Immunoglobulin (Ig) light chain, kappa type, variable (V) domain; The members here are composed of the immunoglobulin (Ig) light chain, kappa type, variable (V) domain. This group contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. There are two types of light chains: kappa and lambda, each composed of a constant domain (CL) and a variable domain (VL). There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determines the type of immunoglobulin formed: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which seem to be functionally identical, and can associate with any of the heavy chains.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C     2 IVLTQSPGTLSLSPGERATLSCRASQSVSSSYLAWYQQKPGQAPRLLIYGASSRATGIPDRFSGSGSGTDFTLTISRLEP 81
Cdd:cd04980   1 IVMTQSPASLSVSPGERVTISCKASQSISSNYLAWYQQKPGQAPKLLIYYASTLHSGVPSRFSGSGSGTDFTLTISSVEP 80

                        90       100
                ....*....|....*....|....*.
1102_971C    82 EDFAVYYCQQYGSSPWTFGQGTKVEI 107
Cdd:cd04980  81 EDAAVYYCQQGYTFPYTFGGGTKLEI 106

Immunoglobulin (Ig) light chain, kappa type, variable (V) domain; The members here are composed of the immunoglobulin (Ig) light chain, kappa type, variable (V) domain. This group contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. There are two types of light chains: kappa and lambda, each composed of a constant domain (CL) and a variable domain (VL). There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determines the type of immunoglobulin formed: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which seem to be functionally identical, and can associate with any of the heavy chains.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C     2 IVLTQSPGTLSLSPGERATLSCRASQSVSSSYLAWYQQKPGQAPRLLIYGASSRATGIPDRFSGSGSGTDFTLTISRLEP 81
Cdd:cd04980   1 IVMTQSPASLSVSPGERVTISCKASQSISSNYLAWYQQKPGQAPKLLIYYASTLHSGVPSRFSGSGSGTDFTLTISSVEP 80

                        90       100
                ....*....|....*....|....*.
1102_971C    82 EDFAVYYCQQYGSSPWTFGQGTKVEI 107
Cdd:cd04980  81 EDAAVYYCQQGYTFPYTFGGGTKLEI 106

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C       6 QSPGTLSLSPGERATLSCRASQSVSS--SYLAWYQQKPGQAPRLLIYGASSRAT--GIPDRFSGSG--SGTDFTLTISRL 79
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCTYSSSMSEasTSVYWYRQPPGKGPTFLIAYYSNGSEegVKKGRFSGRGdpSNGDGSLTIQNL 80

                          90       100
                  ....*....|....*....|....*...
1102_971C      80 EPEDFAVYYCQQYGSSPWTFGQGTKVEI 107
Cdd:pfam07686  81 TLSDSGTYTCAVIPSGEGVFGKGTRLTV 108

Immunoglobulin (Ig) light chain, kappa type, variable (V) domain; The members here are composed of the immunoglobulin (Ig) light chain, kappa type, variable (V) domain. This group contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. There are two types of light chains: kappa and lambda, each composed of a constant domain (CL) and a variable domain (VL). There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determines the type of immunoglobulin formed: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which seem to be functionally identical, and can associate with any of the heavy chains.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C     2 IVLTQSPGTLSLSPGERATLSCRASQSVSSSYLAWYQQKPGQAPRLLIYGASSRATGIPDRFSGSGSGTDFTLTISRLEP 81
Cdd:cd04980   1 IVMTQSPASLSVSPGERVTISCKASQSISSNYLAWYQQKPGQAPKLLIYYASTLHSGVPSRFSGSGSGTDFTLTISSVEP 80

                        90       100
                ....*....|....*....|....*.
1102_971C    82 EDFAVYYCQQYGSSPWTFGQGTKVEI 107
Cdd:cd04980  81 EDAAVYYCQQGYTFPYTFGGGTKLEI 106

Immunoglobulin variable domain (IgV); The members here are composed of the immunoglobulin variable domain (IgV). The IgV family contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology, and are components of immunoglobulin (Ig) and T cell receptors. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. In Ig, each chain is composed of one variable domain (IgV) and one or more constant domains (IgC); these names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. Within the variable domain, there are regions of even more variability called the hypervariable or complementarity-determining regions (CDRs) which are responsible for antigen binding. A predominant feature of most Ig domains is the disulfide bridge connecting 2 beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E and, D strands in one sheet and A', G, F, C, C', and C" strands in the other.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C     4 LTQSPGTLSLSPGERATLSCRASQSVSSSYLAWYQQKPGQAPRLLIYGASSRAT---GIPDRFSGSGSG-TDFTLTISRL 79
Cdd:cd00099   1 VTQSPRSLSVQEGESVTLSCEVSSSFSSTYIYWYRQKPGQGPEFLIYLSSSKGKtkgGVPGRFSGSRDGtSSFSLTISNL 80

