serine polymer, including for example (GS) n  (SEQ ID NO: 34), (GSGGS) n  (SEQ ID NO: 35), (GGGGS) n  (SEQ ID NO: 36), and (GGGS) n  (SEQ ID NO: 37), where n is an integer of at least 0 (and generally from 0 to 1 to 2 to 3 to 4 to 5), as well as any peptide sequence that allows for recombinant attachment of the two domains with sufficient length and flexibility to allow each domain to retain its biological function. In certain cases, useful linkers include (GGGGS) 0  (“GGGGS” disclosed as SEQ ID NO: 31) or (GGGGS) 1  (SEQ ID NO: 31) or (GGGGS) 2  (SEQ ID NO: 32). Illustrative domain linkers are depicted in  FIG. 103 . In some cases, and with attention being paid to “strandedness”, as outlined below, charged domain linkers can be used as discussed herein. 
     VI. Useful Untargeted Formats of the Invention 
     As shown in  FIGS. 16, 20, 23, and 29 , there are a number of useful formats of the untargeted IL-10 fusion proteins of the invention. In general, the fusion proteins of the invention have two functional components: an IL-10 dimer component and an Fc component, both of which can take different forms as outlined herein and each of which can be combined with the other component in any configuration. As shown in  FIGS. 87, 88, 89, and 90 , there are a number of useful formats of the targeted IL-10 fusion proteins of the invention. In general, the fusion proteins of the invention have two functional components: an IL-10 component, an Fc component, and an antigen binding domain, all of which can take different forms as outlined herein and each of which can be combined with the other component in any configuration. As will be appreciated, the IL-10 component in any of the formats described herein may comprise an IL-10 with a histidine at position 109 or a leucine at position 109. The IL-10 component may further include any of the IL-10 monomer variants described herein and known in the art. 
     In some embodiments, the IL-10 monomers are covalently linked, optionally with a domain linker, and referred to herein as a single-chain IL-10 complex or “scIL-10”. 
     In some embodiments, the IL-10 monomers are not covalently linked, but rather are covalently attached respectively to a first and a second Fc domain which are assembled as a dimer. 
     In some embodiments, different helices of the IL-10 monomer are attached to each other or to a first and a second Fc domain. In further embodiments, helices (A-D) of an IL-10 monomer are covalently linked to helices (E-F) in a single chain, optionally through a domain linker. In other embodiments, helices (A-D) are covalently attached to a first Fc domain (optionally through a domain linker) and helices (E-F) are covalently attached to a second Fc domain (optionally through a domain linker), such that when the first and second Fc domain associate, the (A-D) helices interact noncovalently with the (E-F) helices. As will be appreciated, in some embodiments, the first and second Fc domains are identical, and in some embodiments the first and second Fc domains are not identical. 
     The first and/or second Fc domains may have deletions in the Fc region to help enhance manufacturability. In some embodiments, such deletions may include without limitation G446del/K447del. 
     The first and the second Fc domains can have a set of amino acid substitutions selected from the group consisting of a) L368D/K370S and S364K; b) L368D/K370S and S364K/E357L; c) L368D/K370S and S364K/E357Q; d) T411E/K360E/Q362E and D401K; e) L368E/K370S and S364K; f) K370S and S364K/E357Q; and g) T366S/L368A/Y407V:T366W (optionally including a bridging disulfide, T366S/L368A/Y407V/Y349C:T366W/S354C), according to EU numbering. 
     In some embodiments, the first and/or the second Fc domains have an additional set of amino acid substitutions comprising Q295E/N384D/Q418E/N421D, according to EU numbering. 
     Optionally, the first and/or the second Fc domains have an additional set of amino acid substitutions consisting of G236R/L328R, E233P/L234V/L235A/G236_/S239K, E233P/L234V/L235A/G236_/S239K/A327G, E233P/L234V/L235A/G236_/S267K/A327G, E233P/L234V/L235A/G236_, and E233P/L234V/L235A/G236_/S267K, according to EU numbering. 
     Optionally, the first and/or second Fc domains have 428L/434S variants for half life extension. 
     As will be appreciated, any of the amino acid substitutions discussed herein, including any of the afore-described substitutions, may be used in any combination with the G445del/K447del modification. 
     In further preferred embodiments, the formats described herein contain antigen binding domains, where those antigen binding domains target IL-15. In still further embodiments, the antigen binding domains are non-competing PD-1 binding domains. 
     A. IL10-Fc Fusion Format 
     Towards engineering an IL-10 fusion protein wherein the IL-10 homodimer is pre-complexed, one embodiment comprises the IL10-Fc fusion format (cartoon schematics depicted in  FIG. 16 ). One such format of this category is the (IL10) 2 -Fc format (cartoon schematic depicted in  FIG. 16A ) which comprises two identical monomers, each monomer comprising an IL-10 monomer covalently attached to the N-terminus of a homodimeric Fc chain. Illustrative proteins of the (IL10)2-Fc format include XENP24628, XENP24629, XENP24630, and XENP24631, sequences for which are depicted in  FIG. 17 . 
     Another embodiment is the Fc-(IL10) 2  format (cartoon schematic depicted in  FIG. 16B ) which comprises two identical monomers, each monomer comprising an IL-10 monomer covalently attached to the C-terminus of a homodimeric Fc chain. Illustrative proteins of the Fc-(IL10) 2  format include XENP24632, XENP24633, and XENP246334, sequences for which are depicted in  FIG. 18 . 
     Yet another embodiment is the (IL10-NC-IL10)-heteroFc format (cartoon schematic depicted in  FIG. 16C ) which comprises a first monomer comprising a first IL-10 monomer covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a domain linker) and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”, while a second IL-10 monomer is transfected separately so that a non-covalent IL-10 dimer is formed. Illustrative proteins of the (IL10-NC-IL10)-heteroFc format include XENP25955, sequences for which are depicted in  FIG. 19 . 
     In some embodiments, the IL-10 monomers of this format comprise any of the L-10 monomer domains (e.g., the variant IL-10 monomer domain) described herein (e.g., those shown in  FIGS. 55, 57, 64, 67, 70A-70B, and 73 , the corresponding SEQ ID NOs, and the sequence listing). 
     B. scIL10-Fc Fusion Format 
     In another aspect, the present disclosure provides a format that pre-complexes the IL-10 homodimer as a single-chain IL-10 complex (or “scIL-10”) wherein a first IL-10 monomer is covalently attached to a second IL-10 monomer. One category of IL-10 fusions utilizing the scIL-10 are referred to herein as scIL10-Fc fusions (cartoon schematics depicted in  FIG. 20 ). 
     In some embodiments, the scIL-10 of this format comprises an amino acid sequence such as, but not limited, to SEQ ID NO:23 and any of the scIL10 variants described herein (e.g., those shown in  FIGS. 21A-21C, 22, 35A-35D, 39A-39G, 40A-40M, 41A-41F, 48, 49A-49B, 53, 55, 56A-56C, 58, 59A-59H ,  60 ,  64 ,  65 A- 65 B,  66 A- 66 D,  67 ,  68 ,  69 ,  70 A- 70 B,  73 ,  78 A- 78 G,  79 A- 79 G, and  86 A- 86 D, the corresponding SEQ ID NOS, and the sequence listing). In some embodiments, the scIL-10 component comprises an amino acid sequence having at least 90% (e.g., at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more) sequence identity to SEQ ID NO:23. 
     One embodiment is the scIL10-heteroFc format (cartoon schematic depicted in  FIG. 20A ), which comprises a first monomer comprising a scIL-10 covalently attached to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative protein of the scIL10-heteroFc format include XENP25238, XENP25239, XENP25240, XENP25241, XENP25880, and XENP28295, sequences for which are depicted in  FIGS. 21A-21C  and the corresponding SEQ ID NOS in the sequence listing. 
     In some embodiments, the scIL10-heteroFc fusion proteins comprise the sequences set forth in  FIGS. 78A-78G  and the sequence listing for XENP30003, XENP30004, XENP30005, XENP30006, XENP30007, XENP30008, XENP30009, XENP30010, XENP30011, XENP30012, XENP30013, XENP30014, and XENP30015. XENP30007 is also referred to as scIL10.104-Fc. XENP30008 is also referred to as scIL10.105-Fc. XENP30010 is also referred to as scIL10.107-Fc. 
     In some embodiments, the heteroFc-scIL10 fusion proteins comprise the sequences set forth in  FIGS. 79A-79G  and sequence listing for XENP30016, XENP30017, XENP30018, XENP30019, XENP30020, XENP30021, XENP30022, XENP30023, XENP30024, XENP30025, XENP30026, XENP30027, and XENP30028. 
     In some embodiments, the scIL10 fusion proteins containing M428L/N434S substitutions in the Fc domains comprise the sequences set forth in  FIGS. 86A-86D  and the sequence listing for XENP31091, XENP31092, XENP31093, XENP31094, XENP31095, XENP31096, XENP31830, and XENP31831. 
     Another embodiment is the heteroFc-scIL10 format (cartoon schematic depicted in  FIG. 20B ), which comprises a first monomer comprising a scIL-10 covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a domain linker) and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative protein of the heteroFc-scIL10 is XENP28740, sequences for which are depicted in  FIG. 22  and the corresponding SEQ ID NOS in the sequence listing. 
     In some embodiments, the Fc fusion proteins in this exemplary format comprise the format pictured in  FIG. 20A  with IL-10 variants and/or amino acid substitutions in the Fc domain. In some embodiments, the Fc fusion proteins in this exemplary format have the sequences set forth in  FIG. 21A  and the sequence listing for the corresponding sequence identifiers. In some embodiments, the Fc fusion proteins have the sequences set forth in  FIGS. 78A-78G  and sequence listing for XENP30003, XENP30004, XENP30005, XENP30006, XENP30007, XENP30008, XENP30009, XENP30010, XENP30011, XENP30012, XENP30013, XENP30014, and XENP30015. In further embodiments, the Fc fusion proteins in this exemplary format have the sequences set forth in  FIGS. 78A-78G  for XENP30005 (SEQ ID NO:25 and SEQ ID NO:26), XENP30008 (SEQ ID NO:27 and SEQ ID NO:28), and XENP30013 (SEQ ID NO:29 and SEQ ID NO:30). In still further embodiments, the Fc fusion proteins in this exemplary format comprise the sequences set forth  FIGS. 78A-78G  for XENP30005, XENP30008, and XENP30013 with the additional amino acid modifications selected from the group (singly or in any combination): G445del, K447del, G445del/K447del, M428L, N434S, and M428L/N434S, according to EU numbering. 
     C. IL10M1-Fc Fusion 
     In another aspect, the present disclosure provides a format engineered with the aim to circumvent the requirement for domain swapping between two IL-10 monomers. As discussed above, disruption of the non-covalent interaction which forms the biologically active IL-10 homodimer results in biologically inactive IL-10 monomers. However, Josephson et al. (2000) reported “IL-10M1” (or “IL10M1”; sequence depicted in  FIG. 15D ) which is a biologically active IL-10 monomer generated by engineering a Gly-Ser linker (GGGSGG; SEQ ID NO: 39) between helices D and E of an IL-10 monomer. Josephson et al. reported that IL-10M1 is capable of binding IL-10R1 and recruiting IL-10R2 to induce IL-10 cellular responses. Accordingly, in this aspect, the Fc fusion protein utilizes IL10M1, and such a format is referred to herein as IL10M1-Fc fusions (cartoon schematics depicted in  FIGS. 23A-23F ). 
     In some embodiments, the IL10M1 of this format comprises an amino acid sequence such as, but not limited, to SEQ ID NO:24 and any of the IL10M1 variants described herein (e.g., those shown in  FIGS. 36A-36E, 55, 57, 64, 67, 70A-70B, 71A-71E, 73, 74A-74B, 75A-75B, and 76A-76D , the corresponding SEQ ID NOs, and the sequence listing). In some embodiments, the IL10M1 variants comprises one or more substitutions selected from the group consisting of N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, E151Q, Q38E/D41N, Q38E/Q42E, Q38E/N45D, Q38E/E142Q, Q38E/D144N, D41N/Q42E, D41N/Q42E, D41N/N45D, D41N/E142Q, D41N/D144N, Q42E/N45D, Q42E/E142Q, Q42E/D144N, N45D/E142Q, N45D/D144N, E142Q/D144N, N21D/Q42E, N21D/N45D, N21D/E151Q, N21D/N45E, Q42E/E151Q, N45D/E151Q, N21D/Q42E/N45D, N21D/Q42E/E151Q, Q42E/N45D/E151Q, N21D/Q42E/N45E, and N21D/Q42E/N45D/E151Q. In some embodiments, the IL10M1 component comprises an amino acid sequence having at least 90% (e.g., at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more) sequence identity to SEQ ID NO:24. 
     In some instances, the IL10M1 component of the format comprises an amino acid sequence selected from the group consisting of the sequence depicted in  FIGS. 75A-75B  and the sequence listing for the corresponding sequence identifiers. In some embodiments, the IL10M1 component comprises a linker (e.g., an insert peptide) selected from the group consisting of PGGSGG (SEQ ID NO: 40), GPGSGG (SEQ ID NO: 41), GGPSGG (SEQ ID NO: 42), GGGPGG (SEQ ID NO: 43), GGGSPG (SEQ ID NO: 44), GGGSGP (SEQ ID NO: 45), GGGGG (SEQ ID NO: 46), GGGG (SEQ ID NO: 47), GGG, GG, G, and GGGGSGGGGS (SEQ ID NO: 32). 
     In one embodiment, the (IL10M1) 1 -heteroFc (cartoon schematic depicted in  FIG. 23E ) comprises an IL10M1 covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative protein of the (IL10M1)1-heteroFc format is XENP14246, sequences for which are depicted in  FIG. 24 . In another embodiment, the heteroFc-(IL10M1) 1  format (cartoon schematic depicted in  FIG. 23F ) comprises an IL10M1 covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative protein of the heteroFc-(IL10M1)1 format is XENP14247, sequences for which are depicted in  FIG. 25  and the corresponding SEQ ID NOS in the sequence listing. In some embodiments, the (IL10M1) 1 -heteroFc fusion proteins comprise the sequences set forth in  FIGS. 37A-37E  and the sequence listing for XENP25753, XENP25754, XENP25755, XENP25756, XENP25757, XENP25758, XENP25759, XENP25760, XENP25761, XENP25763, XENP25766, XENP25767, and XENP25768 and the corresponding sequence identifiers. 
     In yet another embodiment, the (IL10M1) 2 -Fc format (cartoon schematic depicted in  FIG. 23A ) comprises two identical monomers, wherein each monomer comprising an IL10M1 covalently attached to the N-terminus of a homodimeric Fc chain. An illustrative protein of the (IL10M1) 2 -Fc format is XENP25236, sequences for which are depicted in  FIG. 26 . In a further embodiment, the Fc-(IL10M1) 2  format (cartoon schematic depicted in  FIG. 23B ) comprises two identical monomers, wherein each monomer comprising an IL10M1 covalently attached to the C-terminus of a homodimeric Fc chain. An illustrative protein of the Fc-(IL10M1) 2  format is XENP25237, sequences for which are depicted in  FIG. 27  and the corresponding SEQ ID NOS in the sequence listing. 
     In a further embodiment, the (IL10M1) 2 -heteroFc format (cartoon schematic depicted in  FIG. 23C ) comprises a first monomer comprising a first IL10M1 covalently attached to a second IL10M1 (optionally via a linker) further covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative protein of the (IL10M1) 2 -heteroFc format is XENP26887, sequences for which are depicted in  FIG. 28  and the corresponding SEQ ID NOS in the sequence listing. 
     D. splitIL10-Fc Fusion 
     In another aspect, instead of utilizing a Gly-Ser linker between IL10(A-D) and IL10(E-F) domains as in IL10M1, a biologically active IL-10 monomer was generated by “splitting” the IL-10 monomer into its two domains (i.e. hIL-10(A-D) and hIL-10(E-F), sequences for which are depicted respectively in  FIGS. 15A-15B  and SEQ ID NO:21 and SEQ ID NO:22), and that dimerization of the IL-10 domains would provide for a biologically active molecule referred to herein as a “splitIL10”. Accordingly, the present disclosure provides formats referred to herein as splitIL10-Fc fusions (cartoon schematics depicted in  FIGS. 29A-29D ). 
     In some embodiments, the hIL-10(A-D) and hIL-10(E-F) domains of this format comprise amino acid sequences such as, but not limited, to SEQ ID NO:21 and SEQ ID NO:22, respectively and any of the hIL-10(A-D) and hIL-10(E-F) domain variants described herein (e.g., those shown in  FIGS. 55, 57, 64, 67, 70A-70B, and 73 , the corresponding SEQ ID NOS, and the sequence listing). 
     One embodiment is the splitIL10-heteroFc format (cartoon schematic depicted in  FIG. 29A ), which comprises a first monomer comprising hIL-10(A-D) covalently attached to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising hIL-10(E-F) covalently attached to the N-terminus of a complementary second heterodimeric Fc chain, so that dimerization of the heterodimeric Fc chains forces dimerization of the IL-10 domains. Illustrative proteins of the splitIL10-heteroFc format include XENP25242, XENP25243, and XENP25244, sequences for which are depicted in  FIG. 30  and the corresponding SEQ ID NOS in the sequence listing. 
     In another embodiment, the heteroFc-splitIL10 format (cartoon schematics depicted in  FIG. 29B ) comprises a first monomer comprising a hIL-10(A-D) domain covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a linker) and a second monomer comprising a hIL-10(E-F) domain covalently attached the C-terminus of a complementary second heterodimeric Fc chain (optionally via a linker). Illustrative proteins of the heteroFc-splitIL10 format include XENP25879, sequences for which are depicted in  FIG. 31  and the corresponding SEQ ID NOS in the sequence listing. 
     VII. Useful Targeted Formats of the Invention 
     As shown in  FIGS. 87, 88, 89, and 90 , there are a number of useful formats of the targeted IL-10 fusion proteins of the invention. In general, the fusion proteins of the invention have several components: an IL-10 component, an Fc component, and an antigen binding domain, all of which can take different forms as outlined herein and each of which can be combined with the other component in any configuration. As will be appreciated, the IL-10 component in any of the formats described herein may comprise an IL-10 with a histidine at position 109 or a leucine at position 109. The IL-10 component may further include any of the IL-10 monomer, IL10M1, scIL10, and splitIL10 variants described herein and known in the art. As described above, the Fc domains of such targeted IL-10 fusion proteins include modifications that promote heterodimerization of the Fc domains. 
     A. Targeted IL10-Fc Fusion Formats 
       FIG. 87A - FIG. 87D  depict illustrative formats for targeted IL-10 fusions based on the IL10-Fc category, herein referred to as the “targeted IL10-Fc” category.  FIG. 88A - FIG. 88E  depict illustrative formats for targeted IL-10 fusions based on the scIL10-Fc category, herein referred to as the “targeted scIL10-Fc” category.  FIG. 89A - FIG. 89M  depict illustrative formats for targeted IL-10 fusions based on the IL10M1-Fc category, herein referred to as the “targeted IL10M1-Fc” category.  FIG. 90A - FIG. 90H  depict illustrative formats for targeted IL-10 fusions based on the splitIL10-Fc category, herein referred to as the “targeted splitIL10-Fc” category. 
     In some embodiments, targeted IL-10 Fc fusion proteins of the present invention comprise an antigen binding domain such as a Fab or an scFv. In some embodiments, the “mAb-IL10” format (see, e.g.,  FIG. 87A ) comprises two identical monomers, each monomer comprising an antigen-binding domain covalently linked to the N-terminus of a homodimeric Fc chain which is covalently linked via the C-terminus, optionally via a linker, to an IL-10 monomer. In some embodiments, the “IL10-mAb” format (see, e.g.,  FIG. 87B ) comprises two identical monomers, each monomer comprising an IL-10 monomer covalently linked, optionally via a linker, to an antigen-binding domain which is covalently linked to the N-terminus of a homodimeric Fc chain. In some embodiments, the “mAb-central-IL10” format (see, e.g.,  FIG. 87C ) comprises two identical monomers, each monomer comprising an antigen-binding domain covalently linked to an IL-10 monomer which is covalently linked, optionally via a linker, to a homodimeric Fc chain. It should be noted that while the antigen-binding domains are depicted as Fabs, the antigen-binding domain can be any antigen binding molecule as defined herein, such as an scFv. In some embodiments, the “anti-X×IL10-heteroFc” format (see, e.g.,  FIG. 87D ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first IL-10 monomer covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker), and a second IL-10 monomer transfected separately so that it forms a non-covalent interaction with the first IL-10 monomer. As will be appreciated, the antigen binding domain for any of the formats described herein, including those illustrated in  FIGS. 87A-87D , may be directed to any suitable antigen, including without limitation CD8, NKG2D, PD-1, and TIGIT. In some embodiments, any IL-10 monomer or variant thereof described herein can be used in a targeted IL10-Fc format. 
     In some embodiments, the CD8 antigen binding domain of the formats described herein comprises the variable heavy chain and variable light chain pairs depicted in  FIG. 92  and the sequences of the corresponding SEQ ID NOS in the sequence listing. Non-limiting examples of useful variable heavy chain and variable light chain pairs of a CD8 ABD include OKT8_H2_L1 and 1C11B3_H1_L1. 
     In some embodiments, the NKG2D antigen binding domain of the formats described herein comprises the variable heavy chain and variable light chain pairs depicted in  FIG. 93A-93C  and the sequences of the corresponding SEQ ID NOS in the sequence listing. Non-limiting examples of useful variable heavy chain and variable light chain pairs of an NKG2D ABD include MS[NKG2D] H0_L0, 1D7B4[NKG2D]_H1_L1, KYK-1.0[NKG2D]_H1_L1, KYK-2.0[NKG2D]_H0_L0, 11B2D10[NKG2D]_H0_L0, 6E5A7[NKG2D]_H0_L0, 6H7E7[NKG2D]_H0_L0, mAb E[NKG2D]_H1_L1, 16F31[NKG2D]_H1_L1, mAb D[NKG2D]_H1_L1, 1 D7B4[NKG2D]_H1_L1, mAb A[NKG2D]_H1_L1, mAb A[NKG2D]_H2_L1, mAb A[NKG2D]_H1_L2, mAb A[NKG2D]_H2_L2, mAb B[NKG2D]_H1_L1, mAb B[NKG2D]_H1_L1.1, mAb B[NKG2D]_H1_L2, mAb B[NKG2D]_H2_L1, mAb B[NKG2D]_H2_L1.1, mAb B[NKG2D]_H2_L2, mAb B[NKG2D]_H3_L1, mAb B[NKG2D]_H3_L1.1, mAb B[NKG2D]_H3_L2, mAb C[NKG2D]_H1_L1, mAb C[NKG2D]_H2_L1, mAb C[NKG2D]_H1_L2, and mAb C[NKG2D]_H2_L2. 
