Tapasin-R immunoglobulin-like domain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin-like domain on Tapasin-R. Tapasin is a V-C1 (variable-constant) immunoglobulin superfamily molecule present in the endoplasmic reticulum (ER), where it links MHC class I molecules to the transporter associated with antigen processing (TAP). Tapasin-R is a tapasin-related protein that contains similar structural motifs to Tapasin, with some marked differences, especially in the V domain, transmembrane and cytoplasmic regions. The majority of Tapasin-R is located within the ER; however, there may be some expression of Tapasin-R at the cell surface. Tapasin-R lacks an obvious ER retention signal.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 304 PKVRLSLANEA---LLPTLICDIAGYYPLDVVVTWTREELGGSPAQVS--GASFSSLRQSVAGTYSISSSLTAEPGS--A 376
Cdd:cd05771    1 PRVRLSPKNLVkpdLPQTLSCHIAGYYPLDVDVEWLREEPGGSESQVSrdGVSLSSHRQSVDGTYSISSYLTLEPGTenR 80

                         90       100
                 ....*....|....*....|
gi 157739930 377 GATYTCQVTHISLEEPLGAS 396
Cdd:cd05771   81 GATYTCRVTHVSLEEPLSVS 100

Tapasin-R immunoglobulin-like domain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin-like domain on Tapasin-R. Tapasin is a V-C1 (variable-constant) immunoglobulin superfamily molecule present in the endoplasmic reticulum (ER), where it links MHC class I molecules to the transporter associated with antigen processing (TAP). Tapasin-R is a tapasin-related protein that contains similar structural motifs to Tapasin, with some marked differences, especially in the V domain, transmembrane and cytoplasmic regions. The majority of Tapasin-R is located within the ER; however, there may be some expression of Tapasin-R at the cell surface. Tapasin-R lacks an obvious ER retention signal.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 304 PKVRLSLANEA---LLPTLICDIAGYYPLDVVVTWTREELGGSPAQVS--GASFSSLRQSVAGTYSISSSLTAEPGS--A 376
Cdd:cd05771    1 PRVRLSPKNLVkpdLPQTLSCHIAGYYPLDVDVEWLREEPGGSESQVSrdGVSLSSHRQSVDGTYSISSYLTLEPGTenR 80

                         90       100
                 ....*....|....*....|
gi 157739930 377 GATYTCQVTHISLEEPLGAS 396
Cdd:cd05771   81 GATYTCRVTHVSLEEPLSVS 100

Immunoglobulin C1-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 157739930  317 PTLICDIAGYYPLDVVVTWTReelGGSPAQvSGASFSSLRQSVAGTYSISSSL--TAEPGSAGATYTCQVTHISL 389
Cdd:pfam07654  15 NTLTCLVTGFYPPDITVTWLK---NGQEVT-EGVKTTPPSPNSDWTYQLSSYLtvTPSDWESGDEYTCRVEHEGL 85

First immunoglobulin variable (IgV) domain of nectin-2, nectin-like protein 5, and similar domains; The members here are composed of the second immunoglobulin (Ig) domain of nectin-2 (also known as poliovirus receptor related protein 2 or Cluster of Differentiation 112 (CD112)), nectin-like protein 5 (CD155), and similar proteins. Nectins and Nectin-like molecules are a family of Ca(2+)-independent immunoglobulin-like transmembrane glycoproteins belonging to the class of adhesion receptors, consisting of nine members (nectins 1 through 4 and nectin-like proteins 1 through 5). 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. Nectin-2 and nectin-3 localize at Sertoli-spermatid junctions where they form heterophilic trans-interactions between the cells that are essential for the formation and maintenance of the junctions and for spermatid development. CD155 is the fifth member in the nectin-like molecule family, and functions as the receptor of poliovirus; therefore, CD155 is also referred to as Necl-5, or PVR. In contrast to all other family members, CD155 lacks self-adhesion capacity, yet it shares with nectins the feature to interact with other nectins. For instance, CD155 heterophilically trans-interacts with nectin-3, thereby contributing significantly to the establishment of adherens junctions between epithelial cells. This group belongs to the Constant 1 (C1)-set of IgSF domains, which has one beta-sheet that is formed by strands A-B-E-D and the other strands by G-F-C-C'.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 189 VEFQVMTQTQSLsflLGSSASLDCGF-SMAPGLDLISVEWrlQHKGRGQLVYSWTAGQGQAVRKGATLE--PAQLGMA-R 264
Cdd:cd20989    1 VRVQVPPEVRGF---LGGSVTLPCHLlPPNMVTHVSQVTW--QRHDEHGSVAVFHPKQGPSFPESERLSfvAARLGAElR 75

                         90       100
                 ....*....|....*....|...
gi 157739930 265 DASLTLPGLTIQDEGTYICQITT 287
Cdd:cd20989   76 NASLAMFGLRVEDEGNYTCEFAT 98