                        90       100       110
                ....*....|....*....|....*....|.
1102_971C    80 EPEDFAVYYCQQYGSS---PWTFGQGTKVEI 107
Cdd:cd00099  81 QPEDSGTYYCAVSESGgtdKLTFGSGTRLTV 111

Immunoglobulin (Ig) variable (V) domain of T-cell receptor (TCR) beta chain; The members here are composed of the immunoglobulin (Ig) variable domain of the beta chain of alpha/beta T-cell antigen receptors (TCRs). TCRs mediate antigen recognition by T lymphocytes, and are composed of alpha and beta, or gamma and delta, polypeptide chains with variable (V) and constant (C) regions. This group includes the variable domain of the alpha chain of alpha/beta TCRs. Alpha/beta TCRs recognize antigen as peptide fragments presented by major histocompatibility complex (MHC) molecules. The variable domain of TCRs is responsible for antigen recognition, and is located at the N-terminus of the receptor. Gamma/delta TCRs recognize intact protein antigens directly without antigen processing and recognize MHC independently of the bound peptide. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C     4 LTQSPGTLSLSPGERATLSCraSQSVSSSYLAWYQQKPGQAPRLLIYGASSRAT---GIP-DRFSGSG-SGTDFTLTISR 78
Cdd:cd05899   1 VTQSPRYLIKRRGQSVTLRC--SQKSGHDNMYWYRQDPGKGLQLLFYSYGGGLNeegDLPgDRFSASRpSLTRSSLTIKS 78

                        90       100
                ....*....|....*....|....*....
1102_971C    79 LEPEDFAVYYC---QQYGSSPWTFGQGTK 104
Cdd:cd05899  79 AEPEDSAVYLCassLGGGADEAYFGPGTR 107

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C       6 QSPGTLSLSPGERATLSCRASQSVSS--SYLAWYQQKPGQAPRLLIYGASSRAT--GIPDRFSGSG--SGTDFTLTISRL 79
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCTYSSSMSEasTSVYWYRQPPGKGPTFLIAYYSNGSEegVKKGRFSGRGdpSNGDGSLTIQNL 80

                          90       100
                  ....*....|....*....|....*...
1102_971C      80 EPEDFAVYYCQQYGSSPWTFGQGTKVEI 107
Cdd:pfam07686  81 TLSDSGTYTCAVIPSGEGVFGKGTRLTV 108

Immunoglobulin (Ig) variable (V) domain of T-cell receptor (TCR) gamma chain; The members here are composed of the immunoglobulin (Ig) variable (V) domain of the gamma chain of gamma/delta T-cell receptors (TCRs). TCRs mediate antigen recognition by T lymphocytes, and are heterodimers consisting of alpha and beta chains or gamma and delta chains. Each chain contains a variable (V) and a constant (C) region. The majority of T cells contain alpha/beta TCRs, but a small subset contain gamma/delta TCRs. Alpha/beta TCRs recognize antigens as peptide fragments presented by major histocompatibility complex (MHC) molecules. Gamma/delta TCRs recognize intact protein antigens directly without antigen processing and recognize MHC independently of the bound peptide. Gamma/delta T cells can also be stimulated by non-peptide antigens such as small phosphate- or amine-containing compounds. The variable domain of gamma/delta TCRs is responsible for antigen recognition and is located at the N-terminus of the receptor. Members of this group contain the standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C     4 LTQSPGTLSLSPGERATLSCRAS-QSVSSSYLAWYQQKPGQAPRLLIYGASSRAT-----GIPDRFSGS--GSGTDFTLT 75
Cdd:cd04982   1 LEQPQLSITREESKSVTISCKVSgIDFSTTYIHWYRQKPGQALERLLYVSSTSAVrkdsgKTKNKFEARkdVGKSTSTLT 80

                        90       100       110
                ....*....|....*....|....*....|...
1102_971C    76 ISRLEPEDFAVYYCQ--QYGSSPWT--FGQGTK 104
Cdd:cd04982  81 ITNLEKEDSATYYCAywESGSGYYIkvFGSGTK 113