     In some embodiments, the PD-1 antigen binding domain of the formats described herein comprises the variable heavy chain and variable light chain pairs depicted in  FIG. 100A-100G  and the sequences of the corresponding SEQ ID NOS in the sequence listing. Non-limiting examples of useful variable heavy chain and variable light chain pairs of a PD-1 ABD include 1C11[PD-1]_H0L0, 1C11[PD-1]_H3L3, 1C11[PD-1]_H3.240_L3.148, 1C11[PD-1]_H3.241_L3.148, 1C11[PD-1]_H3.234_L3.144, 1C11[PD-1]_H3.241_L3.92, 1C11[PD-1]_H3.303_L3.152, 1C11_H3.329_L3.220, 1C11_H3.328_L3.152, pembrolizumab variable heavy chain and variable light chain, nivolumab variable heavy chain and variable light chain, pidilizumab variable heavy chain and variable light chain, MK-3475 variable heavy chain and variable light chain, BAP049 Clone E variable heavy chain and variable light chain, BAP049 Clone B variable heavy chain and variable light chain, H7798N[PD-1] variable heavy chain and variable light chain, h1H3 Var 6[PD-1] variable heavy chain and variable light chain, APE2058[PD-1] variable heavy chain and variable light chain, H005-1[PD-1] variable heavy chain and variable light chain, 317-4B6[PD-1] variable heavy chain and variable light chain, 326-4A3[PD-1] variable heavy chain and variable light chain, hPD-1 mAb 7 (1.2)[PD-1] variable heavy chain and variable light chain, Clone 38[PD-1] variable heavy chain and variable light chain, Clone 39[PD-1] variable heavy chain and variable light chain, Clone 41[PD-1] variable heavy chain and variable light chain, Clone 48[PD-1] variable heavy chain and variable light chain, PD1-17[PD-1] variable heavy chain and variable light chain, PD1-28[PD-1] variable heavy chain and variable light chain, PD1-33[PD-1] variable heavy chain and variable light chain, PD1-35[PD-1] variable heavy chain and variable light chain, LOPD180 variable heavy chain and variable light chain, Ab948 variable heavy chain and variable light chain, humanized EH-12.2H7[PD-1] variable heavy chain and variable light chain, RG1H10 variable heavy chain and variable light chain, RG1H10-H2A-22-1S variable heavy chain and variable light chain, RG1H10-H2A-27-2S variable heavy chain and variable light chain, RG1H10-3C variable heavy chain and variable light chain, RG1H10-16C variable heavy chain and variable light chain, RG1H10-17C variable heavy chain and variable light chain, RG1H10-19C variable heavy chain and variable light chain, RG1H10-21C variable heavy chain and variable light chain, RG1H10-23C2 variable heavy chain and variable light chain, mAb7[PD-1], and PD1AB-6[PD-1] variable heavy chain and variable light chain. 
     In some embodiments, the non-competing PD-1 antigen binding domain of the formats described herein comprises the variable heavy chain and variable light chain pairs depicted in  FIG. 104A-104B  and the sequences of the corresponding SEQ ID NOS in the sequence listing. Non-limiting examples of useful variable heavy chain and variable light chain pairs of a non-competing PD-1 ABD include mAb A[PD-1]_H1_L1, mAb B[PD-1]_H1_L1, mAb C[PD-1]_H1_L1, mAb C[PD-1]_H1_L1.1, mAb C[PD-1]_H1_L1.3, mAb C[PD-1]_H1_L1.45, mAb C[PD-1]_H1_L1.117, mAb C[PD-1]_H1_L1.129, mAb C[PD-1]_H1_L1.135, mAb C[PD-1]_H1_L1.136, mAb C[PD-1]_H1_L1.140, mAb C[PD-1]_H1_L2, mAb C[PD-1]_H1.19_L1, mAb C[PD-1]_H1.19_L1.1, mAb C[PD-1]_H1.19_L1.3, mAb C[PD-1]_H1.19_L1.45, mAb C[PD-1]_H1.19_L1.117, mAb C[PD-1]_H1.19_L1.129, mAb C[PD-1]_H1.19_L1.135, mAb C[PD-1]_H1.19_L1.136, mAb C[PD-1]_H1.19_L1.140, mAb C[PD-1]_H1.19_L2, mAb C[PD-1]_H1.48_L1, mAb C[PD-1]_H1.48_L1.1, mAb C[PD-1]_H1.48_L1.3, mAb C[PD-1]_H1.48_L1.45, mAb C[PD-1]_H1.48_L1.117, mAb C[PD-1]_H1.48_L1.129, mAb C[PD-1]_H1.48_L1.135, mAb C[PD-1]_H1.48_L1.136, mAb C[PD-1]_H1.48_L1.140, mAb C[PD-1]_H1.48_L2, mAb C[PD-1]_H1.125_L1, mAb C[PD-1]_H1.125_L1.1, mAb C[PD-1]_H1.125_L1.3, mAb C[PD-1]_H1.125_L1.45, mAb C[PD-1]_H1.125_L1.117, mAb C[PD-1]_H1.125_L1.129, mAb C[PD-1]_H1.125_L1.135, mAb C[PD-1]_H1.125_L1.136, mAb C[PD-1]_H1.125_L1.140, mAb C[PD-1]_H1.125_L2, mAb C[PD-1]_H1.130_L1, mAb C[PD-1]_H1.130_L1.1, mAb C[PD-1]_H1.130_L1.3, mAb C[PD-1]_H1.130_L1.45, mAb C[PD-1]_H1.130_L1.117, mAb C[PD-1]_H1.130_L1.129, mAb C[PD-1]_H1.130_L1.135, mAb C[PD-1]_H1.130_L1.136, mAb C[PD-1]_H1.130_L1.140, mAb C[PD-1]_H1.130_L2, mAb C[PD-1]_H1.132_L1, mAb C[PD-1]_H1.132_L1.1, mAb C[PD-1]_H1.132_L1.3, mAb C[PD-1]_H1.132_L1.45, mAb C[PD-1]_H1.132_L1.117, mAb C[PD-1]_H1.132_L1.129, mAb C[PD-1]_H1.132_L1.135, mAb C[PD-1]_H1.132_L1.136, mAb C[PD-1]_H1.132_L1.140, mAb C[PD-1]_H1.132_L2, mAb C[PD-1]_H1.169_L1, mAb C[PD-1]_H1.169_L1.1, mAb C[PD-1]_H1.169_L1.3, mAb C[PD-1]_H1.169_L1.45, mAb C[PD-1]_H1.169_L1.117, mAb C[PD-1]_H1.169_L1.129, mAb C[PD-1]_H1.169_L1.135, mAb C[PD-1]_H1.169_L1.136, mAb C[PD-1]_H1.169_L1.140, mAb C[PD-1]_H1.169_L2, mAb C[PD-1]_H1.175_L1, mAb C[PD-1]_H1.175_L1.1, mAb C[PD-1]_H1.175_L1.3, mAb C[PD-1]_H1.175_L1.45, mAb C[PD-1]_H1.175_L1.117, mAb C[PD-1]_H1.175_L1.129, mAb C[PD-1]_H1.175_L1.135, mAb C[PD-1]_H1.175_L1.136, mAb C[PD-1]_H1.175_L1.140, mAb C[PD-1]_H1.175_L2, mAb C[PD-1]_H2_L1, mAb C[PD-1]_H2_L1.1, mAb C[PD-1]_H2_L1.3, mAb C[PD-1]_H2_L1.45, mAb C[PD-1]_H2_L1.117, mAb C[PD-1]_H2_L1.129, mAb C[PD-1]_H2_L1.135, mAb C[PD-1]_H2_L1.136, mAb C[PD-1]_H2_L1.140, and mAb C[PD-1]_H2_L2. 
     In some embodiments, the TIGIT antigen binding domain of the formats described herein comprises the variable heavy chain and variable light chain pairs depicted in  FIG. 122A-122C  and the sequences of the corresponding SEQ ID NOS in the sequence listing. Non-limiting examples of useful variable heavy chain and variable light chain pairs of a TIGIT ABD include 2A5B4[TIGIT]_H1_L1, Genentech_4.1 D3.Q1E(tiragolumab)_H0_L0, 10A7 [TIGIT] variable heavy chain and variable light chain, 1F4[TIGIT] variable heavy chain and variable light chain, 4.1D3[TIGIT] variable heavy chain and variable light chain, Hu14D7 VH1_VL1, Hu14D7 VH1_VL2, Hu14D7 VH1_VL3, Hu14D7 VH2_VL1, Hu14D7 VH2_VL2, Hu14D7 VH2_VL3, Hu14D7 VH3_VL1, Hu14D7 VH3_VL2, Hu14D7 VH3_VL3, Hu26B10 VH1_VL1, Hu26B10 VH1_VL2, Hu26B10 VH1_L3, Hu26B10 VH2_VL1, Hu26B10 VH2_VL2, Hu26B10 VH2_VL3, Hu26B10 VH3_VL1, Hu26B10 VH3_L2, Hu26B10 VH3_VL3, MEB125.31C6.A1.205 VH4/VL1, MEB125.31C6.A1.205 VH5/VL4, MEB125.31C6.A1.205 VH5/VL3, 15A6 variable heavy chain and variable light chain, 22G2 variable heavy chain and variable light chain, 11G11 variable heavy chain and variable light chain, 10D7 variable heavy chain and variable light chain, 313R19 variable heavy chain and variable light chain, and etigilimab variable heavy chain and variable light chain. 
     B. Targeted scIL10-Fc Fusion Formats 
     In further embodiments, formats such as those pictured in  FIG. 88A - FIG. 88E  are provided by the present disclosure.  FIG. 88  depicts illustrative formats for targeted IL-10 fusions based on the scIL10-Fc category, herein referred to as the “targeted scIL10-Fc” category. In some embodiments, the “anti-X×scIL10-heteroFc” format (see, e.g.,  FIG. 88A ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker). In some embodiments, the “anti-X× heteroFc-scIL10” format (see, e.g.,  FIG. 88B ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a second heterodimeric Fc chain covalently linked via the C-terminus to a scIL-10 (optionally via a domain linker). In some embodiments, the “anti-X× heteroFc-scIL10” format comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain which is covalently linked via the C-terminus to a scIL-10 (optionally via a domain linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. In some embodiments, the “(anti-X) 2 -heteroFc-scIL10” format (see, e.g.,  FIG. 88C ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to the N-terminus of a second heterodimeric Fc chain which is covalently linked via the C-terminus to a scIL-10 (optionally via a domain linker). In some embodiments, the “(anti-X) 2 -central-scIL10” format (see, e.g.,  FIG. 88D ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to a scIL-10 which is covalently linked to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). In some embodiments, the “scIL10-(anti-X) 2 -heteroFc” format (see, e.g.,  FIG. 88E ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently linked, optionally via a linker, to an antigen-binding domain which is covalently linked to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). It should be noted that while the antigen-binding domains are depicted as Fabs, the antigen-binding domain can be any antigen binding molecule as defined herein, such as an scFv. As will be appreciated, the antigen binding domain for any of the formats described herein, including those illustrated in  FIG. 88A - FIG. 88E , may be directed to any suitable antigen, including without limitation CD8, NKG2D, PD-1, and TIGIT. 
     In some embodiments, the targeted IL-10 Fc fusion protein (e.g., targeted anti-CD8 ABD×scIL10 heterodimeric Fc fusion protein) comprises a first monomer comprising an anti-CD8 antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the N-terminus of a second heterodimeric Fc chain. In some embodiments, the scIL-10 is covaletly attached to the second Fc chain via a domain linker. In some embodiments, the anti-CD8 ABD comprises the VH and VL combination of 1C11B3_H1_L1. In some embodiments, the scIL-10 of the fusion protein comprises the sequence of  FIG. 15C  or any of the scIL10 monomer variants described herein. In some embodiments, each monomer of the scIL10 comprises an amino acid sequence as set forth in  FIGS. 39A-39G, 55, 56A-56C, 57, 58, 64, and 65A-65B . In some embodiments, the scIL is selected from the group consisting of huIL10_huIL10, huIL10.22_huIL10.22, huIL10.38_huIL10.38, huIL10.64_huIL10.64, huIL10.102_huIL10.102, huIL10.104_huIL10.104, huIL10.105_huIL10.105, and huIL10.107_huIL10.107 as depicted in the figures. In some embodiments, the scIL monomer is selected from the group consisting of huIL10, huIL10.22, huIL10.38, huIL10.64, huIL10.102, huIL10.104, huIL10.105, and huIL10.107 as depicted in the figures. 
     In some embodiments, the targeted anti-CD8 ABD×scIL10 heterodimeric Fc fusion protein comprises a first monomer comprising a scIL10, a domain linker, and a first Fc domain; a second monomer comprising an anti-CD8 VH domain and a second Fc domain; and an anti-CD8 VL domain such that the VH domain and VL domain form an anti-CD8 ABD. In some instances, the scIL10 comprises two IL-10 monomers. In some instances, the scIL10 comprises two IL-10 monomers covalently attached by a linker. In some embodiments, the targeted IL-10 Fc fusion protein is XENP25415, XENP25791, XENP25794, XENP26883, and XENP26879 as depicted in  FIG. 96A - FIG. 96C  and  FIG. 98  and in the sequences corresponding to the SEQ ID NOS in the sequence listing. 
     In some embodiments, the targeted IL-10 Fc fusion protein (e.g., targeted anti-NKG2D ABD×scIL10 heterodimeric Fc fusion protein) comprises a first monomer comprising an anti-NKG2D antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the N-terminus of a second heterodimeric Fc chain. In some embodiments, the scIL-10 is covaletly attached to the second Fc chain via a domain linker. In some embodiments, the anti-NKG2D ABD comprises the VH and VL combination of any selected from the group consisting of MS[NKG2D] H0_L0, 1D7B4[NKG2D]_H1_L1, KYK-1.0 [NKG2D]_H1_L1, KYK-2.0[NKG2D]_H0_L0, 11B2D10[NKG2D]_H0_L0, 6E5A7[NKG2D]_H0_L0, 6H7E7[NKG2D]_H0_L0, mAb E[NKG2D]_H1_L1, 16F31[NKG2D]_H1_L1, mAb D[NKG2D]_H1_L1, 1 D7B4[NKG2D]_H1_L1, mAb A[NKG2D]_H1_L1, mAb A[NKG2D]_H2_L1, mAb A[NKG2D]_H1_L2, mAb A[NKG2D]_H2_L2, mAb B[NKG2D]_H1_L1, mAb B[NKG2D]_H1_L1.1, mAb B[NKG2D]_H1_L2, mAb B[NKG2D]_H2_L1, mAb B[NKG2D]_H2_L1.1, mAb B[NKG2D]_H2_L2, mAb B[NKG2D]_H3_L1, mAb B[NKG2D]_H3_L1.1, mAb B[NKG2D]_H3_L2, mAb C[NKG2D]_H1_L1, mAb C[NKG2D]_H2_L1, mAb C[NKG2D]_H1_L2, and mAb C[NKG2D]_H2_L2. In some embodiments, the scIL-10 of the fusion protein comprises the sequence of  FIG. 15C  or any of the scIL10 monomer variants described herein. In some embodiments, each monomer of the scIL10 comprises an amino acid sequence as set forth in  FIGS. 39A-39G, 55, 56A-56C, 57, 58, 64, and 65A-65B . In some embodiments, the scIL is selected from the group consisting of huIL10_huIL10, huIL10.22_huIL10.22, huIL10.38_huIL10.38, huIL10.64_huIL10.64, huIL10.102_huIL10.102, huIL10.104_huIL10.104, huIL10.105_huIL10.105, and huIL10.107_huIL10.107 as depicted in the figures. In some embodiments, the scIL monomer is selected from the group consisting of huIL10, huIL10.22, huIL10.38, huIL10.64, huIL10.102, huIL10.104, huIL10.105, and huIL10.107 as depicted in the figures. 
     In some embodiments, the targeted anti-NKG2D ABD×scIL10 heterodimeric Fc fusion protein comprises a first monomer comprising a scIL10, a domain linker, and a first Fc domain; a second monomer comprising an anti-NKG2D VH domain and a second Fc domain; and an anti-NKG2D VL domain such that the VH domain and VL domain form an anti-NKG2D ABD. In some instances, the scIL10 comprises two IL-10 monomers. In some instances, the scIL10 comprises two IL-10 monomers covalently attached by a linker. In some embodiments, the NKG2D targeted IL-10 Fc fusion protein is XENP25952, XENP30526, XENP30527, XENP30528, and XENP31819 as depicted in  FIG. 97A - FIG. 97C  and in the sequences corresponding to the SEQ ID NOS in the sequence listing. 
     In some embodiments, the targeted IL-10 Fc fusion protein (e.g., targeted anti-PD-1 ABD×scIL10 heterodimeric Fc fusion protein) comprises a first monomer comprising an anti-PD-1 antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the N-terminus of a second heterodimeric Fc chain. In certain embodiments, the targeted IL-10 Fc fusion protein of the “anti-PD-1× heteroFc-scIL10” format comprises a first monomer comprising an anti-PD-1 antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the C-terminus of a second heterodimeric Fc chain. In some embodiments, the scIL-10 is covaletly attached to the second Fc chain via a domain linker. In some embodiments, the anti-PD-1 ABD comprises the VH and VL combination of any selected from the group consisting of 1C11[PD-1]_H0L0, 1C11[P, D-1]_H3L3, 1C11[PD-1]_H3.240_L3.148, 1C11[PD-1]_H3.241_L3.148, 1C11[PD-1]_H3.234_L3.144, 1C11[PD-1]_H3.241_L3.92, 1C11[PD-1]_H3.303_L3.152, 1C11_H3.329_L3.220, 1C11_H3.328_L3.152, pembrolizumab variable heavy chain and variable light chain, nivolumab variable heavy chain and variable light chain, pidilizumab variable heavy chain and variable light chain, MK-3475 variable heavy chain and variable light chain, BAP049 Clone E variable heavy chain and variable light chain, BAP049 Clone B variable heavy chain and variable light chain, H7798N[PD-1] variable heavy chain and variable light chain, h1H3 Var 6[PD-1] variable heavy chain and variable light chain, APE2058[PD-1] variable heavy chain and variable light chain, H005-1[PD-1] variable heavy chain and variable light chain, 317-4B6[PD-1] variable heavy chain and variable light chain, 326-4A3[PD-1] variable heavy chain and variable light chain, hPD-1 mAb 7 (1.2)[PD-1] variable heavy chain and variable light chain, Clone 38[PD-1] variable heavy chain and variable light chain, Clone 39[PD-1] variable heavy chain and variable light chain, Clone 41[PD-1] variable heavy chain and variable light chain, Clone 48[PD-1] variable heavy chain and variable light chain, PD1-17[PD-1] variable heavy chain and variable light chain, PD1-28[PD-1] variable heavy chain and variable light chain, PD1-33[PD-1] variable heavy chain and variable light chain, PD1-35[PD-1] variable heavy chain and variable light chain, LOPD180 variable heavy chain and variable light chain, Ab948 variable heavy chain and variable light chain, humanized EH-12.2H7[PD-1] variable heavy chain and variable light chain, RG1H10 variable heavy chain and variable light chain, RG1H10-H2A-22-1S variable heavy chain and variable light chain, RG1H10-H2A-27-2S variable heavy chain and variable light chain, RG1H10-3C variable heavy chain and variable light chain, RG1H10-16C variable heavy chain and variable light chain, RG1H10-17C variable heavy chain and variable light chain, RG1H10-19C variable heavy chain and variable light chain, RG1H10-21C variable heavy chain and variable light chain, RG1H10-23C2 variable heavy chain and variable light chain, mAb7[PD-1], and PD1AB-6[PD-1] variable heavy chain and variable light chain. In some embodiments, the scIL-10 of the fusion protein comprises the sequence of  FIG. 15C  or any of the scIL10 monomer variants described herein. In some embodiments, each monomer of the scIL10 comprises an amino acid sequence as set forth in  FIGS. 39A-39G, 55, 56A-56C, 57, 58, 64, and 65A-65B . In some embodiments, the scIL is selected from the group consisting of huIL10_huIL10, huIL10.22_huIL10.22, huIL10.38_huIL10.38, huIL10.64_huIL10.64, huIL10.102_huIL10.102, huIL10.104_huIL10.104, huIL10.105_huIL10.105, and huIL10.107_huIL10.107 as depicted in the figures. In some embodiments, the scIL monomer is selected from the group consisting of huIL10, huIL10.22, huIL10.38, huIL10.64, huIL10.102, huIL10.104, huIL10.105, and huIL10.107 as depicted in the figures. 
     In some embodiments, the targeted anti-PD-1 ABD×scIL10 heterodimeric Fc fusion protein comprises a first monomer comprising from N- to C-terminal: a scIL10, a domain linker, and a first Fc domain; a second monomer comprising from N- to C-terminal: an anti-PD-1 VH domain and a second Fc domain; and an anti-PD-1 VL domain such that the VH domain and VL domain form an anti-PD-1 ABD. In certain embodiments, the targeted anti-PD-1 ABD×scIL10 heterodimeric Fc fusion protein comprises a first monomer comprising from N- to C-terminal: a first Fc domain, a domain linker, and a scIL10; a second monomer comprising from N- to C-terminal: an anti-PD-1 VH domain and a second Fc domain; and an anti-PD-1 VL domain such that the VH domain and VL domain form an anti-PD-1 ABD. In some instances, the scIL10 comprises two IL-10 monomers. In some instances, the scIL10 comprises two IL-10 monomers covalently attached by a linker. In some embodiments, the PD-1 targeted IL-10 Fc fusion protein is XENP25953, XENP27830, XENP27831, XENP31269, XENP31270, XENP31271, and XENP31272 as depicted in  FIG. 101 ,  FIGS. 102A-102C , and  FIG. 103  and in the sequences corresponding to the SEQ ID NOS in the sequence listing. 
     In some embodiments, the targeted IL-10 Fc fusion protein (e.g., targeted non-competing anti-PD-1 ABD×scIL10 heterodimeric Fc fusion protein) comprises a first monomer comprising a non-competing anti-PD-1 antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the N-terminus of a second heterodimeric Fc chain. In certain embodiments, the targeted IL-10 Fc fusion protein of the “anti-PD-1× heteroFc-scIL10” format comprises a first monomer comprising a non-competing anti-PD-1 antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the C-terminus of a second heterodimeric Fc chain. In some embodiments, the scIL-10 is covaletly attached to the second Fc chain via a domain linker. In some embodiments, the anti-PD-1 ABD comprises the VH and VL combination of any selected from the group consisting of mAb A[PD-1]_H1_L1, mAb B[PD-1]_H1_L1, mAb C[PD-1]_H1_L1, mAb C[PD-1]_H1_L1.1, mAb C[PD-1]_H1_L1.3, mAb C[PD-1]_H1_L1.45, mAb C[PD-1]_H1_L1.117, mAb C[PD-1]_H1_L1.129, mAb C[PD-1]_H1_L1.135, mAb C[PD-1]_H1_L1.136, mAb C[PD-1]_H1_L1.140, mAb C[PD-1]_H1_L2, mAb C[PD-1]_H1.19_11, mAb C[PD-1]_H1.19_L1.1, mAb C[PD-1]_H1.19_L1.3, mAb C[PD-1]_H1.19_L1.45, mAb C[PD-1]_H1.19_L1.117, mAb C[PD-1]_H1.19_L1.129, mAb C[PD-1]_H1.19_L1.135, mAb C[PD-1]_H1.19_L1.136, mAb C[PD-1]_H1.19_L1.140, mAb C[PD-1]_H1.19_L2, mAb C[PD-1]_H1.48_11, mAb C[PD-1]_H1.48_L1.1, mAb C[PD-1]_H1.48_L1.3, mAb C[PD-1]_H1.48_L1.45, mAb C[PD-1]_H1.48_L1.117, mAb C[PD-1]_H1.48_L1.129, mAb C[PD-1]_H1.48_L1.135, mAb C[PD-1]_H1.48_L1.136, mAb C[PD-1]_H1.48_L1.140, mAb C[PD-1]_H1.48_L2, mAb C[PD-1]_H1.125_11, mAb C[PD-1]_H1.125_L1.1, mAb C[PD-1]_H1.125_L1.3, mAb C[PD-1]_H1.125_L1.45, mAb C[PD-1]_H1.125_L1.117, mAb C[PD-1]_H1.125_L1.129, mAb C[PD-1]_H1.125_L1.135, mAb C[PD-1]_H1.125_L1.136, mAb C[PD-1]_H1.125_L1.140, mAb C[PD-1]_H1.125_L2, mAb C[PD-1]_H1.130_11, mAb C[PD-1]_H1.130_L1.1, mAb C[PD-1]_H1.130_L1.3, mAb C[PD-1]_H1.130_L1.45, mAb C[PD-1]_H1.130_L1.117, mAb C[PD-1]_H1.130_L1.129, mAb C[PD-1]_H1.130_L1.135, mAb C[PD-1]_H1.130_L1.136, mAb C[PD-1]_H1.130_L1.140, mAb C[PD-1]_H1.130_L2, mAb C[PD-1]_H1.132_11, mAb C[PD-1]_H1.132_L1.1, mAb C[PD-1]_H1.132_L1.3, mAb C[PD-1]_H1.132_L1.45, mAb C[PD-1]_H1.132_L1.117, mAb C[PD-1]_H1.132_L1.129, mAb C[PD-1]_H1.132_L1.135, mAb C[PD-1]_H1.132_L1.136, mAb C[PD-1]_H1.132_L1.140, mAb C[PD-1]_H1.132_L2, mAb C[PD-1]_H1.169_11, mAb C[PD-1]_H1.169_L1.1, mAb C[PD-1]_H1.169_L1.3, mAb C[PD-1]_H1.169_L1.45, mAb C[PD-1]_H1.169_L1.117, mAb C[PD-1]_H1.169_L1.129, mAb C[PD-1]_H1.169_L1.135, mAb C[PD-1]_H1.169_L1.136, mAb C[PD-1]_H1.169_L1.140, mAb C[PD-1]_H1.169_L2, mAb C[PD-1]_H1.175_11, mAb C[PD-1]_H1.175_L1.1, mAb C[PD-1]_H1.175_L1.3, mAb C[PD-1]_H1.175_L1.45, mAb C[PD-1]_H1.175_L1.117, mAb C[PD-1]_H1.175_L1.129, mAb C[PD-1]_H1.175_L1.135, mAb C[PD-1]_H1.175_L1.136, mAb C[PD-1]_H1.175_L1.140, mAb C[PD-1]_H1.175_L2, mAb C[PD-1]_H2_L1, mAb C[PD-1]_H2_L1.1, mAb C[PD-1]_H2_L1.3, mAb C[PD-1]_H2_L1.45, mAb C[PD-1]_H2_L1.117, mAb C[PD-1]_H2_L1.129, mAb C[PD-1]_H2_L1.135, mAb C[PD-1]_H2_L1.136, mAb C[PD-1]_H2_L1.140, and mAb C[PD-1]_H2_L2. 
     In some embodiments, the targeted non-competing anti-PD-1 ABD×scIL10 heterodimeric Fc fusion protein comprises a first monomer comprising from N- to C-terminal: a scIL10, a domain linker, and a first Fc domain; a second monomer comprising from N- to C-terminal: an anti-PD-1 VH domain and a second Fc domain; and an anti-PD-1 VL domain such that the VH domain and VL domain form a non-competing anti-PD-1 ABD. In certain embodiments, the targeted non-competing anti-PD-1 ABD×scIL10 heterodimeric Fc fusion protein comprises a first monomer comprising from N- to C-terminal: a first Fc domain, a domain linker, and a scIL10; a second monomer comprising from N- to C-terminal: an anti-PD-1 VH domain and a second Fc domain; and an anti-PD-1 VL domain such that the VH domain and VL domain form a non-competing anti-PD-1 ABD. In some instances, the scIL10 comprises two IL-10 monomers. In some instances, the scIL10 comprises two IL-10 monomers covalently attached by a linker. In some embodiments, the non-competing PD-1 targeted IL-10 Fc fusion protein is XENP30520, XENP30521, XENP30522, XENP31266, XENP31267, and XENP31268 as depicted in  FIGS. 106A-106C  and in the sequences corresponding to the SEQ ID NOs in the sequence listing. XENP30520 is also referred to as αPD-1(mAb C_H1_L1.1)×huIL10.104. XENP30521 is also referred to as αPD-1(mAb C_H1_L1.1)×huIL10.105. XENP30522 is also referred to as αPD-1(mAb C_H1_L1.1)×huIL10.107. 
     In some embodiments, the targeted IL-10 Fc fusion protein (e.g., targeted non-competing anti-TIGIT ABD×scIL10 heterodimeric Fc fusion protein) comprises a first monomer comprising a non-competing anti-TIGIT antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the N-terminus of a second heterodimeric Fc chain. In certain embodiments, the targeted IL-10 Fc fusion protein of the “anti-TIGIT×heteroFc-scIL10” format comprises a first monomer comprising an anti-TIGIT antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the C-terminus of a second heterodimeric Fc chain. In some embodiments, the scIL-10 is covaletly attached to the second Fc chain via a domain linker. In some embodiments, the anti-TIGIT ABD comprises the VH and VL combination of any selected from the group consisting of 2A5B4[TIGIT]_H1_L1, Genentech_4.1 D3.Q1E(tiragolumab)_H0_L0, 10A7 [TIGIT] variable heavy chain and variable light chain, 1F4[TIGIT] variable heavy chain and variable light chain, 4.1D3[TIGIT] variable heavy chain and variable light chain, Hu14D7 VH1_VL1, Hu14D7 VH1_VL2, Hu14D7 VH1_VL3, Hu14D7 VH2_VL1, Hu14D7 VH2_VL2, Hu14D7 VH2_VL3, Hu14D7 VH3_VL1, Hu14D7 VH3_VL2, Hu14D7 VH3_VL3, Hu26B10 VH1_VL1, Hu26B10 VH1_VL2, Hu26B10 VH1_L3, Hu26B10 VH2_VL1, Hu26B10 VH2_VL2, Hu26B10 VH2_VL3, Hu26B10 VH3_VL1, Hu26B10 VH3_L2, Hu26B10 VH3_VL3, MEB125.31C6.A1.205 VH4/VL1, MEB125.31C6.A1.205 VH5/VL4, MEB125.31C6.A1.205 VH5/VL3, 15A6 variable heavy chain and variable light chain, 22G2 variable heavy chain and variable light chain, 11G11 variable heavy chain and variable light chain, 10D7 variable heavy chain and variable light chain, 313R19 variable heavy chain and variable light chain, and etigilimab variable heavy chain and variable light chain. 
     In some embodiments, the targeted anti-TIGIT ABD×scIL10 heterodimeric Fc fusion protein comprises a first monomer comprising from N- to C-terminal: a scIL10, a domain linker, and a first Fc domain; a second monomer comprising from N- to C-terminal: an anti-TIGIT VH domain and a second Fc domain; and an anti-TIGIT VL domain such that the VH domain and VL domain form an anti-TIGIT ABD. In certain embodiments, the targeted anti-TIGIT ABD×scIL10 heterodimeric Fc fusion protein comprises a first monomer comprising from N- to C-terminal: a first Fc domain, a domain linker, and a scIL10; a second monomer comprising from N- to C-terminal: an anti-TIGIT VH domain and a second Fc domain; and an anti-TIGIT VL domain such that the VH domain and VL domain form a non-competing anti-TIGIT ABD. In some instances, the scIL10 comprises two IL-10 monomers. In some instances, the scIL10 comprises two IL-10 monomers covalently attached by a linker. In some embodiments, the anti-TIGIT targeted IL-10 Fc fusion protein is XENP30523, XENP30524, and XENP30525 as depicted in  FIGS. 123A-123B  and in the sequences corresponding to the SEQ ID NOS in the sequence listing. 
     XENP30523 is also referred to as αTIGIT(2A5B4)×huIL10.104. XENP30524 is also referred to as αTIGIT(2A5B4)×huIL10.105. XENP30525 is also referred to as αTIGIT(2A5B4)×huIL10.107. 
     C. Targeted IL10M1-Fc Fusion Formats 
       FIG. 89A - FIG. 89M  depict further embodiments for targeted IL-10 fusions based on the IL10M1-Fc category, herein referred to as the “targeted IL10M1-Fc” category. In some embodiments, the “anti-X×(IL10M1) 1 -heteroFc” format (see, e.g.,  FIG. 89A ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an IL10M1 covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker). In some embodiments, the “anti-X×heteroFc-(IL10M1) 1 ” format (see, e.g.,  FIG. 89B ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a second heterodimeric Fc chain covalently linked via the C-terminus to an IL10M1 (optionally via a domain linker). In some embodiments, the “anti-X×heteroFc-(IL10M1) 1 ” format comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain which is covalently linked via the C-terminus to an IL10M1 (optionally via a domain linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. In some embodiments, the “(anti-X) 2 -heteroFc-(IL10M1)1” format (see, e.g.,  FIG. 89C ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to the N-terminus of a second heterodimeric Fc chain which is covalently linked via the C-terminus to an IL10M1 (optionally via a domain linker). In some embodiments, the “(IL10M1)1-(anti-X) 2 -heteroFc” format (see, e.g.,  FIG. 89D ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an IL10M1 covalently linked, optionally via a linker, to an antigen-binding domain which is covalently linked to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). In some embodiments, the “(anti-X) 2 -central-(IL10M1)1” format (see, e.g.,  FIG. 89E ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to an IL10M1 which is covalently linked to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). In some embodiments, the “anti-X×(IL10M1) 2 -heteroFc” format (see, e.g.,  FIG. 89F ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first IL10M1 covalently attached, optionally via a domain linker, to a second IL10M1 which is covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker). In some embodiments, the “anti-X×heteroFc-(IL10M1) 2 ” format (see, e.g.,  FIG. 89G ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a second heterodimeric Fc chain covalently linked via the C-terminus to a first IL10M1 (optionally via a domain linker) which is covalently attached, optionally via a domain linker, to a second IL10M1. In some embodiments, the “anti-X×heteroFc-(IL10M1) 2 ” format comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain which is covalently linked via the C-terminus to a first IL10M1 (optionally via a domain linker) which is covalently linked, optionally via a domain linker, to a second IL10M1, and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. In some embodiments, the “(anti-X) 2 -heteroFc-(IL10M1) 2 ” format (see, e.g.,  FIG. 89H ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to the N-terminus of a second heterodimeric Fc chain which is covalently linked via the C-terminus to a first IL10M1 (optionally via a domain linker) which is covalently attached, optionally via a domain linker, to a second IL10M1. In some embodiments, the “(IL10M1) 2 -(anti-X) 2 -heteroFc” format (see, e.g.,  FIG. 89I ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first IL10M1 covalently linked, optionally via a linker, to a second IL10M1 which is covalently attached (optionally via a domain linker) to an antigen-binding domain which is covalently linked to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). In some embodiments, the “(anti-X) 2 -central-(IL10M1) 2 ” format (see, e.g.,  FIG. 89J ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently linked to a first IL10M1 which is covalently linked, optionally via a domain linker, to a second IL10M1 which is covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a linker). In some embodiments, the “mAb-(IL10M1) 2 ” format (see, e.g.,  FIG. 89K ) comprises two identical monomers, each monomer comprising an antigen-binding domain covalently linked to the N-terminus of a homodimeric Fc chain which is covalently linked via the C-terminus, optionally via a linker, to an IL10M1. In some embodiments, the “(IL10M1) 2 -mAb” format (see, e.g.,  FIG. 89L ) comprises two identical monomers, each monomer comprising an IL10M1 covalently linked, optionally via a linker, to an antigen-binding domain which is covalently linked to the N-terminus of a homodimeric Fc chain. In some embodiments, the “mAb-central-(IL10M1) 2 ” format (see, e.g.,  FIG. 89M ) comprises two identical monomers, each monomer comprising an antigen-binding domain covalently linked to an IL10M1 which is covalently linked, optionally via a linker, to a homodimeric Fc chain. It should be noted that while the antigen-binding domains are depicted as Fabs, the antigen-binding domain can be any antigen binding molecule as defined herein, such as an scFv. 
     In some embodiments, the targeted IL-10 Fc fusion protein (e.g., targeted anti-CD8×IL10M1 heterodimeric Fc fusion protein) comprises an anti-CD8 ABD covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an IL10M1 covalently attached to the N-terminus of a second heterodimeric Fc chain. In some embodiments, the IL10M1 is covalently attached to the N-terminus of a second heterodimeric Fc chain via a domain linker. In some embodiments, the anti-CD8 ABD comprises the VH and VL combination of OKT8_H2_L1. In some embodiments, the anti-CD8 ABD comprises the VH and VL combination of 1C11B3_H1_L1. In some embodiments, the targeted IL-10 Fc fusion protein is XENP25365 or XENP25366 as depicted in  FIG. 94  and in the sequences corresponding to the SEQ ID NOs in the sequence listing. 
     In some embodiments, the targeted IL-10 Fc fusion protein (e.g., targeted anti-CD8 mAb×(IL10M1) 2  heterodimeric Fc fusion protein) comprises two identical monomers, each monomer comprising an anti-CD8 ABD covalently linked to the N-terminus of a homodimeric Fc chain which is covalently linked via the C-terminus to an IL10M1. In some embodiments, the Fc chain is connected to the IL10M1 via a linker. In some embodiments, each monomer comprises two chains such that the first chain comprises from N- to C-terminus: a VH domain of an anti-CD8 ABD, an Fc domain, an optional linker, and an IL10M1, and the second chain comprises a VL domain of an anti-CD9 ABD. In some embodiments, the anti-CD8 ABD comprises the VH and VL combination of 1C11B3_H1_L1. In some embodiments, the targeted IL-10 Fc fusion protein is XENP26172 as depicted in  FIG. 95  and in the sequences corresponding to the SEQ ID NOs in the sequence listing. 
     D. Targeted SplitIL10-Fc Fusion Formats 
       FIG. 90A - FIG. 90H  depict further embodiments for targeted IL-10 fusions based on the splitIL10-Fc category, herein referred to as the “targeted splitIL10-Fc” category. In some embodiment, the “anti-X×(splitIL10) 1 -heteroFc” format (see, e.g.,  FIG. 90A ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a hIL-10(A-D) domain covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker), and a hIL-10(E-F) domain transfected separately so that it non-covalently interacts with the hIL-10(A-D) domain. In some embodiment, the “anti-X×(splitIL10) 1 -heteroFc” format comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a hIL-10(E-F) domain covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker), and a hIL-10(A-D) domain transfected separately so that it non-covalently interacts with the hIL-10(E-F) domain. In some embodiment, the “(anti-X) 2 × heteroFc-(splitIL10) 1 ” format (see, e.g.,  FIG. 90B ) comprises a first monomer comprising an antigen-binding domain covalently attached to the N-terminus of a first heterodimeric Fc chain which is covalently linked via the C-terminus to a hIL-10(A-D) domain and a second monomer comprising an antigen-binding domain covalently linked to the N-terminus of a second heterodimeric Fc chain covalently linked via the C-terminus to a hIL-10(E-F) domain. In some embodiment, the “(splitIL10) 1 -(anti-X) 2 -heteroFc” format (see, e.g.,  FIG. 90C ) comprises a first monomer comprising an hIL-10(A-D) domain covalently attached to an antigen-binding domain which is covalently attached to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an hIL-10(E-F) domain covalently attached to an antigen-binding domain which is covalently attached to the N-terminus of a second heterodimeric Fc chain. In some embodiment, the “(anti-X) 2 -central-(splitIL10) 1 -heteroFc” format (see, e.g.,  FIG. 90D ) comprises a first monomer comprising an antigen-binding domain covalently attached to a hIL-10(A-D) domain which is covalently attached to a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently attached to a hIL-10(E-F) domain which is covalently attached to a second heterodimeric Fc chain. In some embodiment, the “anti-X×(splitIL10)2-heteroFc” format (see, e.g.,  FIG. 90E ) comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first hIL-10(A-D) domain covalently attached to a second hIL-10(A-D) domain which is covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker), and a first hIL-10(E-F) domain covalently attached to a second hIL-10(E-F) domain transfected separately so that they non-covalently interacts with the hIL-10(A-D) domains. In some embodiment, the “anti-X×(splitIL10)2-heteroFc” format comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first hIL-10(E-F) domain covalently attached to a second hIL-10(E-F) domain which is covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker), and a first hIL-10(A-D) domain covalently attached to a second hIL-10(A-D) domain transfected separately so that they non-covalently interact with the hIL-10(E-F) domains. In some embodiment, the “(anti-X) 2 × heteroFc-(splitIL10) 2 ” format (see, e.g.,  FIG. 90F ) comprises a first monomer comprising an antigen-binding domain covalently attached to the N-terminus of a first heterodimeric Fc chain which is covalently linked via the C-terminus to a first hIL-10(A-D) domain covalently attached to a second hIL-10(A-D) domain and a second monomer comprising an antigen-binding domain covalently linked to the N-terminus of a second heterodimeric Fc chain covalently linked via the C-terminus to a first hIL-10(E-F) domain covalently attached to a second hIL-10(E-F) domain. In some embodiment, the “(splitIL10)2-(anti-X) 2 -heteroFc” format (see, e.g.,  FIG. 90G ) comprises a first monomer comprising a first hIL-10(A-D) domain covalently attached to a second hIL-10(A-D) domain which is covalently attached to an antigen-binding domain which is covalently attached to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a first hIL-10(E-F) domain covalently attached to a second hIL-10(E-F) domain which is covalently attached to an antigen-binding domain which is covalently attached to the N-terminus of a second heterodimeric Fc chain. In some embodiment, the “(anti-X) 2 -central-(splitIL10)2-heteroFc” format (see, e.g.,  FIG. 90H ) comprises a first monomer comprising an antigen-binding domain covalently attached to a first hIL-10(A-D) domain which is covalently attached to a second hIL-10(A-D) domain which is covalently attached to a first heterodimeric Fc chain and a second monomer comprising an antigen-binding domain covalently attached to a first hIL-10(E-F) domain which is covalently attached to a second hIL-10(E-F) domain which is covalently attached to a second heterodimeric Fc chain. 
     E. Additional Targeted IL10 Containing Fc Fusion Formats 
     In some embodiments of the (anti-X) 2 -central-scIL10 format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a second antigen binding domain, a second Fc domain, a first protein domain and a second protein domain, wherein the first protein domain is covalently attached to the second protein domain, wherein the second protein domain is covalently attached to the N-terminus of the second Fc domain, and wherein the first protein domain is covalent attached to the second antigen binding domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first protein domain comprises a first IL-10 monomer and the second protein domain comprises a second IL-10 monomer. 
     In some embodiments of the scIL10-(anti-X) 2 -heteroFc format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a second antigen binding domain, a second Fc domain, a first protein domain and a second protein domain, wherein the second antigen binding domain is covalently attached to the N-terminus of the second Fc domain, wherein the first protein domain is covalently attached to the second protein domain, and wherein the second protein domain is covalently attached to the second antigen binding domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first protein domain comprises a first IL-10 monomer and the second protein domain comprises a second IL-10 monomer. 
     In some embodiments of the scIL10-(anti-X) 2 -heteroFc anti-X×(IL10M1) 1 -heteroFc format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a protein domain and a second Fc domain, wherein the protein domain is covalently attached to the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains and wherein the protein domain comprises an IL-10 monomer domain that comprises an insert peptide. In some embodiments, the protein domain is covalently attached to the N-terminus of the second Fc domain. In some embodiments, the protein domain is covalently attached to the C-terminus of the second Fc domain. 
     In some embodiments of the (anti-X) 2 × heteroFc-(IL10M1) 1  format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain, a first protein domain, and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a second antigen binding domain and a second Fc domain, wherein the second antigen binding domain is covalently attached to the N-terminus of the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the protein domain comprises an IL-10 monomer domain that comprises an insert peptide. 
     In some embodiments, the first protein domain is covalently attached to the C-terminus of the first Fc domain. In some embodiments, the first protein domain is covalently attached to the N-terminus of the first antigen binding domain. 
     In some embodiments of the (anti-X) 2 -central-(IL10M1)1-heteroFc format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain, a first protein domain, and a first Fc domain, wherein the first antigen binding domain is covalently attached to the first protein domain and wherein the first protein domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a second antigen binding domain and a second Fc domain, wherein the second antigen binding domain is covalently attached to the N-terminus of the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the protein domain comprises an IL-10 monomer domain that comprises an insert peptide. 
     In some embodiments of the anti-X×(IL10M1) 2 -heteroFc format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a first protein domain, a second protein domain, and a second Fc domain, wherein the first protein domain is covalently attached to the second protein domain, and wherein the second protein domain is covalently attached to the N-terminus of the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first and second protein domain each comprises an IL-10 monomer that comprises an insert peptide. 