Immunoglobulin (Ig) variable (V) domain of Cluster of Differentiation (CD) 8 beta chain; The members here are composed of the immunoglobulin (Ig)-like domain in Cluster of Differentiation (CD) 8 beta. The CD8 glycoprotein plays an essential role in the control of T-cell selection, maturation, and the T-cell receptor (TCR)-mediated response to peptide antigen. CD8 is comprised of alpha and beta subunits and is expressed as either an alpha/alpha or alpha/beta dimer. Both dimeric isoforms can serve as a coreceptor for T cell activation and differentiation, however they have distinct physiological roles, different cellular distributions, unique binding partners, etc. Each CD8 subunit is comprised of an extracellular domain containing a V-type Ig-like domain, a single pass transmembrane portion, and a short intracellular domain. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C     4 LTQSPGTLSLSPGERATLSCRASQSVSSSYLAWYQQKPGQAPR----LLIYGASSR----ATGI-PDRFS--GSGSGTDF 72
Cdd:cd07700   1 LLQTPGSLLVQTNQTVKMSCEAKTSPKNTRIYWLRQRQAPSKDshfeFLASWDPSKgivyGEGVdQEKLIilSDSDSSRY 80

                        90       100       110
                ....*....|....*....|....*....|..
1102_971C    73 TLTISRLEPEDFAVYYCQQYGSSPWTFGQGTK 104
Cdd:cd07700  81 ILSLMSVKPEDSGTYFCMTVGSPELIFGTGTK 112

Immunoglobulin (Ig)-like variable (V) domain of the Signal-Regulatory Protein (SIRP); The members here are composed of the immunoglobulin (Ig)-like domain of the Signal-Regulatory Protein (SIRP). The SIRPs belong to the "paired receptors" class of membrane proteins that comprise several genes coding for proteins with similar extracellular regions, but very different transmembrane/cytoplasmic regions with different (activating or inhibitory) signaling potentials. They are commonly on NK cells, but are also on many myeloid cells. Their extracellular region contains three immunoglobulin superfamily domains, a single V-set, and two C1-set IgSF domains. Their cytoplasmic tails that contain either ITIMs or transmembrane regions have positively charged residues that allow an association with adaptor proteins, such as DAP12/KARAP, containing ITAMs. There are 3 distinct SIRP members: alpha, beta, and gamma. SIRP alpha (also known as CD172a or SRC homology 2 domain-containing protein tyrosine phosphatase substrate 1/Shps-1) is a membrane receptor that interacts with a ligand CD47 expressed on many cells and gives an inhibitory signal through immunoreceptor tyrosine-based inhibition motifs in the cytoplasmic region that interact with phosphatases SHP-1 and SHP-2. SIRP beta has a short cytoplasmic region and associates with a transmembrane adapter protein DAP12 containing immunoreceptor tyrosine-based activation motifs to give an activating signal. SIRP gamma contains a very short cytoplasmic region lacking obvious signaling motifs, but also binds CD47 with much less affinity. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C     4 LTQSPGTLSLSPGERATLSCRASQSVSSSYLAWYQqkpGQAP-RLLIY----GASSRATGIPDrfSGSGSGTDFTLTISR 78
Cdd:cd16097   2 VIQPEKSVSVAAGESATLHCTVTSLIPVGPIQWFR---GAGPgRELIYnqkeGHFPRVTTVSD--LTKRNNMDFSIRISN 76

                        90       100       110
                ....*....|....*....|....*....|....*
1102_971C    79 LEPEDFAVYYCQQY--GSSPWT---FGQGTKVEIK 108
Cdd:cd16097  77 ITPADAGTYYCVKFrkGSPDDVefkSGAGTELSVR 111

Immunoglobulin (Ig)-like domain of Programmed Cell Death 1 (PD1); The members here are composed of the immunoglobulin (Ig)-like domain of Programmed Cell Death 1 (PD1; also known as CD279/cluster of differentiation 279). PD1 is a cell surface receptor that is expressed on T cells and pro-B cells. The protein's structure includes an extracellular IgV domain followed by a transmembrane region and an intracellular tail. Activation of CD4+ T cells, CD8+ T cells, NKT cells, B cells, and monocytes induces PD-1 expression, immediately after which it binds two distinct ligands, PD-L1 (also known as B7-H1 or CD274/cluster of differentiation 274) and PD-L2, also known as B7-DC. PD-1 plays an important role in down regulating the immune system by preventing the activation of T-cells, reducing autoimmunity and promoting self-tolerance. The inhibitory effect of PD-1 is accomplished by promoting apoptosis in antigen specific T-cells in lymph nodes while simultaneously reducing apoptosis in regulatory T cells. A class of drugs that target PD-1, known as the PD-1 inhibitors, activate the immune system to attack tumors and treat cancer. Comparisons between the mouse PD-1 (mPD-1) and human PD-1 (hPD-1) reveals that unlike the mPD-1 which has a conventional IgSF V-set domain, hPD-1 lacks a C" strand, and instead the C' and D strands are connected by a long and flexible loop. In addition, the BC loop is not stabilized by disulfide bonding to the F strand of the ligand binding beta sheet. These differences result in different binding affinities of human and mouse PD-1 for their ligands.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C     4 LTQSPGTLSLSPGERATLSCRASQSVSSSYLAWYQQKPG-QAPRLLIYGASSRATGIPDRFSGSG--SGTDFTLTISRLE 80
Cdd:cd16088   2 PTFSPALLVVTEGANATFTCSFSNTSESFVLNWYRLSPSnQTDKLAAFPEDRSQPGQDWRFRVTQlpNGRDFHMSVVRAR 81