     In some embodiments of the anti-X×heteroFc-(IL10M1) 2  format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain; b) a second Fc domain; and c) a first protein domain and a second protein domain, wherein the first protein domain is covalently attached to the second protein domain, wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first and second protein domain each comprises an IL-10 monomer that comprises an insert peptide. In some embodiments, the first protein domain is covalently attached to the second protein domain, and wherein the second protein domain is covalently attached to the C-terminus of the first Fc domain. In some embodiments, the first protein domain is covalently attached to the second protein domain, and wherein the second protein domain is covalently attached to the C-terminus of the second Fc domain. 
     In some embodiments of the anti-X×heteroFc-(IL10M1) 2  format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain, a first protein domain, a second protein domain, and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain, and wherein the first protein domain is covalently attached to the second protein domain and the second protein domain is covalently attached to the C-terminus of the first Fc domain; and b) a second fusion protein comprising a second antigen binding domain and a second Fc domain, wherein the second antigen binding domain is covalently attached to the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first and second protein domain each comprises an IL-10 monomer domain that comprises an insert peptide. 
     In some embodiments of the anti-X×heteroFc-(IL10M1) 2  format, the heterodimeric Fc fusion protein comprises:) a first fusion protein comprising a first antigen binding domain, a first protein domain, a second protein domain, and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain, and wherein the first protein domain is covalently attached to the second protein domain and the second protein domain is covalently attached to the N-terminus of the first antigen binding domain; and b) a second fusion protein comprising a second antigen binding domain and a second Fc domain, wherein the second antigen binding domain is covalently attached to the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first and second protein domain each comprises an IL-10 monomer domain that comprises an insert peptide. 
     In some embodiments of the anti-X) 2 -central-(IL10M1) 2 -heteroFc format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain, a first protein domain, a second protein domain, and a first Fc domain, wherein the first protein domain is covalently attached to the second protein domain and the second protein domain is covalently attached to the N-terminus of the first Fc domain, and wherein the first antigen binding domain is covalently attached to the N-terminus of the first protein domain; and b) a second fusion protein comprising a second antigen binding domain and a second Fc domain, wherein the second antigen binding domain is covalently attached to the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first and second protein domain each comprises an IL-10 monomer domain that comprises an insert peptide. 
     In some embodiments of the mAb-(IL10M1) 2  format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain, a first protein domain, and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the Fc domain; and b) a second fusion protein comprising a second antigen binding domain, a second Fc domain, and a second protein domain, wherein the second antigen binding domain is covalently attached to the N-terminus of the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first and second protein domain each comprises an IL-10 monomer that comprises an insert peptide. In some embodiments, the first protein domain is covalently attached to the C-terminus of the first Fc domain and the second protein domain is covalently attached to the C-terminus of the second Fc domain. In some embodiments, the first protein domain is covalently attached to the N-terminus of the first antigen binding domain and the second protein domain is covalently attached to the N-terminus of the second antigen binding domain. 
     In some embodiments of the mAb-central-(IL10M1) 2  format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain, a first protein domain, and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first protein domain, and wherein the first protein domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a second antigen binding domain, a second Fc domain, and a second protein domain, wherein the second antigen binding domain is covalently attached to the N-terminus of the second protein domain, and wherein the second protein domain is covalently attached to the N-terminus of the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first and second protein domain each comprises an IL-10 monomer that comprises an insert peptide. 
     In some embodiments of the mAb-central-(IL10M1) 2  format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain, a first protein domain, and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first protein domain, and wherein the first protein domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a second antigen binding domain, a second Fc domain, and a second protein domain, wherein the second antigen binding domain is covalently attached to the N-terminus of the second protein domain, and wherein the second protein domain is covalently attached to the N-terminus of the second Fc domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first and second protein domain each comprises an IL-10 monomer that comprises an insert peptide. 
     In some embodiments of the anti-X×(splitIL10)1-heteroFc format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a second Fc domain and a first protein domain, wherein the second Fc domain is covalently attached to the first protein domain; wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first protein domain comprises helices (A-D) of human IL-10. In some embodiments, the heterodimeric Fc fusion protein further comprises a second protein domain non-covalently attached to the first protein domain. In some embodiments, the second protein domain comprises helices (E-F) of human IL-10. 
     In some embodiments of the (anti-X) 2 × heteroFc-(splitIL10)1 format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first protein domain, a first antigen binding domain and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a second protein domain, a second antigen binding domain, and a second Fc domain, wherein the second antigen binding domain is covalently attached to the N-terminus of the second Fc domain, wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first protein domain is a human IL-10(A-D) domain and the second protein domain is a human IL-10(E-F) domain. In some embodiments, the first protein domain is covalently attached to the C-terminus of the first Fc domain and the second protein domain is covalently attached to the C-terminus of the second Fc domain. In some embodiments, the first protein domain is covalently attached to the N-terminus of the first antigen binding domain and the second protein domain is covalently attached to the N-terminus of the second antigen binding domain. 
     In some embodiments of the (anti-X) 2 -central-(splitIL10) 1 -hetero Fc format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first protein domain, a first antigen binding domain and a first Fc domain, wherein the first antigen binding domain is covalently attached to the first protein domain, and the first protein domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a second protein domain, a second antigen binding domain, and a second Fc domain, wherein the second antigen binding domain is covalently attached to the second protein domain, and the second protein domain is covalently attached to the N-terminus of the second Fc domain, wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first protein domain is a human IL-10(A-D) domain and the second protein domain is a human IL-10(E-F) domain. 
     In some embodiments of the anti-X×(splitIL10) 2 -heteroFc format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first antigen binding domain and a first Fc domain, wherein the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain; and b) a second fusion protein comprising a first protein domain, and a second protein domain, and a second Fc domain, wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first protein domain comprises a first human IL-10(A-D) sequence covalently attached to a second human IL-10(A-D) sequence and the second protein domain comprises a first human IL-10(E-F) sequence covalently attached to a second human IL-10(E-F) sequence. In some embodiments, the first protein domain is covalently attached to the second Fc domain and the second protein domain is non-covalently attached to the first protein domain. In some embodiments, the second protein domain is covalently attached to the second Fc domain and the first protein domain is non-covalently attached to the second protein domain. 
     In some embodiments of the anti-X) 2 × heteroFc-(splitIL10)2 format, the heterodimeric Fc fusion protein comprises: a) a first fusion protein comprising a first protein domain, a first antigen binding domain and a first Fc domain; and b) a second fusion protein comprising a second protein domain, a second antigen binding domain, and a second Fc domain, wherein the first and the second Fc domains comprise modifications promoting heterodimerization of the first and the second Fc domains, and wherein the first protein domain comprises a first human IL-10(A-D) sequence covalently attached to a second human IL-10(A-D) sequence and the second protein domain comprises a first human IL-10(E-F) sequence covalently attached to a second human IL-10(E-F) sequence. In some embodiments, the first protein domain is covalently attached to the C-terminus of the first Fc domain and the second protein domain is covalently attached to the C-terminus of the second Fc domain. In some embodiments, the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain and the first protein domain is covalently attached to the N-terminus of the first antigen binding domain, and wherein the second antigen binding domain is covalently attached to the N-terminus of the second Fc domain and the second protein domain is covalently attached to the N-terminus of the second antigen binding domain. In some embodiments, the first protein domain is covalently attached to the N-terminus of the first Fc domain and the second protein domain is covalently attached to the N-terminus of the second Fc domain, and wherein the first antigen binding domain is covalently attached to the N-terminus of the first protein domain and the second antigen binding domain is covalently attached to the N-terminus of the second protein domain. 
     In some embodiments of the mAb-IL10 format, the dimeric Fc fusion protein comprises: (a) a first fusion protein comprising a first IL-10 monomer domain, a first Fc domain, and a first antigen binding domain, wherein the first IL-10 monomer domain is covalently attached to the C-terminus of the first Fc domain, and the first antigen binding domain is covalently attached to the N-terminus of the first Fc domain; and (b) a second fusion protein comprising a second IL-10 monomer domain, a second Fc domain, and a second antigen binding domain, wherein the second IL-10 monomer domain is covalently attached to the C-terminus of the second Fc domain, and the second antigen binding domain is covalently attached to the N-terminus of the second Fc domain. In some embodiments, the first IL-10 monomer domain is attached to the first Fc domain using a first domain linker and/or the second IL-10 monomer domain is attached to the second Fc domain using a second domain linker. In some embodiments, the first antigen binding domain is attached to the first Fc domain using a third domain linker and/or the second antigen binding domain is attached to the second Fc domain using a fourth domain linker. In some embodiments, the first Fc domain and/or second Fc domain comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. In some embodiments, the first and/or the second IL-10 monomer domain comprises a leucine at position 109. In some embodiments, the first and/or the second IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO:4 (human IL-10 (109L) mature form sequence). In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain is a variant IL-10 monomer domain. In some embodiments, the variant IL-10 monomer domain comprises an IL-10 monomer domain with one or more amino acid substitutions resulting in altered affinity for an IL-10 receptor, altered potency, altered potential for deamidation, altered potential for aspartic acid isomerization, altered potential for degradation-related PTMs, altered potential degradation sites, altered disulfide bridges, and/or altered potential N-glycosylation sites. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications at amino acid residues selected from the group consisting of N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, and E151. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications selected from the group consisting of N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, and E151Q. 
     In some embodiments of the IL10mAb format, the dimeric Fc fusion protein comprises: (a) a first fusion protein comprising a first IL-10 monomer domain, a first Fc domain, and a first antigen binding domain, wherein the first IL-10 monomer domain is covalently attached to the first antigen binding domain and the first antigen binding domain is further covalently attached to the N-terminus of the first Fc domain; and (b) a second fusion protein comprising a second IL-10 monomer domain, a second Fc domain, and a second antigen binding domain, wherein the second IL-10 monomer domain is covalently attached to the second antigen binding domain and the second antigen binding domain is covalently attached to the N-terminus of the second Fc domain. In some embodiments, the first IL-10 monomer domain is attached to the first antigen binding domain using a first domain linker and/or the second IL-10 monomer domain is attached to the second antigen binding domain using a second domain linker. In some embodiments, the first antigen binding domain is attached to the first Fc domain using a third domain linker and/or the second antigen binding domain is attached to the second Fc domain using a fourth domain linker. In some embodiments, the first and/or second Fc domains comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. In some embodiments, the first and/or the second IL-10 monomer domain comprises a histidine at position 109. In some embodiments, the first and/or the second IL-10 monomer domain comprises a leucine at position 109. In some embodiments, the first and/or the second IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO:4 (human IL-10 (109L) mature form sequence). In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain is a variant IL-10 monomer domain. In some embodiments, the variant IL-10 monomer domain comprises an IL-10 monomer domain with one or more amino acid substitutions resulting in altered affinity for an IL-10 receptor, altered potency, altered potential for deamidation, altered potential for aspartic acid isomerization, altered potential for degradation-related PTMs, altered potential degradation sites, altered disulfide bridges, and/or altered potential N-glycosylation sites. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications at amino acid residues selected from the group consisting of N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, and E151. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications selected from the group consisting of N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, and E151Q. 
     In some embodiments of the mAb-central-IL10 format, the dimeric Fc fusion protein comprises: (a) a first fusion protein comprising a first IL-10 monomer domain, a first Fc domain, and a first antigen binding domain, wherein the first IL-10 monomer domain is covalently attached to the first antigen binding domain and the first IL-10 monomer domain is further covalently attached to the N-terminus of the first Fc domain; and (b) a second fusion protein comprising a second IL-10 monomer domain, a second Fc domain, and a second antigen binding domain, wherein the second IL-10 monomer domain is covalently attached to the second antigen binding domain and the second IL-10 monomer domain is covalently attached to the N-terminus of the second Fc domain. 
     In some embodiments, the first IL-10 monomer domain is attached to the first antigen binding domain using a first domain linker and/or the second IL-10 monomer domain is attached to the second antigen binding domain using a second domain linker. In some embodiments, the first IL-10 monomer domain is attached to the first Fc domain using a third domain linker and/or the second IL-10 monomer domain is attached to the second Fc domain using a fourth domain linker. In some embodiments, the first and/or second Fc domains comprise a further amino acid substitution selected from the group consisting of M428L, N434S, and M428L/N434S, according to EU numbering. In some embodiments, the first and/or the second IL-10 monomer domain comprises a histidine at position 109. In some embodiments, the first and/or the second IL-10 monomer domain comprises a leucine at position 109. In some embodiments, the first and/or the second IL-10 monomer domain comprises a polypeptide sequence selected from the group consisting of SEQ ID NO:1 (human IL-10 (109H) precursor sequence), SEQ ID NO:2 (human IL-10 (109L) precursor sequence), SEQ ID NO:3 (human IL-10 (109H) mature form sequence), SEQ ID NO:4 (human IL-10 (109L) mature form sequence). In some embodiments, the first IL-10 monomer domain and/or the second IL-10 monomer domain is a variant IL-10 monomer domain. In some embodiments, the variant IL-10 monomer domain comprises an IL-10 monomer domain with one or more amino acid substitutions resulting in altered affinity for an IL-10 receptor, altered potency, altered potential for deamidation, altered potential for aspartic acid isomerization, altered potential for degradation-related PTMs, altered potential degradation sites, altered disulfide bridges, and/or altered potential N-glycosylation sites. the variant IL-10 monomer domain comprises one or more amino acid modifications at amino acid residues selected from the group consisting of N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, and E151. In some embodiments, the variant IL-10 monomer domain comprises one or more amino acid modifications selected from the group consisting of N21D, D28N, Q38E, M39T, D41N, Q42E, L43V, D44N, N45D, I87A, E142Q, D144N, and E151Q. 
     As will be appreciated, the antigen binding domain for any of the formats described herein, including those illustrated in the figures including but not limited to  FIGS. 87A-87D ,  FIGS. 88A-88E ,  FIGS. 89A-89M , and  FIGS. 90A-90H  may be directed to any suitable antigen, including without limitation CD8, NKG2D, PD-1, and TIGIT. In some embodiments, any of antigen binding domain (e.g., a first and/or a second antigen binding domain) described herein that binds CD8 is incorporated into a targeted IL-10 fusion protein format. The sequence of exemplary CD8 ABDs are provided in  FIG. 92  and the sequence listing. In some embodiments, any of antigen binding domain (e.g., a first and/or a second antigen binding domain) described herein that binds NKG2D is incorporated into a targeted format. Sequences of exemplary NKG2D ABDs are provided in  FIGS. 93A-93C  and the sequence listing. In some embodiments, any of antigen binding domain (e.g., a first and/or a second antigen binding domain) described herein that binds PD-1 is incorporated into a targeted format. Sequences of exemplary PD-1 ABDs are provided in  FIGS. 100A-100G  and the sequence listing. Sequences of exemplary non-competing PD-1 ABDs are provided in  FIGS. 104A-104B  and the sequence listing. In some embodiments, any of antigen binding domain (e.g., a first and/or a second antigen binding domain) described herein that binds TIGIT is incorporated into a targeted format. Sequences of exemplary TIGIT ABDs are provided in  FIGS. 122A-122C  and the sequence listing. 
     In another aspect of the targeted formats described herein, any of the IL-10 monomer domains (e.g., the variant IL-10 monomer domain) described herein (e.g., those shown in  FIGS. 55, 57, 64, 67, 70A-70B, and 73 , and the corresponding SEQ ID NOs) are useful for an applicable targeted IL-10 fusion protein format. In some embodiments, any of the hIL-10(A-D) and hIL-10(E-F) sequences including but not limited to SEQ ID NO:21 and 22, respectively of a splitIL10 and he hIL-10(A-D) and hIL-10(E-F) variants described herein (e.g., those shown in  FIGS. 55, 57, 64, 67, 70A-70B, and 73 , and the corresponding SEQ ID NOs) are useful in a targeted IL-10 fusion protein format. In certain embodiments, any of the IL10M1 sequences including but not limited to SEQ ID NO:24 and the IL10M1 variants described herein (e.g., those shown in  FIGS. 36A-36E, 55, 57, 64, 67, 70A-70B, 71A-71E, 73, 74A-74B, 75A-75B, and 76A-76D , and the corresponding SEQ ID NOs) are useful in a targeted IL-10 fusion protein format. In some embodiments, any of the IL10M1 sequences comprise an amino acid sequence having at least 90% (e.g., at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more) sequence identity to SEQ ID NO:24. In some embodiments, any of the scIL10 sequences including but not limited to SEQ ID NO:23 and the scIL10 variants described herein (e.g., those shown in  FIGS. 21A-21C, 22, 35A-35D, 39A-39G, 40A-40M, 41A-41F, 48, 49A-49B, 53, 55, 56A-56C ,  58 ,  59 A- 59 H,  60 ,  64 ,  65 A- 65 B,  66 A- 66 D,  67 ,  68 ,  69 ,  70 A- 70 B,  73 ,  78 A- 78 G,  79 A- 79 G, and  86 A- 86 D, and the corresponding SEQ ID NOs) are useful in a targeted IL-10 fusion protein format. In some embodiments, any of the scIL10 sequences comprise an amino acid sequence having at least 90% (e.g., at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more) sequence identity to SEQ ID NO:23. 
     In one aspect, provided herein is a composition comprising any one of the heterodimeric Fc fusion proteins or dimeric fusion proteins outlined herein including the figures for use in treating cancer in a subject. Also provided is one or more nucleic acids encoding such a heterodimeric Fc fusion protein or dimeric fusion protein. Also provided is a host cell comprising one or more of such nucleic acids encoding a heterodimeric Fc fusion protein or dimeric fusion protein described herein. 
     In another aspect, provided herein is a method of producing any of the heterodimeric Fc fusion proteins or dimeric fusion proteins described. In some embodiments, the method comprises culturing any of the host cells outlined herein under conditions whereby the heterodimeric Fc fusion protein or dimeric fusion protein is produced; and recovering the protein. 
     VIII. Useful Embodiments of the Invention 
     As will be appreciated by those in the art and discussed more fully below, the untargeted IL-10 fusion proteins of the present invention can take on a wide variety of configurations, as are generally depicted in the figures including, but not limited to,  FIGS. 16A-16D, 20A-20B, 23A-23F, and 29A-29D . The targeted IL-10 fusion proteins of the present invention can take on a wide variety of configurations, as are generally depicted in the figures including, but not limited to,  FIGS. 87A-87D, 88A-88D, 89A-89M, and 90A-90H . 
     In one embodiment of the invention is the scIL10-heteroFc format depicted in  FIG. 20A  with IL-10 variants and/or amino acid substitutions in the Fc domain. In general, such a format comprises a first monomer/fusion protein comprising an scIL-10 covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a domain linker) and a second monomer/fusion protein comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. In such an embodiment, the scIL-10 comprises a first IL-10 monomer domain attached to a second IL-10 monomer domain. 
     In further embodiments, the Fc fusion proteins in this exemplary format have the sequences set forth in  FIGS. 78B, 78C, and 78F  for XENP30005 (SEQ ID NOS:25 and 26), XENP30008 (SEQ ID NOS: 27 and 28) or XENP30013 (SEQ ID NOS: 29 and 30), respectively. In still further embodiments, the Fc fusion proteins in this exemplary format comprise the sequences set forth in  FIGS. 78B, 78C, and 78F  for XENP30005 (SEQ ID NOS:25 and 26), XENP30008 (SEQ ID NOS: 27 and 28) or XENP30013 (SEQ ID NOS: 29 and 30), respectively with the additional amino acid modifications selected from the group (singly or in any combination): G445del, K447del, G445del/K447del, M428L, N434S, and M428L/N434S, according to EU numbering. 
     In some embodiments, the scIL10-heteroFc format fusion protein of the invention comprises an IL-10 monomer comprising any of the human IL10 precursor or mature sequences (109H or 109L) depicted in  FIG. 1  within the scIL10-heteroFc format depicted in  FIG. 20A . In further embodiments, the IL-10 monomer comprises IL-10 monomer variants designed with the aim to reduce their affinity for the IL-10 receptor complex and/or to reduce their potency. In such affinity/potency variants, variant IL-10 monomers may contain one or more substitutions at positions selected from: N21, D28, Q38, M39, D41, Q42, L43, D44, N45, I87, E142, D144, and E151, singly or in any combination. Exemplary sequences for variant IL-10 monomers are shown in  FIGS. 35A-35C —as will be appreciated, although the sequences depicted are in the context of the IL-10 (109L) sequence, the same substitutions can be made in the context of the IL-10(109H) sequence. Any of the sequences depicted in  FIGS. 35A-35C  can be used in the context of the scIL10-heteroFc format depicted in  FIG. 20A . 
     In some embodiments, the scIL10-heteroFc format fusion protein of the present invention includes modifications in the Fc domain that improve manufacturability. In further embodiments, the scIL10-heteroFc format fusion protein of the invention includes the G446del/K4447del modification in the Fc region of one or both Fc domains. In further embodiments, the scIL10-heteroFc format fusion protein of the invention includes both the G446del/K4447del modification and the M428L/N434S modification in one or both of the Fc domains. 
     In further embodiments, the scIL10-heteroFc format fusion protein of the present invention includes domain linkers between the first and second IL-10 monomer domain and/or between the scIL10 and the Fc domain. In still further embodiments, the domain linker used is selected from those pictured in the figures. In yet further embodiments, the scIL-10 complexes comprising domain linkers between the first IL-10 monomer and the second IL-10 monomer includes sequences as depicted in  FIG. 48 , including SEQ ID NO: 367 (scIL-10(G 4 S)), SEQ ID NO: 368 (scIL-10(G 4 S) 2 ), or SEQ ID NO: 369 (scIL-10(G 4 S) 3 ). 
     In still further embodiments, scIL10-heteroFc format fusion protein of the present invention comprising domain linkers between the first and second IL-10 monomers have sequences as depicted in  FIGS. 49A-49B . In yet further embodiments, the proteins are selected from XENP25239, XENP25240, and XENP25241. 
     In one aspect, the present invention provides IL-10 fusion proteins in the “anti-X×scIL10-heteroFc” format pictured in  FIG. 87A , which comprises a first fusion protein comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second fusion protein comprising a scIL-10 covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker). 
     In one embodiment, the antigen-binding domain used in the anti-X×scIL10-heteroFc format is directed to a target including without limitation CD8, NKG2D, PD-1, and TIGIT. 
     In embodiments of the anti-X×scIL10-heteroFc format in which the anti-X (antigen binding domain) binds to PD-1, illustrative sequences for such formats are provided in  FIGS. 98-100G . In further embodiments, the PD-1 ABD sequence used in the anti-X×scIL10-heteroFc format is a humanized anti-PD1 ABD. In still further embodiments, the humanized anti-PD1 ABD comprises a variable heavy chain sequence according to any set forth in  FIGS. 100A-100G  and the sequence listing for the corresponding SEQ ID NOS. In yet further embodiments, the humanized anti-PD1 ABD comprises a variable light chain sequence according to any set forth in  FIGS. 100A-100G  and the sequence listing for the corresponding SEQ ID NOS. In some embodiments, the humanized anti-PD1 ABD comprises a variable heavy chain sequence and a variable light chain sequence according to any set forth in  FIGS. 100A-100G  and the sequence listing for the corresponding SEQ ID NOS. In still further embodiments, the humanized non-competing anti-PD1 ABD comprises a variable heavy chain sequence according to any set forth in  FIGS. 104A-104B  and the sequence listing for the corresponding SEQ ID NOS. In yet further embodiments, the humanized non-competing anti-PD1 ABD comprises a variable light chain sequence according to any set forth in  FIGS. 104A-104B  and the sequence listing for the corresponding SEQ ID NOS. In some embodiments, the humanized non-competing anti-PD1 ABD comprises a variable heavy chain sequence and a variable light chain sequence according to any set forth in  FIGS. 104A-104B  and the sequence listing for the corresponding SEQ ID NOS. In further embodiments, the humanized non-competing anti-PD1 ABD is combined in the anti-X×scIL10-heteroFc format with either or both the first and second Fc domains containing the M428L/N434S modification. In still further embodiments, the humanized anti-PD1 is combined in the anti-X×scIL10-heteroFc format with either or both the first and second Fc domains containing the M428L/N434S modification. In yet further embodiments, the anti-X×scIL10-heteroFc format fusion proteins of the invention are XENP25953, XENP27830, and XENP27831. 
     In embodiments of the anti-X×scIL10-heteroFc format in which the anti-X (antigen binding domain) binds to TIGIT, illustrative sequences for such formats are provided in  FIGS. 98-100G . In some embodiments, the TIGIT ABD sequence used in the anti-X×scIL10-heteroFc format is a humanized anti-TIGIT ABD. In still further embodiments, the humanized anti-TIGIT ABD comprises a variable heavy chain sequence according to any set forth in  FIGS. 122A-122C  and the sequence listing for the corresponding SEQ ID NOS. In yet further embodiments, the humanized anti-TIGIT ABD comprises a variable light chain sequence according to any set forth in  FIGS. 122A-122C  and the sequence listing for the corresponding SEQ ID NOS. In some embodiments, the humanized anti-TIGIT ABD comprises a variable heavy chain sequence and a variable light chain sequence according to any set forth in  FIGS. 122A-122C  and the sequence listing for the corresponding SEQ ID NOS. In further embodiments, the humanized anti-TIGIT ABD is combined in the anti-X×scIL10-heteroFc format with either or both the first and second Fc domains containing the M428L/N434S modification. In yet further embodiments, the anti-X×scIL10-heteroFc format fusion proteins of the invention are XENP30523, XENP30524, and XENP30525. 
     In embodiments of the anti-X×scIL10-heteroFc format in which the anti-X (antigen binding domain) binds to CD8, illustrative sequences for such formats are provided in  FIGS. 98-100G . In some embodiments, the CD8 ABD sequence used in the anti-X×scIL10-heteroFc format is a humanized anti-CD8 ABD. In still further embodiments, the humanized anti-CD8 ABD comprises a variable heavy chain sequence according to any set forth in  FIG. 92  and the sequence listing for the corresponding SEQ ID NOS. In yet further embodiments, the humanized anti-CD8 ABD comprises a variable light chain sequence according to any set forth in  FIG. 92  and the sequence listing for the corresponding SEQ ID NOS. In some embodiments, the humanized anti-CD8 ABD comprises a variable heavy chain sequence and a variable light chain sequence according to any set forth in  FIG. 92  and the sequence listing for the corresponding SEQ ID NOS. In further embodiments, the humanized anti-CD8 ABD is combined in the anti-X×scIL10-heteroFc format with either or both the first and second Fc domains containing the M428L/N434S modification. In yet further embodiments, the anti-X×scIL10-heteroFc format fusion proteins of the invention are XENP25365, XENP25366, and XENP30525. 
     In embodiments of the anti-X×scIL10-heteroFc format in which the anti-X (antigen binding domain) binds to NKG2D, illustrative sequences for such formats are provided in  FIGS. 98-100G . In some embodiments, the NKG2D ABD sequence used in the anti-X×scIL10-heteroFc format is a humanized anti-NKG2D ABD. In still further embodiments, the humanized anti-NKG2D ABD comprises a variable heavy chain sequence according to any set forth in  FIGS. 93A-93C  and the sequence listing for the corresponding SEQ ID NOS. In yet further embodiments, the humanized anti-NKG2D ABD comprises a variable light chain sequence according to any set forth in  FIGS. 93A-93C  and the sequence listing for the corresponding SEQ ID NOS. In some embodiments, the humanized anti-NKG2D ABD comprises a variable heavy chain sequence and a variable light chain sequence according to any set forth in  FIGS. 93A-93C  and the sequence listing for the corresponding SEQ ID NOS. In further embodiments, the humanized anti-NKG2D ABD is combined in the anti-X×scIL10-heteroFc format with either or both the first and second Fc domains containing the M428L/N434S modification. In yet further embodiments, the anti-X×scIL10-heteroFc format fusion proteins of the invention are XENP25953, XENP30526, XENP30527, XENP30528, and XENP31819. 
     IX. Nucleic Acids of the Invention 
     The invention further provides nucleic acid compositions encoding the Fc fusion proteins, the IL-10 monomer domains, and the IL-10 dimeric complexes of the invention (or, in the case of a monomer Fc domain protein, nucleic acids encoding those as well). 
     As will be appreciated by those in the art, the nucleic acid compositions will depend on the format of the fusion protein. Thus, for example, when the format requires three amino acid sequences, three nucleic acid sequences can be incorporated into one or more expression vectors for expression. Similarly for some formats, only two nucleic acids are needed; again, they can be put into one or two expression vectors. 
     As is known in the art, the nucleic acids encoding the components of the invention can be incorporated into expression vectors as is known in the art, and depending on the host cells used to produce the heterodimeric Fc fusion proteins of the invention. Generally the nucleic acids are operably linked to any number of regulatory elements (promoters, origin of replication, selectable markers, ribosomal binding sites, inducers, etc.). The expression vectors can be extra-chromosomal or integrating vectors. 
     The nucleic acids and/or expression vectors of the invention are then transformed into any number of different types of host cells as is well known in the art, including mammalian, bacterial, yeast, insect and/or fungal cells, with mammalian cells (e.g. CHO cells), finding use in many embodiments. 
     In some embodiments, nucleic acids encoding each monomer, as applicable depending on the format, are each contained within a single expression vector, generally under different or the same promoter controls. In embodiments of particular use in the present invention, each of these two or three nucleic acids are contained on a different expression vector. 
     The Fc fusion protein of the invention are made by culturing host cells comprising the expression vector(s) as is well known in the art. Once produced, traditional fusion protein or antibody purification steps are done, including an ion exchange chromotography step. As discussed herein, having the pIs of the two monomers differ by at least 0.5 can allow separation by ion exchange chromatography or isoelectric focusing, or other methods sensitive to isoelectric point. That is, the inclusion of pI substitutions that alter the isoelectric point (pI) of each monomer so that each monomer has a different pI and the heterodimer also has a distinct pI, thus facilitating isoelectric purification of the heterodimer (e.g., anionic exchange chromatography, cationic exchange chromatography). These substitutions also aid in the determination and monitoring of any contaminating homodimers post-purification (e.g., IEF gels, cIEF, and analytical IEX columns). 
     X. Biological and Biochemical Functionality of IL-10 Immunomodulatory Fc Fusion Proteins 
     Generally the Fc fusion proteins of the invention are administered to patients with cancer, and efficacy is assessed, in a number of ways as described herein. Thus, while standard assays of efficacy can be run, such as cancer load, size of tumor, evaluation of presence or extent of metastasis, etc., immuno-oncology treatments can be assessed on the basis of immune status evaluations as well. This can be done in a number of ways, including both in vitro and in vivo assays. For example, evaluation of changes in immune status (e.g., presence of ICOS+CD4+ T cells following ipi treatment) along with “old fashioned” measurements such as tumor burden, size, invasiveness, LN involvement, metastasis, etc. can be done. Thus, any or all of the following can be evaluated: the inhibitory effects of PVRIG on CD4 +  T cell activation or proliferation, CD8 +  T (CTL) cell activation or proliferation, CD8 +  T cell-mediated cytotoxic activity and/or CTL mediated cell depletion, NK cell activity and NK mediated cell depletion, the potentiating effects of PVRIG on Treg cell differentiation and proliferation and Treg- or myeloid derived suppressor cell (MDSC)-mediated immunosuppression or immune tolerance, and/or the effects of PVRIG on proinflammatory cytokine production by immune cells, e.g., IL-2, IFN-γ or TNF-α production by T or other immune cells. 
     In some embodiments, assessment of treatment is done by evaluating immune cell proliferation, using for example, CFSE dilution method, Ki67 intracellular staining of immune effector cells, and  3 H-thymidine incorporation method, 
     In some embodiments, assessment of treatment is done by evaluating the increase in gene expression or increased protein levels of activation-associated markers, including one or more of: CD25, CD69, CD137, ICOS, PD1, GITR, OX40, and cell degranulation measured by surface expression of CD107A. 
     In general, gene expression assays are done as is known in the art. 
     In general, protein expression measurements are also similarly done as is known in the art. 
     In some embodiments, assessment of treatment is done by assessing cytotoxic activity measured by target cell viability detection via estimating numerous cell parameters such as enzyme activity (including protease activity), cell membrane permeability, cell adherence, ATP production, co-enzyme production, and nucleotide uptake activity. Specific examples of these assays include, but are not limited to, Trypan Blue or PI staining,  51 Cr or  35 S release method, LDH activity, MTT and/or WST assays, Calcein-AM assay, Luminescent based assay, and others. 
     In some embodiments, assessment of treatment is done by assessing T cell activity measured by cytokine production, measure either intracellularly in culture supernatant using cytokines including, but not limited to, IFNγ, TNFα, GM-CSF, IL2, IL6, IL4, IL5, IL10, IL13 using well known techniques. 
     Accordingly, assessment of treatment can be done using assays that evaluate one or more of the following: (i) increases in immune response, (ii) increases in activation of αβ and/or γδ T cells, (iii) increases in cytotoxic T cell activity, (iv) increases in NK and/or NKT cell activity, (v) alleviation of αβ and/or γδ T-cell suppression, (vi) increases in pro-inflammatory cytokine secretion, (vii) increases in IL-2 secretion; (viii) increases in interferon-γ production, (ix) increases in Th1 response, (x) decreases in Th2 response, (xi) decreases or eliminates cell number and/or activity of at least one of regulatory T cells (Tregs). 
     A. Assays to Measure Efficacy and Potency 
     In some embodiments, T cell activation is assessed using a Mixed Lymphocyte Reaction (MLR) assay as is known in the art. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in immune response as measured for an example by phosphorylation or de-phosphorylation of different factors, or by measuring other post translational modifications. IL-12 mediates IFNγ expression and secretion through phosphorylation of STAT4 (Morinobu et al., 2002). Accordingly, in a preferred embodiment, the signaling pathway assay measures increases or decreases in immune response as indicated by phosphorylation of STAT4. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in activation of αβ and/or γδ T cells as measured for an example by cytokine secretion or by proliferation or by changes in expression of activation markers like for an example CD137, CD107a, PD1, etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in cytotoxic T cell activity as measured for an example by direct killing of target cells like for an example cancer cells or by cytokine secretion or by proliferation or by changes in expression of activation markers like for an example CD137, CD107a, PD1, etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in NK and/or NKT cell activity as measured for an example by direct killing of target cells like for an example cancer cells or by cytokine secretion or by changes in expression of activation markers like for an example CD107a, etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in αβ and/or γδ T-cell suppression, as measured for an example by cytokine secretion or by proliferation or by changes in expression of activation markers like for an example CD137, CD107a, PD1, etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in pro-inflammatory cytokine secretion as measured for example by ELISA or by Luminex or by Multiplex bead based methods or by intracellular staining and FACS analysis or by Alispot etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in IL-2 secretion as measured for example by ELISA or by Luminex or by Multiplex bead based methods or by intracellular staining and FACS analysis or by Alispot etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in interferon-γ production as measured for example by ELISA or by Luminex or by Multiplex bead based methods or by intracellular staining and FACS analysis or by Alispot etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in Th1 response as measured for an example by cytokine secretion or by changes in expression of activation markers. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in Th2 response as measured for an example by cytokine secretion or by changes in expression of activation markers. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases cell number and/or activity of at least one of regulatory T cells (Tregs), as measured for example by flow cytometry or by IHC. A decrease in response indicates immunostimulatory activity. Appropriate decreases are the same as for increases, outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in M2 macrophages cell numbers, as measured for example by flow cytometry or by IHC. A decrease in response indicates immunostimulatory activity. Appropriate decreases are the same as for increases, outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in M2 macrophage pro-tumorigenic activity, as measured for an example by cytokine secretion or by changes in expression of activation markers. A decrease in response indicates immunostimulatory activity. Appropriate decreases are the same as for increases, outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in N2 neutrophils increase, as measured for example by flow cytometry or by IHC. A decrease in response indicates immunostimulatory activity. Appropriate decreases are the same as for increases, outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in N2 neutrophils pro-tumorigenic activity, as measured for an example by cytokine secretion or by changes in expression of activation markers. A decrease in response indicates immunostimulatory activity. Appropriate decreases are the same as for increases, outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in inhibition of T cell activation, as measured for an example by cytokine secretion or by proliferation or by changes in expression of activation markers like for an example CD137, CD107a, PD1, etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in inhibition of CTL activation as measured for an example by direct killing of target cells like for an example cancer cells or by cytokine secretion or by proliferation or by changes in expression of activation markers like for an example CD137, CD107a, PD1, etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in αβ and/or γδ T cell exhaustion as measured for an example by changes in expression of activation markers. A decrease in response indicates immunostimulatory activity. Appropriate decreases are the same as for increases, outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases αβ and/or γδ T cell response as measured for an example by cytokine secretion or by proliferation or by changes in expression of activation markers like for an example CD137, CD107a, PD1, etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in stimulation of antigen-specific memory responses as measured for an example by cytokine secretion or by proliferation or by changes in expression of activation markers like for an example CD45RA, CCR7 etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in apoptosis or lysis of cancer cells as measured for an example by cytotoxicity assays such as for an example MTT, Cr release, Calcine AM, or by flow cytometry based assays like for an example CFSE dilution or propidium iodide staining etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in stimulation of cytotoxic or cytostatic effect on cancer cells, as measured for an example by cytotoxicity assays such as for an example MTT, Cr release, Calcine AM, or by flow cytometry based assays like for an example CFSE dilution or propidium iodide staining etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases direct killing of cancer cells as measured for an example by cytotoxicity assays such as for an example MTT, Cr release, Calcine AM, or by flow cytometry based assays like for an example CFSE dilution or propidium iodide staining etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases Th17 activity as measured for an example by cytokine secretion or by proliferation or by changes in expression of activation markers. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, the signaling pathway assay measures increases or decreases in induction of complement dependent cytotoxicity and/or antibody dependent cell-mediated cytotoxicity, as measured for an example by cytotoxicity assays such as for an example MTT, Cr release, Calcine AM, or by flow cytometry based assays like for an example CFSE dilution or propidium iodide staining etc. An increase in activity indicates immunostimulatory activity. Appropriate increases in activity are outlined below. 
     In one embodiment, T cell activation is measured for an example by direct killing of target cells like for an example cancer cells or by cytokine secretion or by proliferation or by changes in expression of activation markers like for an example CD137, CD107a, PD1, etc. For T-cells, increases in proliferation, cell surface markers of activation (e.g., CD25, CD69, CD137, PD1), cytotoxicity (ability to kill target cells), and cytokine production (e.g., IL-2, IL-4, IL-6, IFNγ, TNF-α, IL-10, IL-17A) would be indicative of immune modulation that would be consistent with enhanced killing of cancer cells. 
     In one embodiment, NK cell activation is measured for example by direct killing of target cells like for an example cancer cells or by cytokine secretion or by changes in expression of activation markers like for an example CD107a, etc. For NK cells, increases in proliferation, cytotoxicity (ability to kill target cells and increases CD107a, granzyme, and perforin expression), cytokine production (e.g., IFNγ and TNF), and cell surface receptor expression (e.g. CD25) would be indicative of immune modulation that would be consistent with enhanced killing of cancer cells. 
     In one embodiment, γδ T cell activation is measured for example by cytokine secretion or by proliferation or by changes in expression of activation markers. 
     In one embodiment, Th1 cell activation is measured for example by cytokine secretion or by changes in expression of activation markers. 
     Appropriate increases in activity or response (or decreases, as appropriate as outlined above), are increases of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95% or 98 to 99% percent over the signal in either a reference sample or in control samples, for example test samples that do not contain an IL-12 heterodimeric fusion protein of the invention. Similarly, increases of at least one-, two-, three-, four- or five-fold as compared to reference or control samples show efficacy. 
     XI. Treatments 
     Once made, the compositions of the invention find use in a number of oncology applications, by treating cancer, generally by promoting T cell activation (e.g., T cells are no longer suppressed) with the binding of the heterodimeric Fc fusion proteins of the invention. 
     Accordingly, the heterodimeric compositions of the invention find use in the treatment of these cancers. 
     A. Fusion Protein Compositions for In Vivo Administration 
     Formulations of the fusion proteins used in accordance with the present invention are prepared for storage by mixing a fusion protein having the desired degree of purity with optional pharmaceutically acceptable carriers, excipients or stabilizers (as generally outlined in Remington&#39;s Pharmaceutical Sciences 16th edition, Osol, A. Ed. [1980]), in the form of lyophilized formulations or aqueous solutions. Acceptable carriers, buffers, excipients, or stabilizers are nontoxic to recipients at the dosages and concentrations employed, and include buffers such as phosphate, citrate, and other organic acids; antioxidants including ascorbic acid and methionine; preservatives (such as octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride; benzalkonium chloride, benzethonium chloride; phenol, butyl or benzyl alcohol; alkyl parabens such as methyl or propyl paraben; catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol); low molecular weight (less than about 10 residues) polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, histidine, arginine, or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugars such as sucrose, mannitol, trehalose or sorbitol; salt-forming counter-ions such as sodium; metal complexes (e.g. Zn-protein complexes); and/or non-ionic surfactants such as TWEEN™, PLURONICS™ or polyethylene glycol (PEG). 
     B. Administrative Modalities 
     The fusion proteins and chemotherapeutic agents of the invention are administered to a subject, in accord with known methods, such as intravenous administration as a bolus or by continuous infusion over a period of time. 
     C. Treatment Modalities 
     In the methods of the invention, therapy is used to provide a positive therapeutic response with respect to a disease or condition. By “positive therapeutic response” is intended an improvement in the disease or condition, and/or an improvement in the symptoms associated with the disease or condition. For example, a positive therapeutic response would refer to one or more of the following improvements in the disease: (1) a reduction in the number of neoplastic cells; (2) an increase in neoplastic cell death; (3) inhibition of neoplastic cell survival; (5) inhibition (i.e., slowing to some extent, preferably halting) of tumor growth; (6) an increased patient survival rate; and (7) some relief from one or more symptoms associated with the disease or condition. 
     Positive therapeutic responses in any given disease or condition can be determined by standardized response criteria specific to that disease or condition. Tumor response can be assessed for changes in tumor morphology (i.e., overall tumor burden, tumor size, and the like) using screening techniques such as magnetic resonance imaging (MRI) scan, x-radiographic imaging, computed tomographic (CT) scan, bone scan imaging, endoscopy, and tumor biopsy sampling including bone marrow aspiration (BMA) and counting of tumor cells in the circulation. 
     In addition to these positive therapeutic responses, the subject undergoing therapy may experience the beneficial effect of an improvement in the symptoms associated with the disease. 
     Treatment according to the present invention includes a “therapeutically effective amount” of the medicaments used. A “therapeutically effective amount” refers to an amount effective, at dosages and for periods of time necessary, to achieve a desired therapeutic result. 
     A therapeutically effective amount may vary according to factors such as the disease state, age, sex, and weight of the individual, and the ability of the medicaments to elicit a desired response in the individual. A therapeutically effective amount is also one in which any toxic or detrimental effects of the protein or protein portion are outweighed by the therapeutically beneficial effects. 
     A “therapeutically effective amount” for tumor therapy may also be measured by its ability to stabilize the progression of disease. The ability of a compound to inhibit cancer may be evaluated in an animal model system predictive of efficacy in human tumors. 
     Alternatively, this property of a composition may be evaluated by examining the ability of the compound to inhibit cell growth or to induce apoptosis by in vitro assays known to the skilled practitioner. A therapeutically effective amount of a therapeutic compound may decrease tumor size, or otherwise ameliorate symptoms in a subject. One of ordinary skill in the art would be able to determine such amounts based on such factors as the subject&#39;s size, the severity of the subject&#39;s symptoms, and the particular composition or route of administration selected. 
     Dosage regimens are adjusted to provide the optimum desired response (e.g., a therapeutic response). For example, a single bolus may be administered, several divided doses may be administered over time or the dose may be proportionally reduced or increased as indicated by the exigencies of the therapeutic situation. Parenteral compositions may be formulated in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the subjects to be treated; each unit contains a predetermined quantity of active compound calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. 
     The specification for the dosage unit forms of the present invention are dictated by and directly dependent on (a) the unique characteristics of the active compound and the particular therapeutic effect to be achieved, and (b) the limitations inherent in the art of compounding such an active compound for the treatment of sensitivity in individuals. 
     The efficient dosages and the dosage regimens for the heterodimeric proteins used in the present invention depend on the disease or condition to be treated and may be determined by the persons skilled in the art. 
     An exemplary, non-limiting range for a therapeutically effective amount of an heterodimeric proteins used in the present invention is about 0.1-100 mg/kg. 
     All cited references are herein expressly incorporated by reference in their entirety. 
     Whereas particular embodiments of the invention have been described above for purposes of illustration, it will be appreciated by those skilled in the art that numerous variations of the details may be made without departing from the invention as described in the appended claims. 