                ....*....
1102_971C    81 PEDFAVYYC 89
Cdd:cd16088  82 RNDSGTYLC 90

First immunoglobulin (Ig) domain of Cluster of Differentiation (CD) 4; member of the V-set of IgSF domains; The members here are composed of the first immunoglobulin (Ig) domain of Cluster of Differentiation (CD) 4. CD4 and CD8 are the two primary co-receptor proteins found on the surface of T cells, and the presence of either CD4 or CD8 determines the function of the T cell. CD4 is found on helper T cells, where it is required for the binding of MHC (major histocompatibility complex) class II molecules, while CD8 is found on cytotoxic T cells, where it is required for the binding of MHC class I molecules. CD4 contains four immunoglobulin domains, with the first three included in this hierarchy. The fourth domain has a general Ig architecture, but has slight topological changes in the arrangement of beta strands relative to the other structures in this family and is not specifically included in the hierarchy.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
1102_971C    16 GERATLSCRASQSVSSSYlAW---YQQKP-GQAPRLLIYGASSRATGIPDRFSGSGSGTdFTLTISRLEPEDFAVYYCQ 90
Cdd:cd07690   9 GDTAELPCTASQKKSIQF-HWknsNQIKIlGNQGSFLTKGPSKLNDRADSRRNLWDQGS-FPLIIKNLKIEDSDTYICE 85

Immunoglobulin variable domain (IgV) Cluster of Differentiation (CD) 79B; The members here are composed of the immunoglobulin variable domain (IgV) of the Cluster of Differentiation (CD) 79B (also known as CD79b molecule, immunoglobulin-associated beta (Ig-beta), and B29). The B lymphocyte antigen receptor is a multimeric complex that includes the antigen-specific component, surface immunoglobulin (Ig). Surface Ig non-covalently associates with two other proteins, Ig-alpha and Ig-beta, which are necessary for expression and function of the B-cell antigen receptor. This gene encodes the Ig-beta protein of the B-cell antigen component. Alternatively spliced transcript variants encoding different isoforms have been described. Members of the IgV family are components of immunoglobulin (Ig) and T cell receptors. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. In Ig, each chain is composed of one variable domain (IgV) and one or more constant domains (IgC); these names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. Within the variable domain, there are regions of even more variability called the hypervariable or complementarity-determining regions (CDRs) which are responsible for antigen binding. A predominant feature of most Ig domains is the disulfide bridge connecting 2 beta-sheets with a tryptophan residue packed against the disulfide bond. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|..
1102_971C    30 SSSYLAWYQQKPGQAPRLLIYGASsratgipdRFSGSGSGTDFTLTISRLEPEDFAVYYCQQ 91
Cdd:cd16096  24 YSGVMTWFRKKGNQRPQELFPEDG--------RISQTQNGSVYTLTIQNIQYEDNGIYFCQQ 77

First immunoglobulin variable (IgV) domain of nectin-1, and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of nectin-1 (also known as poliovirus receptor related protein 1 (PVRL1) or cluster of differentiation (CD) 111). Nectin-1 belongs to the nectin family comprised of four transmembrane glycoproteins (nectins-1 through -4). Nectins are synaptic cell adhesion molecules (CAMs) which facilitate adhesion and signaling at various intracellular junctions. Nectins form homophilic cis-dimers, followed by homophilic and heterophilic trans-dimers involved in cell-cell adhesion. In addition nectins heterophilically trans-interact with other CAMs such as nectin-like molecules (Necls), nectin-1 for example, has been shown to trans-interact with Necl-1. Nectins also interact with various other proteins, including the actin filament (F-actin)-binding protein, afadin. Mutation in the human nectin-1 gene is associated with cleft lip/palate ectodermal dysplasia syndrome (CLPED1). Nectin-1 is a major receptor for herpes simplex virus through interaction with the viral envelope glycoprotein D.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
1102_971C    16 GERATLSCR---ASQSVSSSYLAWYQQKPGQAPRLLIYGASSRATGIP---DRFS-GSGSGTDFTLTISRLEPEDFAVYY 88
Cdd:cd05886  14 GTDVVLHCSfanPLPSVKITQVTWQKSTNGSKQNVAIYNPSMGVSVLPpyrERVTfLNPSFTDGTIRLSRLELEDEGVYI 93

                ..
1102_971C    89 CQ 90
Cdd:cd05886  94 CE 95