     EXAMPLES 
     Examples are provided below to illustrate the present invention. These examples are not meant to constrain the present invention to any particular application or theory of operation. For all constant region positions discussed in the present invention, numbering is according to the EU index as in Kabat (Kabat et al., 1991, Sequences of Proteins of Immunological Interest, 5th Ed., United States Public Health Service, National Institutes of Health, Bethesda, entirely incorporated by reference). Those skilled in the art of antibodies will appreciate that this convention consists of nonsequential numbering in specific regions of an immunoglobulin sequence, enabling a normalized reference to conserved positions in immunoglobulin families. Accordingly, the positions of any given immunoglobulin as defined by the EU index will not necessarily correspond to its sequential sequence. 
     General and specific scientific techniques are outlined in US Publications 2015/0307629, 2014/0288275 and WO2014/145806, all of which are expressly incorporated by reference in their entirety and particularly for the techniques outlined therein. 
     Example 1: Engineering IL-10 Fusion Proteins 
     As described above, cytokines such as IL-10 have short half-life, and high dose treatment is required to achieve a concentration of cytokines at the target (e.g. tumor site) sufficient to induce an immune response. However, based on observations with other cytokines, high dose treatment with IL-10 could potentially result in systemic toxicities. Further, the native IL-10 monomer is biologically inactive, and the biologically active IL-10 dimer becomes inactive upon disruption of the interactions between the two monomer units. In order to address these two caveats, we engineered various IL-10 formats as Fc fusion proteins (collectively referred to hereon as IL-10 fusion proteins or IL-10 fusions) with the aim both to promote a biologically active IL-10 and to enhance serum half-life through FcRn-mediated recycling. 
     1A: IL-10 Fusion Protein Formats 
     As described above, the biologically active IL-10 is a domain-swapped homodimer formed by non-covalent interactions between two IL-10 monomers. Each IL-10 monomer is composed of 6 helices, herein referred to as helices A-F. It has been previously reported that the non-covalent interaction that forms the biologically active IL-10 homodimer results from domain swapping between helices A-D (or “hIL-10(A-D)”; residues 1-116 of the mature form IL-10) of a first IL-10 monomer and helices E-F (or “hIL-10(E-F)”; residues 117-160 of the mature form IL-10) of a second IL-10 monomer. Here, we describe four categories of IL-10 fusion proteins engineered with the aim to either retain the dimeric nature of IL-10 or with the aim to circumvent the requirement for domain swapping between IL-10 monomers. 
     1A(a): IL10-Fc Fusions 
     Towards engineering an IL-10 fusion protein wherein the IL-10 homodimer is pre-complexed, a first IL-10 fusion category we conceived is the IL10-Fc fusion (cartoon schematics depicted in  FIG. 16 ). One such format of this category we engineered as a prototype is the (IL10) 2 -Fc format (cartoon schematic depicted in  FIG. 16A ) which comprises two identical monomers, each monomer comprising an IL-10 monomer covalently attached to the N-terminus of a homodimeric Fc chain. Illustrative proteins of the (IL10) 2 -Fc format include XENP24628, sequences for which are depicted in  FIG. 17 . Another format of this category we engineered as a prototype is the Fc-(IL10) 2  format (cartoon schematic depicted in  FIG. 16B ) which comprises two identical monomers, each monomer comprising an IL-10 monomer covalently attached to the C-terminus of a homodimeric Fc chain. Illustrative proteins of the Fc-(IL10) 2  format include XENP24632, sequences for which are depicted in  FIG. 18 . Yet another format of this category we engineered as a prototype is the (IL10-NC-IL10)-heteroFc format (cartoon schematic depicted in  FIG. 16C ) which comprises a first monomer comprising a first IL-10 monomer covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a domain linker) and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”, while a second IL-10 monomer is transfected separately so that a non-covalent IL-10 dimer is formed. Illustrative proteins of the (IL10-NC-IL10)-heteroFc format include XENP25955, sequences for which are depicted in  FIG. 19 . 
     1A(b): scIL10-Fc Fusion 
     Next, we sought to pre-complex the IL-10 homodimer as a single-chain IL-10 complex (or “scIL-10”) wherein a first IL-10 monomer is covalently attached to a second IL-10 monomer. We conceived a category of IL-10 fusions utilizing the scIL-10 hereon referred to as scIL10-Fc fusions (cartoon schematics depicted in  FIG. 20 ). One such format of this category we engineered as a prototype is the scIL10-heteroFc format (cartoon schematic depicted in  FIG. 20A ) which comprises a first monomer comprising a scIL-10 covalently attached to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative proteins of the scIL10-heteroFc format include XENP25880, sequences for which are depicted in  FIG. 21 . Another such format of this category we engineered as a prototype is the heteroFc-scIL10 format (cartoon schematic depicted in  FIG. 20B ) which comprises a first monomer comprising a scIL-10 covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a domain linker) and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative protein of the heteroFc-scIL10 is XENP28740, sequences for which are depicted in  FIG. 22 . 
     1A(c): IL10M1-Fc Fusion 
     Next, we explored IL-10 fusion formats engineered with the aim to circumvent the requirement for domain swapping between two IL-10 monomers. As discussed above, disruption of the non-covalent interaction which forms the biologically active IL-10 homodimer results in biologically inactive IL-10 monomers. However, Josephson et al. (2000) reported “IL-10M1” (or “IL10M1”; sequence depicted in  FIG. 15D ) which is a biologically active IL-10 monomer generated by engineering a Gly-Ser linker (GGGSGG (SEQ ID NO: 39)) between helices D and E of an IL-10 monomer. Josephson et al. reported that IL-10M1 is capable of binding IL-10R1 and recruiting IL-10R2 to induce IL-10 cellular responses. Accordingly, we conceived a category of IL-10 fusion proteins utilizing IL10M1 hereon referred to as IL10M1-Fc fusions (cartoon schematics depicted in  FIG. 23 ). One such format of this category we engineered as a prototype is the (IL10M1) 1 -heteroFc (cartoon schematic depicted in  FIG. 23E ) which comprises an IL10M1 covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative protein of the (IL10M1) 1 -heteroFc format is XENP14246, sequences for which are depicted in  FIG. 24 . Another such format of this category we engineered as a prototype is the heteroFc-(IL10M1) 1  (cartoon schematic depicted in  FIG. 23F ) which comprises an IL10M1 covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative protein of the heteroFc-(IL10M1) 1  format is XENP14247, sequences for which are depicted in  FIG. 25 . Yet another format of this category we engineered as a prototype is the (IL10M1) 2 -Fc format (cartoon schematic depicted in  FIG. 23A ) which comprises two identical monomers, wherein each monomer comprising an IL10M1 covalently attached to the N-terminus of a homodimeric Fc chain. An illustrative protein of the (IL10M1) 2 -Fc format is XENP25236, sequences for which are depicted in  FIG. 26 . A further format of this category we engineered as a prototype is the Fc-(IL10M1) 2  format (cartoon schematic depicted in  FIG. 23B ) which comprises two identical monomers, wherein each monomer comprising an IL10M1 covalently attached to the C-terminus of a homodimeric Fc chain. An illustrative protein of the Fc-(IL10M1) 2  format is XENP25237, sequences for which are depicted in  FIG. 27 . Yet a further format of this category we engineered as a prototype is the (IL10M1) 2 -heteroFc format (cartoon schematic depicted in  FIG. 23C ) which comprises a first monomer comprising a first IL10M1 covalently attached to a second IL10M1 (optionally via a linker) further covalently attached to the N-terminus of a first heterodimeric Fc chain (optionally via a linker), and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative protein of the (IL10M1) 2 -heteroFc format is XENP26887, sequences for which are depicted in  FIG. 28 . 
     1A(d): splitIL10-Fc Fusions 
     We reasoned that, instead of utilizing a Gly-Ser linker between IL10(A-D) and IL10(E-F) domains as in IL10M1, a biologically active IL-10 monomer could be generated by “splitting” the IL-10 monomer into its two domains (i.e. hIL-10(A-D) and hIL-10(E-F), sequences for which are depicted respectively in  FIGS. 15A-15B ), and that dimerization of the IL-10 domains would provide for a biologically active molecule referred to herein as a “splitIL10”. Accordingly, we conceived IL-10 fusions utilizing the splitIL10 hereon referred to as splitIL10-Fc fusions (cartoon schematics depicted in  FIG. 29 ). One such format of this category we engineered as a prototype is the splitIL10-heteroFc format (cartoon schematic depicted in  FIG. 29A ) which comprises a first monomer comprising hIL-10(A-D) covalently attached to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising hIL-10(E-F) covalently attached to the N-terminus of a complementary second heterodimeric Fc chain, so that dimerization of the heterodimeric Fc chains forces dimerization of the IL-10 domains. Illustrative proteins of the splitIL10-heteroFc format include XENP25242, sequences for which are depicted in  FIG. 30 . Another such format of this category we engineered as a prototype is the heteroFc-splitIL10 format (cartoon schematics depicted in  FIG. 29B ) which comprises a first monomer comprising a hIL-10(A-D) domain covalently attached to the C-terminus of a first heterodimeric Fc chain (optionally via a linker) and a second monomer comprising a hIL-10(E-F) domain covalently attached the C-terminus of a complementary second heterodimeric Fc chain (optionally via a linker). Illustrative proteins of the heteroFc-splitIL10 format include XENP25879, sequences for which are depicted in  FIG. 31 . 
     1B: Production of Prototype IL-10 Fusion Proteins 
     To produce XENP24628, an illustrative IL-10 fusion protein of the IL10-Fc category, plasmid coding for the IL-10 monomer was constructed by standard gene synthesis, followed by subcloning into a pTT5 expression vector containing an Fc fusion partner (e.g. homodimeric Fc chain as depicted in  FIG. 10 ). 
     To produce XENP25880, an illustrative IL-10 fusion protein of the scIL10-Fc category, plasmid coding for the scIL-10 complex was constructed by standard gene synthesis, followed by subcloning into a pTT5 expression vector containing an Fc fusion partner (e.g. a first heterodimeric Fc chain as depicted in  FIG. 11 ). An additional pTT5 expression vector coding for an empty-Fc (e.g. a corresponding second heterodimeric Fc chain as depicted in  FIG. 11 ) was also used. 
     To produce XENP25236, an illustrative IL-10 fusion protein of the IL10M1-Fc category, plasmid coding for the IL10M1 was constructed by standard gene synthesis, followed by subcloning into a pTT5 expression vector containing an Fc fusion partner (e.g. homodimeric Fc chain as depicted in  FIG. 10 ). 
     To produce XENP25242, an illustrative IL-10 fusion protein of the splitIL10-Fc fusion category, plasmids coding for hIL-10(A-D) and hIL-10(E-F) were constructed by standard gene synthesis, followed by subcloning into pTT5 expression vectors containing Fc fusion partners (e.g. heterodimeric Fc backbones as depicted in  FIG. 11 ). 
     Proteins were produced by transient transfection in HEK293E cells and were purified by a two-step purification process comprising protein A chromatography (purification part 1) followed by ion exchange chromatography (purification part 2). 
     1B(a): Purification of IL-10 Fusion Proteins 
     To illustrate the purification of IL-10 fusion proteins as described above, we describe here the purification and characterization of XENP25880. XENP25880 was purified from HEK293E supernatant as described above.  FIG. 32A  depicts the chromatogram showing purification part 2 of XENP25880 (cation exchange chromatography following protein A chromatography). The chromatogram shows the isolation of two peaks (peak A and peak B), which were further characterized by analytical size-exclusion chromatography with multi-angle light scattering (aSEC-MALS) and analytical cation-exchange chromatography (aCIEX) for identity, purity and homogeneity as generally described below. 
     Peaks A and B isolated from purification part 2 for XENP25880 were analyzed using aSEC-MALS to deduce their component protein species. The analysis was performed on an Agilent 1200 high-performance liquid chromatography (HPLC) system. Samples were injected onto a Superdex™ 200 10/300 GL column (GE Healthcare Life Sciences) at 1.0 mL/min using 1×PBS, pH 7.4 as the mobile phase at 4° C. for 25 minutes with UV detection wavelength at 280 nM. MALS was performed on a miniDAWN® TREOS® with an Optilab® T-rEX Refractive Index Detector (Wyatt Technology, Santa Barbara, Cali.). Analysis was performed using Agilent OpenLab Chromatography Data System (CDS) ChemStation Edition AIC version C.01.07 and ASTRA version 6.1.7.15. Chromatograms depicting aSEC separation profiles for peaks A and B are depicted in  FIG. 32B  along with MW of component species as determined by MALS. The profiles show that peak B comprises a dominant species of ˜92 kD which is consistent with the calculated molecular weight of XENP25880 (based on amino acid sequence) of 89.8 kDa. 
     The peaks from purification part 2 were also analyzed using analytical CIEX to further assess the purity and homogeneity of peaks A and B. The analysis was performed on an Agilent 1200 high-performance liquid chromatography (HPLC) system. Samples were injected onto a Proteomix SCX-NP5 5 μM non-porous column (Sepax Technologies, Inc., Newark, Del.) at 1.0 mL/min using 0-40% NaCl gradient in 20 mM MES, pH 6.0 buffer with UV detection wavelength at 280 nM. Analysis was performed using Agilent OpenLAB CDS ChemStation Edition AIC version C.01.07. Chromatogram depicting aCIEX separation of peaks A and B are depicted in  FIG. 32C . Notably, the aCIEX separation show that in the peak B material, there are charge variants in addition to a dominant peak. This will be addressed later in Example 3D. 
     1C: Biological Activity of IL-10 Fusions Proteins 
     Next, we investigated whether prototype IL-10 fusion proteins in each of the categories described above were biologically active. Following cytokine binding to their receptors, Janus kinases (JAKs) associated with the cytokine receptors phosphorylate STAT proteins which then translocate into the nucleus to regulate further downstream processes. In particular, IL-10 binds to the IL-10 receptor complex and activates JAK1 and Tyk2 which phosphorylate STAT3. Accordingly, we used STAT3 phosphorylation as an indicator of biological activity of prototype IL-10 fusion proteins in the IL10-Fc format (XENP24628), scIL10-Fc format (XENP25880), IL10M1-Fc format (XENP25236), and splitIL10-Fc format (XENP25242). 
     Human PBMCs were stimulated using 100 ng/ml anti-CD3 antibody (OKT3; plate-bound) for 2 days to induce expression of IL-10 receptors. Following stimulation, T cells were harvested and treated with the IL-10 fusions for 15 minutes. Following treatment, PBMCs were stained with anti-CD4-BV605 (RPA-T4) and anti-CD8-Alexa700 (SK1) antibodies for 30-45 minutes at room temperature. Cells were washed and incubated with pre-chilled (−20° C.) 90% methanol for 20-60 minutes. After incubation with methanol, cells were washed again and stained with anti-CD45RA-PE (H1100), anti-CD25-BV421 (M-A251), anti-FoxP3-Alexa488 (259D), and anti-pSTAT3-Alexa647 (pY705) to mark various populations and STAT3 phosphorylation. PBMCs were analyzed by flow cytometry, and data depicting STAT3 phosphorylation on various lymphocyte populations are depicted in  FIG. 33 . Notably, the data show that prototype IL-10 fusion in the scIL10-Fc format (XENP25880) induced STAT3 phosphorylation on various lymphocyte populations (albeit less potently than recombinant IL-10), while IL-10 fusions in the IL10-Fc, IL10M1-Fc, and splitIL10-Fc formats showed only baseline levels of STAT3 phosphorylation. 
     1D: Alternative C-Terminal Fc Fusion Format 
     Next, we investigated whether the geometry and positioning of IL-10 in the fusion proteins of the invention impacted their activity. Accordingly, we generated IL-10 fusion proteins with IL-10 molecule(s) covalently attached to the C-terminus of the Fc region. 
     One such format of the scIL10-Fc fusion category we engineered as a prototype is the heteroFc-scIL10 format (cartoon schematic depicted in  FIG. 20B ) which comprises a first monomer comprising a scIL-10 covalently attached to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a complementary second heterodimeric Fc chain that is “Fc-only” or “empty-Fc”. An illustrative protein of the heteroFc-scIL10 format is XENP28741, sequences for which are depicted in  FIG. 22 . 
     Here, we compare the induction of STAT3 phosphorylation by XENP28741 and XENP25981 (a corresponding scIL10-heteroFc fusion as a comparator; sequences for which are depicted in  FIG. 21 ). XENP28741 and XENP25981 were produced and purified as generally described in Example 1B. 
     Fresh PBMCs were treated with the IL-10 fusions for 15 minutes. Following treatment, PBMCs were stained with anti-CD3-BUV395 (UCHT1), anti-CD4-BV605 (RPA-T4), anti-CD8-Alexa700 (SK1), and anti-CD14-BV510 (M5E2) antibodies for 30-45 minutes at room temperature. Cells were washed and incubated with pre-chilled (−20° C.) 90% methanol for 20-60 minutes. After incubation with methanol, cells were washed again and stained with anti-CD45RA-PE (HI100), anti-CD25-BV421 (M-A251), anti-FoxP3-Alexa488 (259D), and anti-pSTAT3-Alexa647 (pY705) to mark various populations and STAT3 phosphorylation. PBMCs were analyzed by flow cytometry, and data depicting STAT3 phosphorylation on various lymphocyte populations are depicted in  FIG. 34 . The data show that C-terminal Fc fusion XENP28741 demonstrates greater potency in induction of STAT3 phosphorylation than N-terminal Fc fusion XENP25981 indicating that position of IL-10 in the fusion proteins of the invention does impact on their biological activity. 
     Example 2: Attenuating the Potency of IL-10 Fusion Proteins 
     We reasoned that decreasing the affinity of IL-10 fusion proteins for IL10R1 (and by extension, decreasing their potency) would decrease antigen sink and extend the half-life of the IL-10 fusion proteins. Towards this, we designed IL-10 variants with the aim to reduce affinity and potency of the IL-10 fusion proteins of the invention and investigated them in the context of scIL10-Fc fusions. 
     2A: Engineering IL-10 Variants for Reduced Affinity and Potency 
     Using the crystal structure of human IL-10 complexed with IL-10R1 as reported by Josephson et al. (2001) [PDB code 1J7V] and modeling in Molecular Operating Environment (MOE; Chemical Computing Group, Montreal, Quebec, Canada) software, we identified the following as IL-10 residues in contact with IL-10R1: N21, D28, Q38, D41, D44, Q42, N45, E142, D144, and E151 (numbered according to human IL-10 mature form sequence, as depicted in  FIG. 1 ). 
     Based on the above, we designed a number of IL-10 variants with isosteric substitutions (reasoning that isosteric substitutions have less potential for immunogenicity) at the contact residues with the aim to reduce the potency of biologically functional IL-10. Illustrative substitutions include N21D, D28N, Q38E, D41N, Q42E, D44N, N45D, E142Q, D144N, and E151Q. In addition, it has been previously reported by Yoon et al. (2012) that viral IL-10 (an IL-10 homolog encoded by Epstein-Barr virus; sequence for which is depicted in  FIG. 4 ) had a much weaker affinity for IL-10R1 in comparison to human IL-10. We investigated substitutions described by Yoon et al. at M39, L43, and 187 for their corresponding viral IL-10 residues (i.e. M39T, L43V, and I87A) as controls. It is envisioned that the substitutions described here can be used alone or in combination in the context of IL-10 monomer, IL-10 domains (e.g. hIL-10(A-D) and hIL-10(E-F)), IL10M1, or scIL-10. Sequences for illustrative IL-10 monomer variants comprising substitutions as described above are depicted in  FIG. 35 . It should be noted that the substitution numberings for IL-10 monomer are based on the mature form IL-10 sequence. 
     2B: Affinity of Variant IL-10 for IL-10 Receptor 
     To investigate the effect of substitutions described in Example 2A on the affinity of IL-10 for IL10R1, we first engineered the substitutions in the context of IL-10M1. Sequences for illustrative IL10M1 variants are depicted in  FIG. 36 . It should be noted that the substitution numberings for IL-10M1 variants are based on the mature form IL-10 sequence. 
     Illustrative (IL10M1) 1 -heteroFc fusions proteins comprising selected IL10M1 variants (sequences for which are depicted in  FIG. 40 ) were produced and purified as generally described in Example 1B. Next, we investigated the affinity of the variant IL-10 fusions for human IL10R1 using Octet, a BioLayer Interferometry (BLI)-based method. Experimental steps for Octet generally including the following: Immobilization (capture of ligand to a biosensor); Association (dipping of ligand-coated biosensors into wells containing serial dilutions of the analyte); and Dissociation (returning of biosensors to well containing buffer) in order to determine the affinity of the test articles. A reference well containing buffer alone was also included in the method for background correction during data processing. In particular, AR2G biosensor was used to capture IL10R1-Fc and dipped into multiple concentrations of each IL10M1-Fc test article. Kinetic analyses were performed by global fitting of binding data with a 1:1 Langmuir binding model. The resulting dissociation constant (K D ), association rate (k a ), and dissociation rate (k d ) are depicted in  FIG. 38 . As some of the sensorgrams were biphasic (as noted in the Figure), the dissociation constant as depicted does not appropriately reflect the effect of affinity engineering on some of the variants; accordingly, the maximum response is also depicted. Taken together, the dissociation constant and/or response show that we engineered IL-10 variants with a range of affinities for IL-10R1. 
     2C: In Vitro Potency of Variant IL-10 in a STAT3 Phosphorylation Assay 
     Next, we engineered substitutions identified in Example 2A in the context of single-chain IL-10 complex. Sequences for illustrative scIL-10 variants are depicted in  FIG. 39 . It should also be noted that for scIL10 variants, substitutions in monomer 1 and monomer 2 do not have to be identical. For example, for scIL10 variant designated huIL10.65, the first monomer comprises a N45D variant, but does not comprise a corresponding N45D variant in the second monomer (i.e. does not comprise N205D). 
     Illustrative scIL10-heteroFc and heteroFc-scIL10 fusion proteins comprising selected scIL-10 variants (sequences for which are respectively depicted in  FIGS. 40-41 ) were produced and purified as generally described in Example 1B. Next, we investigated the in vitro activity of the variant IL-10 fusions in a STAT3 phosphorylation assay as described in Example 1D. The data depicted in  FIG. 42  show that the engineered IL-10 as described above provided for IL-10 fusions with a wide range of potencies in inducing STAT3 phosphorylation suggesting that the substitutions identified in Example 2A are suitable for modulating the affinity and potency of IL-10 in various contexts (i.e. both in various IL-10 configurations as well as various IL-10 fusion formats). 
     2D: Induction of IFNγ by IL-10 Fusion Proteins 
     As described above, IL-10 can be either immunostimulatory or immunoinhibitory depending on context. Consistent with an immunostimulatory role, IL-10 has been reported to potentiate cancer immunity through induction of IFNγ-mediated T cell cytotoxicity (Mumm et al. (2013)). Chan et al. (2015) reported that IL-10, in particular, potentiates IFNγ secretion by CD8 +  T cells, while suppressing IFNγ in bulk PBMC culture. Additionally, Chan et al. note that IL-10 does not directly induce IFNγ secretion, but rather primes CD8 +  T cell for IFNγ secretion upon the appropriate stimulus (e.g. ligation of TCR). Accordingly, we investigated the IFNγ secretion by isolated CD8 +  T cells primed with the above-described IL-10 fusion proteins and triggered by an agonistic anti-CD3 antibody. In addition, we investigated expression of CD25 (a T cell activation marker as in known in the art) on CD8 +  T cells and percentage of CD8 +  T cells expressing Ki67 (a protein strictly associated with cell proliferation as is known in the art). 
     For these studies, we used CD8 +  T cells purified from PBMC using EasySep™ Human CD8 +  T Cell Enrichment Kit (STEMCELL Technologies, Vancouver, Canada). CD8 +  T cells were first incubated for 3 days with 10 μg/mL of immobilized anti-CD3 antibody (OKT3) and 2 μg/mL of immobilized anti-CD28 antibody (28.2) to induce IL-10 receptor expression on the CD8 +  T cells. CD8 +  T cells were then primed for 3 days with the indicated test articles followed by 4-5 hours stimulation by 1 μg/mL soluble anti-CD3 antibody. Supernatant was harvested and assessed for IFNγ secretion by the CD8 +  T cells using Human IFN-γ Tissue Culture Kit (Meso Scale Discovery, Rockville, Md.). Cells were then stained with anti-CD8-PE (RPA-T8) and anti-CD25-BV421 (M-A251) on ice for 45-60 minutes. Cells were washed and stained with anti-Ki67-APC using eBioscience™ Foxp3/Transcription Factor Staining Buffer Set (ThermoFisher Scientific) and assessed by flow cytometry. 
     The data as depicted in  FIGS. 43-44  show that the IL-10 fusion proteins do potentiate IFNγ secretion by CD8 +  T cells, activate CD8 +  T cells (as indicated by CD25 expression), and induces proliferation of CD8 +  T cells (as indicated by percentage cells expressing Ki67). Consistent with Examples 2B-2C showing a range of binding affinities and potencies in induction of STAT3 phosphorylation, fusions with affinity-engineered scIL-10 variants demonstrated a range of potencies in potentiation of IFNγ secretion, proliferation, and activation of CD8 +  T cells. Notably, as depicted in  FIGS. 45A-C , the EC50 for induction of STAT3 phosphorylation by the test articles correlated well with the EC50 for potentiation of IFNγ secretion, activation of CD8 +  T cells, and induction of CD8 +  T cell proliferation. 
     Example 3: Engineering the scIL10-Fc Format to Optimize Production 
     Here we describe engineering efforts to improve production of IL-10 fusions in the scIL10-Fc format. 
     3A: Swapping the scIL-10 from One Fc Chain to the Other 
     As depicted in  FIG. 32A , the separation between peaks A and B were suboptimal. We reasoned that this was due to the isoelectric points of each species (heterodimer vs. homodimer) and that swapping the scIL-10 complex from one arm of the heterodimeric Fc region (having a higher pI) to the other arm of the heterodimeric Fc region (having a lower pI) would provide for a greater difference in isoelectric points between the heterodimeric scIL10-heteroFc species and the homodimeric (scIL10) 2 -Fc and empty-Fc species. Accordingly, we investigated the production and purification of XENP25238 (sequences depicted in  FIG. 21 ), an IL-10 fusion in the scIL10-heteroFc fusion having the scIL-10 complex covalently attached to the heterodimeric Fc chain having a lower pI. XENP25238 was produced and purified as generally described in Example 1B.  FIG. 46A  depicts the chromatogram showing purification part 2 of XENP25238 showing the isolation of two peaks (peak B and peak BC), which were further characterized by aSEC-MALS and aCIEX for identity, purity and homogeneity as generally described in Example 1B(a) and depicted in  FIGS. 46B-C . The analysis show that peak B comprises a dominant species of ˜88 kD. Notably, as indicated by purification part 2, peak B comprising the scIL10-heteroFc fusion XENP25238 was dominant over peak BC comprising the empty-Fc (pI(+): pI(+)) homodimer. This represents an improvement over XENP25880 wherein purification part 2 (as depicted in  FIG. 32A ) resulted in a peak A comprising the empty-Fc (pI(−):pI(−)) homodimer that was dominant over peak B comprising the scIL10-heteroFc fusion XENP25880. As with XENP25880, the aCIEX separation show that in the peak B material comprising XENP25238, there are charge variants in addition to a dominant peak. 
     Experiment assessing STAT3 phosphorylation was performed as described in Example 1C to ascertain the biological activity of XENP25880. Data as depicted in  FIG. 47  show that swapping the scIL-10 complex from one chain of a heterodimeric Fc region to the other chain did not have an impact on activity. 
     3B: Engineering Linkers within the scIL-10 Construct 
     As another approach to improve the production of scIL10-Fc fusion proteins of the invention, we investigated engineering domain linkers of varying lengths between the first IL-10 monomer and the second IL-10 monomer within the scIL-10 complex.  FIG. 48  depicts sequences for illustrative scIL-10 complexes comprising domain linkers, and  FIG. 49  depicts sequences for illustrative scIL10-Fc fusion proteins comprising the scIL-10 complexes which were produced and purified as generally described in Example 1B. 
     Engineering linkers within the scIL-10 complex did not appear to substantially impact on the production of IL-10 fusions in the scIL10-heteroFc format (data not shown); however, activity was also unaffected as depicted in  FIG. 50  showing induction of STAT3 phosphorylation by scIL10-heteroFc fusions with varying linker lengths (experiment performed as described in Example 2C). 
     3C: Improved Yield Conveyed by N45D (and N205D) Substitution 
     Although the N45D substitution was introduced with the aim to reduce the affinity of IL-10 for the IL-10 receptor, the data depicted in Example 2C show that scIL10-heteroFc XENP25981 containing N45D and N205D exhibited activity similar to WT scIL10-heteroFc XENP25880. However, we surprisingly found that the N45D substitution improved the yield of the scIL10-heteroFc heterodimer. 
       FIG. 52  depicts the yield from expression of XENP25880 and XENP25981. The Figure lists total yield (mg/L) depicting yield of Fc-containing proteins as purified by protein A; percentage homodimer and heterodimer (as determined by aCIEX separation of the Protein A purified Fc-containing proteins; illustrative chromatograms depicted in  FIG. 51 ); and homodimer and heterodimer yields (mg/L) as calculated based on total yield and percentage homodimer/heterodimer. While there were some batch-to-batch variations in yield, the data show that production of XENP25981 generally resulted in greater yield of the scIL10-heteroFc fusion over the empty-Fc homodimer. 
     To investigate whether it was the N45D (and N205D) modification which conveyed the improved heterodimer yield, we engineered the N45D (and N205D) modification into the background of other variants (e.g. XENP25986 and XENP25993, sequences for which are depicted in  FIG. 53 ). As above, the yield from expression of XENP25880, XENP25981, XENP25986, and XENP25993 are depicted in  FIG. 54 . The data show that engineering the N45D in addition to Q38E (in XENP25986) or Q42E (in XENP25993) enhanced heterodimer expression relative to WT scIL10-heteroFc XENP25880. 
     3D: Removing Charge Variants 
     As shown in Examples 1B(a) and 3A, purified samples of molecules in the scIL10-heteroFc format such as XENP25880 and XENP25238 contained charge variants in addition to a dominant peak. We reasoned that this charge heterogeneity resulted from degradation-related post-translational modifications (PTMs) such as deamidation which contributes negative charge. While deamidation is normally slow and takes place following long term stress (e.g. during storage), we hypothesized that engineering the biologically functional IL-10 homodimer as a single-chain IL-10 complex and/or as a Fc fusion perturbed the IL-10 structure so that particular asparagine residues (such as those at the IL-10:IL-10 covalent attachment interface in the scIL-10 complex; or at the IL-10: Fc covalent attachment interface) were more susceptible to deamidation. Accordingly, we engineered IL-10 (and scIL-10) variants comprising substitution of select asparagine residues for alanine or glutamine (which although susceptible to deamidation, is much less so than asparagine). 
     In particular, it has previously been noted that asparagine preceding small residues such as glycine, serine, or alanine are most susceptible to deamidation (Stephenson et al. (1989)). Accordingly, we engineered modifications at residues N10, N92, N126, and N160 (as well as corresponding residues N170, N252, N286, and N320 in the scIL-10 complex). Illustrative IL-10 monomer variants include one or more of the following substitutions: N10A, N10Q, N92A, N126A, N160A. Illustrative scIL-10 variants include one or more of the following substitutions: N10A, N92A, N126A, N160A, N170A, N170Q, N252A, N286A, N320A, K317, I318, R319, and N320_. Sequences for illustrative IL-10 monomer variants and corresponding scIL-10 variants are depicted respectively in  FIGS. 55 and 56 . It should be noted that the substitution numberings for IL-10 variants are based on the mature form IL-10 sequence, and the substitution numberings for scIL10 variants are based on the scIL-10 sequences as depicted in  FIG. 15 . It should also be noted that for scIL-10 variants, the substitutions in monomer 1 and monomer 2 do not have to be identical. For example for scIL10 variant designated as huIL10.90, the first monomer does not comprise a modification at N160, while the second monomer comprises a modification at the corresponding residue (i.e. N320A). 
     Alternatively, we reasoned that the domain linker ((G 4 S) 2  (SEQ ID NO: 32)) between the scIL-10 complex and the Fc chain provides an additional deamidation site (i.e. N-G motif). Accordingly, we engineered XENP28295 and XENP28904 (scIL10-heteroFc fusions without a domain linker) as well as XENP28905 (an additional scIL10-heteroFc fusion without a domain linker and additionally comprising an scIL-10 variant having N10A and N170A substitutions as described above), sequences for which are depicted in  FIG. 59 . 
     In addition to deamidation, aspartic acid isomerization could also contribute to heterogeneity. As is known to those skilled in the art, there are particular motifs which cause an aspartic acid residue to be more susceptible to isomerization (see for example, Sydow et al. (2014), herein incorporated by reference). We generated an illustrative IL-10 variant with a substitution of residue D28 for alanine (sequences for IL-10 monomer variant and corresponding scIL-10 variant are depicted in  FIGS. 57-58 ). 
     The scIL-10 variants were engineered as part of scIL10-heteroFc fusion proteins (sequences for which are depicted in  FIG. 59 ), as well as part of a heteroFc-scIL10 fusion (sequences for which are depicted in  FIG. 60 ), and produced and purified as generally described in Example 1B. Protein A purified samples of XENP28295, XENP28635, and XENP28641 were characterized by aCIEX as generally described in Example 1B(a), chromatograms for which are depicted in  FIG. 61 . In comparing the chromatogram depicted in  FIG. 61A  for XENP25981 with the chromatogram depicted in  FIG. 61B  for XENP28295, we note that the acidic peak disappears for fusions without a N-terminal linker, presumably due to the elimination of N320 deamidation. In comparing the chromatogram depicted in  FIG. 61A  for XENP25981 with the chromatogram depicted in  FIG. 61C  for XENP28295 and XENP28641, we note that the acidic peak disappears for fusions with scIL-10 variants comprising N160A and N320A, again presumably due to the elimination of N320 deamidation. Unexpectedly, as shown in  FIG. 61D  chromatogram for XENP28635, it appears that the N10A substitution (and corresponding N170A substitution) removes the leading acidic peak. 
     Importantly, the scIL-10 variants engineered to remove potential degradation sites did not impact on the activity of the IL-10 fusions as indicated by induction of STAT3 phosphorylation (experiment performed as described in Example 2B; data depicted in  FIG. 62 ) and potentiation of IFNγ secretion by CD8 +  T cell, CD8 +  T cell proliferation, and CD8 +  T cell activation (experiment performed as generally described in Example 2D; data depicted in  FIG. 63 ). 
     3E: Removing Potential N-Glycosylation Site 
     The IL-10 monomer includes a glycosylation motif (N-X-S) at residues 116-118 (according to the human IL-10 mature form sequence). While it has been reported that human IL-10 is not glycosylated at this site (Westerhof et al. (2012)), we designed IL-10 variants (and corresponding scIL-10 variants) with the aim to abrogate potential for errant glycosylation. Accordingly, we engineered modifications at the following residues: N116, K117, S118 (according to the human IL-10 mature form sequence), and corresponding N276, K277, and S278 in the scIL-10 complex. Illustrative IL-10 monomer variants include one or more of the following substitutions: N116D, N116Q, K117P, and S118A. Illustrative scIL-10 variants include one or more of the following substitutions: N116D, N116Q, K117P, S118A, N276D, N276Q, K227P, and S228A. Sequences for illustrative IL-10 monomer variants and scIL-10 variants designed with the aim to remove the potential N-glycosylation site are depicted in  FIGS. 63-63 . scIL-10 variants were engineered as part of scIL10-heteroFc fusion proteins (sequences for which are depicted in  FIG. 66 ) and produced and purified as generally described in Example 1B. 
     3F: Removing Disulfide Bridges 
     The IL-10 monomer comprises two sets of disulfide bridges (formed by C12: C108 and C62: C114) which stabilizes the assembly of helices A-D (Walter et al., 2014). We reasoned that disulfide bridges may needlessly complicate the production of the scIL10-Fc fusion proteins of the invention and, for example, increase heterogeneity. Accordingly, we engineered modifications to remove the disulfide bridge. Sequences for illustrative IL-10 monomer variants (and corresponding scIL-10 variants) with modifications introduced with the aim to abrogate disulfide bridge formation are depicted in  FIGS. 67-68 . scIL-10 variants were engineered as part of scIL10-heteroFc fusion proteins (sequences for which are depicted in  FIG. 69 ) and produced and purified as generally described in Example 1B. 
     3G: Removing C-Terminal Lysine or Glycine-Lysine 
     As another approach towards improving production/purification of the IL-10 fusion proteins of the invention, the IL-10 fusions proteins were engineered with the lysine (K) or glycine-lysine (GK) at the C-terminus of the Fc region removed. Sequences for illustrative IL-10 fusion proteins having the C-terminal K or GK removed are scattered throughout the figures with annotation G 446 del and/or K447del. 
     Example 4: Further Engineering the IL10M1-Fc Format 
     As described in Example 1C, the prototype (IL10M1) 2 -Fc fusion XENP25236 was biologically inactive in a pSTAT3 assay, despite activity of the IL10M1 molecule alone as described by Josephson et al. (2000). We reasoned that retaining the activity of IL10M1 in the context of fusion to an Fc region requires further engineering of the IL10M1 molecule. Here we describe design of IL10M1 variants with the aim to restore activity of fusions in the IL10M1-Fc category. It should be noted that amino acid numbering in the following subsections of Example 4 are according to human IL-10 mature form sequence (without IL10M1 linker included in the numbering). 
     4A: Engineering Disulfide Bridges in IL10M1 
     In one approach, we reasoned that in view of intramolecular domain swapping (i.e. helices A-D and helices E-F within the same IL10M1 molecule) rather than intermolecular domain swapping (i.e. between helices A-D and helices E-F of two separate IL-10 monomers), the disulfide bridges stabilizing helices A-D (Walter et al., 2014) are no longer necessary, and may in fact be detrimental to activity of the IL10M1-Fc fusions, for example, through misfolding. Accordingly, we designed IL10M1 variants comprising modifications at C12, C62, C108, and/or C114 to remove the disulfide bridges. Illustrative IL10M1 variants are depicted in  FIG. 68 , and illustrative IL10M1-Fc fusions comprising the variants are depicted in  FIG. 69 . 
     Alternatively, it may be that in view of intramolecular domain swapping (i.e. helices A-D and helices E-F within the same IL10M1 molecule) rather than intermolecular domain swapping (i.e. between helices A-D and helices E-F of two separate IL-10 monomers), additional stabilization of the interaction between helices A-D and helices E-F are required. Based on the crystal structure of IL10M1 as described by Josephson et al. (2000) (PDB code 1Y6K), we identified the following residues as suitable for substituting with cysteine residues: F37, Q38, D41, L47, L48, S51, D55, F56, A64, M68, and V76 in helices A-D; and S118, A120, V121, K138, A139, M140, S141, E142, and Y153. In particular, we conceived introducing disulfide bridges between the following residue pairs: F37C:M140C, Q38C:S141C, D41C:K138C, L47C:K138C, L48C: E142C, S51C: A120C, D55C: A120C, F56C: Y153C, A64C:S118C, M68C: V121C, and V76C: A139C to promote stabilization of the interaction between helices A-D and helices E-F. Illustrative IL10M1 variants with engineered disulfide bridges are depicted in  FIG. 70 , and illustrative IL10M1-Fc fusions comprising the variants are depicted in  FIG. 71 . 
     4B: Stability Variants 
     In line with the idea above to stabilize the IL10M1 molecule, we used modeling in MOE software to identify single substitutions in core residues which may contribute to increased stability. Core residues we identified to be suitable for substitutions include: L19, L23, L26, A29, F30, V33, F37, L47, L48, L52, F56, A64, L65, S66, M68, 169, F71, Y72, V76, M77, A80, E81, 187, V91, L94, G95, L98, L101, L105, L112, S118, V121, V124, F128, K138, A139, M140, S141, F143, F146, 1147, and 1150. Using the Residue Scanning module in MOE software, we performed in silico single point mutations at the above identified residue to predict their effect on stability of IL10M1 and its affinity for IL10R1, data for which are shown in  FIG. 72A -AQ. 
     In addition, we used Rosetta software suite (RosettaCommons) for further stability modeling. The IL-10 dimer structure was prepared according to Rosetta&#39;s relax protocols. Next, we ran a number of fixed backbone optimization protocols of 100 trajectories each to explore the effect of allowing hydrophobic residues versus all amino acid residues either as independent mutations or in combination both in the context of single starting structure as well as in an ensemble of structures. We also used a flexible backbone approach that iterates between design and backbone movement. We used only sites in the core of each chain as identified above. 
     For illustrative purposes, we designed IL10M1 variants and produced IL10M1, and corresponding IL10M1-Fc fusions, with mutations (i.e. L47Q, S118A, and A139Q) which were consistently predicted to improve stability between the different approaches described above, sequences for which are depicted respectively in  FIGS. 73-74 . 
     4C: Engineering Alternative Linkers for IL10M1 
     Next, we designed IL10M1 variants with different linkers. In one approach, we aimed to increase the rigidity of the linker by introducing proline residues, removing serine residues, or shortening the linker length. Sequences for illustrative IL10M1 variants designed with this approach in mind are depicted in  FIG. 75 . Alternatively, we aimed to increase the flexibility of the linker, for example, by extending the linker length. Sequence for an illustrative IL10M1 variant designed with this approach in mind are also depicted in  FIG. 75 . Sequences for IL10M1-Fc fusions with these illustrative IL10M1 variants are depicted in  FIG. 76 . 
     Example 5: IL-10 Fusions Having IL-10 Variants with 109H-Based Sequence 
     A majority of the IL-10 fusions described above, and their component IL-10 variants, were generated in the context of the IL-10(109L) sequence. We engineered illustrative IL-10 variants in the context of the IL-10(109H) sequence (sequences for which are depicted in  FIG. 77 ). Next, we engineered IL-10 fusions in the scIL10-heteroFc and the heteroFc-scIL10 formats with the IL-10(109H) variants, sequences for which are depicted in  FIGS. 78 and 79 , to determine whether the different IL-10 sequence contexts impact the activity of the IL-10 fusions. These IL-10 fusions were produced as generally described in Example 1B. 
     Activity of the IL-10 fusions having IL-10(109H) variants were determined in a pSTAT3 assay as generally described above, data for which are depicted in  FIG. 80-85 . The data show that the IL-10 fusions based on the IL-10(109H) maintained a range of potency on the various cell types. Surprisingly, the data show that each of the IL-10 fusions based on the IL-10(109H) sequence demonstrated less efficacy (i.e. maximum induction of STAT3 phosphorylation) on each of the cell types investigated in comparison to corresponding IL-10 fusions (e.g. same variants) based on the IL-10(109L) sequence. This indicates that the particular residue at position 109 of IL-10 may be important for modulating the activity of IL-10 fusions. 
     Example 6: Further Engineering of IL-10 Fusion Proteins to Increase Half-Life 
     To further increase the half-life, the IL-10 fusion proteins of the invention were further engineered with Xtend Fc (M428L/N434S substitutions). Sequences for illustrative IL-10 fusion proteins with Xtend are depicted in  FIG. 86 . 
     Example 7: Engineering Targeted IL-10 Fusion Proteins 
     As described above, we envisioned the selectively targeting IL-10 to TILs expressing checkpoint receptors such as PD-1, or selectively targeting IL-10 to CD8 +  T cells. Accordingly, we envisioned a number of targeted IL-10 formats, cartoon schematics for which are depicted in  FIGS. 87-90 . 
       FIG. 87  depicts illustrative formats for targeted IL-10 fusions based on the IL10-Fc category, herein referred to as the “targeted IL10-Fc” category. 
       FIG. 88  depicts illustrative formats for targeted IL-10 fusions based on the scIL10-Fc category, herein referred to as the “targeted scIL10-Fc” category. One such format of this category we engineered is the “anti-X×scIL10-heteroFc” format which comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising a scIL-10 covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker). 
       FIG. 89  depicts illustrative formats for targeted IL-10 fusions based on the IL10M1-Fc category, herein referred to as the “targeted IL10M1-Fc” category. One such format of this category we engineered is the “anti-X×(IL10M1) 1 -heteroFc” format which comprises a first monomer comprising an antigen-binding domain covalently linked to the N-terminus of a first heterodimeric Fc chain and a second monomer comprising an IL10M1 covalently attached to the N-terminus of a second heterodimeric Fc chain (optionally via a domain linker). Another such format of this category we engineered is the “mAb-(IL10M1) 2 ” which comprises two identical monomers, each monomer comprising an antigen-binding domain covalently linked to the N-terminus of a homodimeric Fc chain which is covalently linked via the C-terminus, optionally via a linker, to an IL10M1. 
       FIG. 90  depicts illustrative formats for targeted IL-10 fusions based on the splitIL10-Fc category, herein referred to as the “targeted splitIL10-Fc” category. 
     Example 8: CD8-Targeted IL-10 Fusion Proteins 
     As described above, IL-10 potentiates cancer immunity primarily through CD8 +  T cells. In fact as described by Chan et al. (2015), incubation of IL-10 with bulk PBMCs leads to suppression of IFNγ secretion, suggesting that the immunosuppressive effect of IL-10 is potentiated through non-CD8 +  cell types. In addition, a high CD8/CD4 T cell ratio in TILs is generally considered a good prognostic marker for tumor therapy. Accordingly, we reasoned it would be useful to engineer CD8-targeted IL-10 fusion proteins to enhance the immunostimulatory potential of IL-10 by selectively targeting CD8 +  T cells. 
     8A: Production of Prototype CD8-Targeted IL-10 Fusion Proteins 
     Illustrative anti-CD8 and anti-NKG2D variable regions that find use in the CD8-targeted IL-10 fusion proteins of the invention are depicted in  FIGS. 92 and 93 . 
     Plasmids coding for IL-10 components or the anti-CD8 or anti-NKG2D variable regions were constructed by standard gene synthesis, followed by subcloning into a pTT5 expression vector containing fusion partners (e.g., backbones and/or CH1/partial hinge as depicted in  FIGS. 10, 11 , and/or  12 ). Proteins were produced by transient transfection in HEK293E cells and were purified by a two-step purification process comprising protein A chromatography (GE Healthcare) and ion exchange chromatography. 
     Sequences for illustrative CD8-targeted IL-10 fusions in the “anti-X×(IL10M1) 1 -heteroFc” are depicted in  FIG. 94 . Sequences for illustrative CD8-targeted IL-10 fusions in the “mAb-(IL10M1) 2 ” format are depicted in  FIG. 95 . Sequences for illustrative CD8-targeted and NKG2D-targeted IL-10 fusions in the “anti-X×scIL10-heteroFc” format are depicted respectively in  FIGS. 96 and 98 . Sequences for illustrative CD8-targeted IL-fusions in the “anti-X×scIL10-heteroFc” format comprising IL-10 variants are depicted in  FIG. 97 . 
     8B: Biological Activity of CD8-Targeted IL-10 Fusion Proteins 
     We investigated induction of STAT3 phosphorylation by the prototype CD8-targeted IL-10 fusions on various lymphocyte populations in an experiment performed as generally described in Example 1D, data for which are depicted in  FIG. 99 . The data show that the CD8-targeted IL-10 fusion XENP25794 induced STAT3 phosphorylation on CD8 +  T cells much more potently than the non-targeted IL-10 fusion (XENP25880). Notably for the test article concentration range investigated, it appears that the CD8-targeted IL-10 fusion induced STAT3 phosphorylation on CD4 +  T cells less potently than XENP25880. In addition, the NKG2D-targeted IL-10 fusion (XENP25952) also showed a selectivity for CD8 +  T cells over CD4 +  T cells indicating that additional targets other than CD8 may be used to target IL-10 fusion proteins to CD8 +  T cells. 
     Example 9: PD-1-Targeted IL-10 Fusion Proteins 
     As described above, immune checkpoint proteins such as PD-1 are up-regulated in tumor-infiltrating lymphocytes. Accordingly, PD-1-targeted IL-10 fusion proteins were conceived to selectively target T cells in the tumor environment. 
     9A: Production of Prototype PD-1-Targeted IL-10 Fusion Proteins 
     Illustrative anti-PD-1 variable regions that find use in the PD-1-targeted IL-10 fusion proteins of the invention are depicted in  FIG. 100 . 
     Plasmids coding for IL-10 components or the anti-PD-1 variable regions were constructed by standard gene synthesis, followed by subcloning into a pTT5 expression vector containing fusion partners (e.g., backbones and/or CH1/partial hinge as depicted in  FIGS. 10 ,  11 , and/or  12 ). Proteins were produced by transient transfection in HEK293E cells and were purified by a two-step purification process comprising protein A chromatography (GE Healthcare) and ion exchange chromatography. 
     Sequences for illustrative PD-1-targeted IL-10 fusions in the “anti-X×scIL10-heteroFc” format are depicted in  FIG. 101 . Further, sequences for illustrative PD-1-targeted IL-10 fusions in the “anti-X×scIL10-heteroFc” format comprising IL-10 variants are depicted in  FIG. 102 . Sequences for PD-1-targeted IL-10 fusion proteins in the “anti-X×heteroFc-scIL10” format are depicted in  FIG. 103 . 
     9B: Non-Competing PD-1 Binding Domain 
     Additionally, as it would be useful to combine the targeted IL-10 fusion proteins of the invention with PD-1 blockade antibodies, or to administer targeted IL-10 fusion proteins of the invention subsequent to treatment with PD-1 blockade antibodies, it is important that the PD-1 targeting arm of the targeted IL-10 fusion protein does not bind the same or similar epitope as the PD-1 blockade antibody. PD-1 blockade antibodies contemplated herein include, but are not limited to, nivolumab and pembrolizumab. 
     Illustrative non-competing anti-PD-1 binding domains contemplated for use in the PD-1-targeted IL-10 fusion proteins of the invention are referred to as mAb A, mAb B, and mAb C (sequences for their humanized variable regions are depicted in  FIG. 104 , humanized using string content optimization (see, e.g., U.S. Pat. No. 7,657,380, issued Feb. 2, 2010)). 
     Tandem epitope binning was performed to demonstrate that the mAbs did not compete with nivolumab and pembrolizumab. Epitope binning was performed using the Octet HTX instrument. AMC (anti-mouse Fc) biosensors were first used to capture murine-Fc fusions of human PD-1, dipping into 100 nM of a first antibody (indicated on the left side of  FIG. 105 ) and then dipped into 100 nM of a second antibody (indicated on the top of  FIG. 105 ). BLI-responses were normalized against the BLI-response of dipping the biosensor into HBS-EP buffer followed by dipping into the anti-PD-1 antibody. If the antibody pair provided a normalized BLI-response less than 0.5, the pair was considered competing or partially competing and to be in the same epitope bin, i.e., recognizing very similar, or largely overlapping, epitopes. If the antibody pair provided a normalized BLI-response greater than 0.5, the pair was considered non-competing and to bin to different epitopes. Antibodies tested were a bivalent anti-PD-1 mAb based on nivolumab, in-house produced pembrolizumab, chimeric mAb A, chimeric mAb B, and chimeric mAb C. PD-L1-Fc was also included to investigate the blocking of PD-1:PD-L1 interaction by the antibodies. The binning shows that anti-PD-1 mAb A, mAb B, and mAb C do not compete with nivolumab or pembrolizumab. Additionally, mAb A does not appear to block the PD-1:PD-L1 interaction, while mAb B and mAb C are partial blockers of the PD-1:PD-L1 interaction. Sequences for illustrative PD-1-targeted IL-10 fusions utilizing a PD-1-targeting arm based on humanized mAb C are depicted in  FIG. 106 . 
     9C: Biological Activity of PD-1-Targeted IL-10 Fusion Proteins 
     We investigated induction of STAT3 phosphorylation by the prototype PD1-targeted IL-10 fusion on various lymphocyte populations in an experiment performed as generally described in Example 1C, data for which are depicted in  FIG. 107 . Note that for this experiment, PBMC was first activated using 100 ng/ml anti-CD3 antibody (OKT3; plate-bound) for 2 days to induce expression of PD-1 and mimic the tumor environment. The data show that the PD1-targeted IL-10 fusion induced STAT3 phosphorylation on the various T cell populations much more potently than the non-targeted IL-10 fusion (XENP25880). 
     We also investigated the potentiation of IFNγ secretion and proliferation of CD8 +  T cell populations by prototype PD-1-targeted IL-10 fusions. For these studies, we used CD8 +  T cells purified from PBMC using EasySep™ Human CD8 +  T Cell Enrichment Kit (STEMCELL Technologies, Vancouver, Canada). CD8 +  T cells were first incubated for 3 days with 10 μg/mL of immobilized anti-CD3 antibody (OKT3) and 2 μg/mL of immobilized anti-CD28 antibody (28.2) to induce IL-10 receptor expression on the CD8 +  T cells. CD8 +  T cells were then primed for 3 days with the indicated test articles followed by 6 hours stimulation by 1 μg/mL soluble anti-CD3 antibody. Supernatant was harvested and assessed for IFNγ secretion by the CD8 +  T cells using Human IFN-γ Tissue Culture Kit (Meso Scale Discovery, Rockville, Md.). Cells were then stained with anti-CD8-PE (RPA-T8) and anti-CD25-BV421 (M-A251) on ice for 45-60 minutes. Cells were washed and stained with anti-Ki67-APC using eBioscience™ Foxp3/Transcription Factor Staining Buffer Set (ThermoFisher Scientific) and assessed by flow cytometry. Data showing IFNγ secretion by the CD8 +  T cells, CD8 +  T cell proliferation, and CD8 +  T cell activation are depicted in  FIG. 108 . 
     9D: PD-1-Targeting Restores Potency of Reduced Potency IL-10-Fc Fusions on Induction of CD8+ T Cell Proliferation 
     Next, the impact of PD-1-targeting on reduced potency IL-10-Fc fusions was investigated. CD8 +  T cells were first incubated for 3 days with 10 μg/mL of immobilized anti-CD3 antibody (OKT3) and 2 μg/mL of immobilized anti-CD28 antibody (28.2) to induce IL-10 receptor expression on the CD8 +  T cells. CD8 +  T cells were then primed for 3 days with the indicated test articles followed by 6 hours stimulation by 1 μg/mL soluble anti-CD3 antibody. Cells were then stained with staining antibodies including anti-CD8-BV421 (SK1) on ice for 45-60 minutes. Next, cells were washed and stained with anti-Ki67-APC using eBioscience™ Foxp3/Transcription Factor Staining Buffer Set (ThermoFisher Scientific) and assessed by flow cytometry. Test articles investigated were XENP30007 (scIL10.104-Fc), XENP30008 (scIL10.105-Fc), XENP30010 (scIL10.107-Fc), XENP30520 (αPD-1(mAb C_H1_L1.1)×huIL10.104)), XENP30521 (αPD-1(mAb C_H1_L1.1)×huIL10.105)), and XENP30522 (αPD-1(mAb C_H1_L1.1)×huIL10.107)). 
     Data showing proliferation of CD8 +  T cells as indicated by percentage of CD8 +  T cells that were Ki67+ are depicted in  FIG. 109 . For each of the reduced potency IL-10-Fc fusions, potency on induction of CD8 +  T cell proliferation was restored by PD-1-targeting. It is presumed that the CD8 +  T cells targeted for proliferation are PD-1-expressing CD8 +  T cells similar to those that would be found in the tumor environment. 
     9E: Further Tuning the Potency of PD-1-Targeted IL-10-Fc Fusions 
     Next, the impact of different PD-1-targeting arms as well as format of the PD-1-targeted IL-10-Fc fusions was investigated in a STAT3 phosphorylation assay as generally described above. Test articles investigated utilized a PD-1-targeting arm based on mAb C_H1_L1.1, a PD-1-targeting arm based on 1C11, or a RSV-targeting arm based on Numax/motavizumab; a weaker IL-10 variant (IL10.105) or a stronger IL-10 variant (IL10.102); as well as N-terminal scIL-10 vs C-terminal scIL-10. 
     Data showing phosphorylation of STAT3 are depicted in  FIG. 110 . In each case, the PD-1-targeted IL-10-Fc fusions were more potent than the corresponding RSV-targeted IL-10-Fc fusion. In most but not all instances, the PD-1-targeting arm based on 1C11 enhanced potency to a greater extent than the PD-1-targeting arm based on mAb C_H1_L1.1. Notably, for the weaker potency IL-10-Fc fusion (having IL10.105), C-terminal attachment of the scIL-10 resulted in lower potency irrespective of the particular targeting arm; while for the stronger potency IL-10-Fc fusion (having IL10.102), C-terminal attachment of the scIL-10 resulted in greater potency irrespective of the particular targeting arm. 
     Example 10: TIGIT-Targeted IL-10 Fusions Proteins 
     As described above, immune checkpoint proteins such as TIGIT are up-regulated in tumor-infiltrating lymphocytes. Accordingly, TIGIT-targeted IL-10 fusion proteins were conceived to selectively target T cells in the tumor environment. 
     10A: Generating TIGIT Binding Domain 
     Recombinant human TIGIT and cynomolgus TIGIT (sequences depicted in  FIG. 111 ) were used for phage panning. In-house de novo phage libraries were built displaying Fab and scFv variants (respectively referred to hereon as “Fab library” and “scFv library”) on phage coat protein pIII. Both the Fab library and the scFv library were panned in five rounds as follows: 1) human TIGIT, 2) cynomolgus TIGIT, 3) human TIGIT, 4) cynomolgus TIGIT, and 5) human TIGIT with increasing levels of stringency (both in terms of antigen concentration as well as wash stringency). after each round, eluted phage were added to log-phase XL1-Blue cells (Agilent, Wilmington, Del.) and amplified overnight at 37° C., 250 rpm. 
     192 clones were sequenced from each of the panning rounds 3, 4, and 5 from both the Fab library and the scFv library resulting in 1,152 clones. We investigated cell-surface binding of these clones on TIGIT-transfected Jurkat cells (hereon, Jurkat-TIGIT). 100K Jurkat-TIGIT cells were used per well on a 384-well plate, incubated with phage supernatant or control anti-TIGIT-APC (Biolegend, San Diego, Calif.) for 1 hour at 4° C. and washed. Cells were then stained with secondary antibodies and analyzed for phage binding by iQue Screener (Intellicyt, Albuquerque, N. Mex.).  FIGS. 115-116  depict an illustrative plate readout and associated histogram (380 clones+4 controls) with controls (control anti-TIGIT mAb, parental K07 phage+staining antibodies, staining antibodies only, and cell only), and our favorite clone (i.e. 2A5B4; sequences for which are depicted in  FIG. 112  as a bivalent mAb) highlighted. Based on analysis of both MFI and histograms indicating binding of phage clones to Jurkat-TIGIT cells, 92 unique clones were selected out of 1,152 clones. 
     Plasmids containing the variable heavy and variable light domains of the 92 clones were constructed by Gibson assembly and subcloned into a pTT5 expression vector containing the coding sequence for the IgG1 constant regions (with E233P/L234V/L235A/G 236 del/S67K ablation variants). DNA was transfected in HEK293E for expression and resulting bivalent mAbs were purified from the supernatant using protein A chromatography. 
     Next, we investigated the binding of the 92 bivalent mAbs to Jurkat-TIGIT. Jurkat-TIGIT cells were incubated with indicated concentrations of XENP27507 and phage-derived anti-TIGIT mAbs, as well as control antibody XENP19351 (a bivalent anti-TIGIT mAbs based on 10A7 as described in WO 2015/009856 with E233P/L234V/L235A/G236del/S67K ablation variants; sequences for which are depicted in  FIG. 113 ) for 1 hour at 4° C. Cells were then stained with Alexa Fluor® 647 AffiniPure F(ab′) 2  Fragment Goat Anti-Human IgG, Fcγ fragment specific secondary antibody (Jackson ImmunoResearch, West Grove, Pa.) for 1 hour at 4° C. and analyzed by flow cytometry. Data illustrating binding for XENP27507 and 5 additional phage-derived mAbs are depicted in  FIG. 117 , and show that each of the phage-derived mAbs were able to bind to Jurkat-TIGIT cells. 
     Finally, we performed an affinity screen of the 92 bivalent mAbs to TIGIT using Octet, a BioLayer Interferometry (BLI)-based method. Experimental steps for Octet generally includes the following: Immobilization (capture of ligand to a biosensor); Association (dipping of ligand-coated biosensors into wells containing the analyte); and Dissociation (returning of biosensors to well containing buffer) in order to determine the affinity of test articles. A reference well containing buffer alone was also included in the method for background correction during data processing. In particular, HIS1K biosensors were used to capture His-tagged human TIGIT or His-tagged cynomolgus TIGIT and dipped into 100 nM of each bivalent mAb. Kinetic analyses were performed by global fitting of binding data with a 1:1 Langmuir binding model. The resulting apparent dissociation constant (K Dapp ), association rate (k a ), and dissociation rate (k d ) are depicted in  FIG. 118  for XENP27507, selected 5 phage-derived mAbs, and control mAb XENP19351. The clones were ranked based on K Dapp  (K D  apparent, due to avidity concerns) values for human and cynomolgus TIGIT. The data show that each of the phage-derived mAbs bound to both human and cynomolgus TIGIT with a range of apparent K D . 
     Based on the above experiments investigating cell-surface TIGIT binding and K Dapp , we identified ˜20 suitable TIGIT ABD (out of 1,152 initial sequences) with a good balance of cell-surface antigen binding and affinity. 
     10A(a): Characterization of TIGIT Blockade 
     Blockade of checkpoint receptor/ligand interaction is necessary for inhibition of T cell anergy. Accordingly, it may be useful for the TIGIT-targeting arm of the targeted IL-10 fusion proteins to be capable of blocking the binding of CD112 and PVR to TIGIT. 
     In a first experiment, we performed tandem epitope binning using Octet to investigate whether the phage-derived mAbs bound the same epitope as XENP19351 (a confirmed blocker of TIGIT ligand) or XENP19352 (a confirmed non-blocker of TIGIT ligand; sequences for which are depicted in  FIG. 114 ), with the reasoning that phage-derived mAbs which binned to the same epitope as XENP19351 are blockers of TIGIT/TIGIT ligand interactions. HIS1K biosensors were first dipped into XENP23423 followed by dipping into 100 nM of XENP19351 or XENP19352 and then dipping into 100 nM of the indicated test articles. BLI-responses were normalized against the BLI-response of dipping the biosensor into HBS-EP buffer followed by dipping into the antibodies. If the antibody pair provided a BLI-response less than 0.5, the pair was considered competing and to be in the same epitope bin, i.e., recognizing very similar, or largely overlapping, epitopes. If the antibody pair provided a normalized BLI-response greater than 0.5, the pair was considered non-competing and to bin to different epitopes. The normalized BLI-response for each of the antibody pairs are summarized in  FIG. 119 . The data show that each of the phage-derived mAbs binned to the same epitope as XENP19351 (as indicated by BLI-response below 0.5) and a different epitope than XENP19352 (as indicated by BLI-response greater than 0.5) suggesting that the phage-derived mAbs are blockers of TIGIT:TIGIT ligand interactions. 
     To confirm the above, we investigated the blocking of TIGIT binding to cell-surface CD112 and PVR in a cell-based assay. Indicated concentrations of phage-derived mAbs, positive control antibody XENP19351 (confirmed blocker of TIGIT:TIGIT ligand interactions), or negative control anti-RSV mAb XENP15074 were mixed with 1 μg/mL of a murine Fc fusion of human TIGIT (TIGIT-mFc) for 30 minutes at room temperature. CD112-transfected or PVR-transfected CHO cells were then added and incubated for 30 minutes at 4° C. Cells were washed and stained with anti-murine Fc-A647 antibody to detect TIGIT-mFc binding to CD112 or PVR on CHO cells, and analyzed by flow cytometry. Data depicting binding of TIGIT-mFc to CD112-transfected CHO cells or PVR-transfected CHO cells are respectively depicted in  FIGS. 120A-B , and confirm that the phage-derived mAbs (including mAb based on 2A5B4) were able to block binding of TIGIT to both PVR and CD112. In another experiment performed similarly, percent blockade of PVR and CD112 were investigated, data for which are depicted in  FIGS. 121A-B . 
     10B: Production of Prototype TIGIT-Targeted IL-10 Fusion Proteins 
     Anti-TIGIT variable regions as described above were used to construct the prototype TIGIT-targeted IL-10 fusion proteins described herein. Sequences for additional anti-TIGIT variable regions which may find use in the TIGIT-targeted IL-10 fusion proteins of the inventions are depicted in  FIG. 122 . 
     Plasmids coding for IL-10 components or the anti-TIGIT variable regions were constructed by standard gene synthesis, followed by subcloning into a pTT5 expression vector containing fusion partners (e.g., backbones and/or CH1/partial hinge as depicted in  FIGS. 10, 11 , and/or  12 ). Proteins were produced by transient transfection in HEK293E cells and were purified by a two-step purification process comprising protein A chromatography (GE Healthcare) and ion exchange chromatography. 
     Sequences for illustrative TIGIT-targeted IL-10 fusions in the “anti-X×scIL10-heteroFc” format are depicted in  FIG. 123 . 
     10C: TIGIT-Targeting Restores Potency of Reduced Potency IL-10-Fc Fusions on Induction of CD8+ T Cell Proliferation 
     Next, the impact of TIGIT-targeting on reduced potency IL-10-Fc fusions was investigated. CD8 +  T cells were first incubated for 3 days with 10 μg/mL of immobilized anti-CD3 antibody (OKT3) and 2 μg/mL of immobilized anti-CD28 antibody (28.2) to induce IL-10 receptor expression on the CD8 +  T cells. CD8 +  T cells were then primed for 3 days with the indicated test articles followed by 6 hours stimulation by 1 μg/mL soluble anti-CD3 antibody. Cells were then stained with staining antibodies including anti-CD8-BV421 (SK1) on ice for 45-60 minutes. Next, cells were washed and stained with anti-Ki67-APC using eBioscience™ Foxp3/Transcription Factor Staining Buffer Set (ThermoFisher Scientific) and assessed by flow cytometry. Test articles investigated were XENP30007 (scIL10.104-Fc), XENP30008 (scIL10.105-Fc), XENP30010 (scIL10.107-Fc), XENP30523 (αTIGIT(2A5B4)×huIL10.104)), XENP30524 (αTIGIT(2A5B4)×huIL10.105)), and XENP30525 (αTIGIT(2A5B4)×huIL10.107)). 
     Data showing proliferation of CD8 +  T cells as indicated by percentage of CD8 +  T cells that were Ki67+ are depicted in  FIG. 124 . For each of the reduced potency IL-10-Fc fusions, potency on induction of CD8 +  T cell proliferation was restored by TIGIT-targeting. It is presumed that the CD8 +  T cells targeted for proliferation are TIGIT-expressing CD8 +  T cells similar to those that would be found in the tumor environment. 
     The examples set forth above are provided to give those of ordinary skill in the art a complete disclosure and description of how to make and use the embodiments of the compositions, systems and methods of the invention, and are not intended to limit the scope of what the inventors regard as their invention. Modifications of the above-described modes for carrying out the invention that are obvious to persons of skill in the art are intended to be within the scope of the following claims. All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the invention pertains. All references cited in this disclosure are incorporated by reference to the same extent as if each reference had been incorporated by reference in its entirety individually. 
     All headings and section designations are used for clarity and reference purposes only and are not to be considered limiting in any way. For example, those of skill in the art will appreciate the usefulness of combining various aspects from different headings and sections as appropriate according to the spirit and scope of the invention described herein. 
     All references cited herein are hereby incorporated by reference herein in their entireties and for all purposes to the same extent as if each individual publication or patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. Many modifications and variations of this application can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments and examples described herein are offered by way of example only, and the application is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which the claims are entitled.