Tapasin-R immunoglobulin-like domain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin-like domain on Tapasin-R. Tapasin is a V-C1 (variable-constant) immunoglobulin superfamily molecule present in the endoplasmic reticulum (ER), where it links MHC class I molecules to the transporter associated with antigen processing (TAP). Tapasin-R is a tapasin-related protein that contains similar structural motifs to Tapasin, with some marked differences, especially in the V domain, transmembrane and cytoplasmic regions. The majority of Tapasin-R is located within the ER; however, there may be some expression of Tapasin-R at the cell surface. Tapasin-R lacks an obvious ER retention signal.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 304 PKVRLSLANEA---LLPTLICDIAGYYPLDVVVTWTREELGGSPAQVS--GASFSSLRQSVAGTYSISSSLTAEPGS--A 376
Cdd:cd05771    1 PRVRLSPKNLVkpdLPQTLSCHIAGYYPLDVDVEWLREEPGGSESQVSrdGVSLSSHRQSVDGTYSISSYLTLEPGTenR 80

                         90       100
                 ....*....|....*....|
gi 157739930 377 GATYTCQVTHISLEEPLGAS 396
Cdd:cd05771   81 GATYTCRVTHVSLEEPLSVS 100

Immunoglobulin C-Type;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 157739930   318 TLICDIAGYYPLDVVVTWTReelGGSPAQvSGASFSSLRQSVAGTYSISSSLT--AEPGSAGATYTCQVTHISLEEP 392
Cdd:smart00407   3 TLVCLVSGFYPPDITVTWLR---NGQEVT-EGVSTTDPLKNSDGTYFLSSYLTvpASTWESGDVYTCQVTHEGLKEP 75

Immunoglobulin C1-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 157739930  317 PTLICDIAGYYPLDVVVTWTReelGGSPAQvSGASFSSLRQSVAGTYSISSSL--TAEPGSAGATYTCQVTHISL 389
Cdd:pfam07654  15 NTLTCLVTGFYPPDITVTWLK---NGQEVT-EGVKTTPPSPNSDWTYQLSSYLtvTPSDWESGDEYTCRVEHEGL 85

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DM; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DM. Human HLA-DM plays a critical role in antigen presentation to CD4 T cells by catalyzing the exchange of peptides bound to MHC class II molecules. Type 1 diabetes is correlated with DM activation and it is also implicated in viral infections such as herpes simplex virus, celiac disease, multiple sclerosis, other autoimmune diseases, and leukemia. MHC class II molecules play a key role in the initiation of the antigen-specific immune reponse. These molecules have been shown to be expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice. The expression of these molecules has been shown to be induced in nonprofessional APCs such as keratinocyctes, and they are expressed on the surface of activated human T cells and on T cells from other species. The MHC II molecules present antigenic peptides to CD4(+) T-lymphocytes. These peptides derive mostly from proteolytic processing via the endocytic pathway, of antigens internalized by the APC. These peptides bind to the MHC class II molecules in the endosome before they are transported to the cell surface. MHC class II molecules are heterodimers, comprised of two similarly-sized membrane-spanning chains, alpha and beta. Each chain had two globular domains (N- and C-terminal), and a membrane-anchoring transmembrane segment. The two chains form a compact four-domain structure. The peptide-binding site is a cleft in the structure.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 157739930 319 LICDIAGYYPLDVVVTWTReelGGSP-AQVSGASFSSLRqsvAG--TYSISSSLTAEPgSAGATYTCQVTHISLEEPL 393
Cdd:cd21002   22 LACHVWGFYPADVTITWLK---NGDPvAPHSSAPKTAQP---NGdwTYQTQVTLAVTP-SPGDTYTCSVQHASLPEPL 92

CH3 domain (third constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, gamma, and delta chains, and CH4 domain (fourth constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, epsilon, and mu chains; member of the C1-set of I; The members here are composed of the third and fourth immunoglobulin constant domain (IgC) of alpha, delta, gamma and alpha, epsilon, and mu heavy chains, respectively. This domain is found on the Fc fragment. 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 is composed of a constant domain and a variable domain. There are five types of heavy chains: alpha, delta, epsilon, gamma, and mu, all consisting of a variable domain (VH) with three (alpha, delta and gamma) or four (epsilon and mu) constant domains (CH1 to CH4). Ig molecules are modular proteins, in which the variable and constant domains have clear, conserved sequence patterns.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 157739930 318 TLICDIAGYYPLDVVVTWTReelGGSPAQVSGASFSSLRQSVAGTYSISSSLT--AEPGSAGATYTCQVTHISL 389
Cdd:cd05768   20 TLTCLVKGFYPEDIFVSWLQ---NGEPLPSADYKTTAPVPESDGSFFVYSKLNvsTADWNSGDVFSCVVGHEAL 90

CH2 domain (second constant Ig domain of the heavy chain) in immunoglobulin E (IgE); member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the second constant domain of the heavy chain of immunoglobulin E (IgE). The basic structure of immunoglobulin (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 is composed of a constant domain and a variable domain. There are five types of heavy chains: alpha, delta, epsilon, gamma, and mu, all consisting of a variable domain (VH) with three (alpha, delta, and gamma) or four (epsilon and mu) constant domains (CH1 to CH4). The different classes of antibodies vary in their heavy chains; the IgE class has the epsilon type. This domain (Cepsilon2) of IgE is in place of the flexible hinge region found in IgG.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 319 LICDIAGYYPLDVVVTWTreeLGGSPAQVSGASFSSLRQSvAGTYSISS--SLTAEPGSAGATYTCQVTH 386
Cdd:cd05847   21 LLCLISGYTPSTIEVEWL---VDGQVATLSAASTAPQKEE-GGTFSTTSklNVTQEDWKSGKTYTCKVTH 86

First immunoglobulin variable (IgV) domain of nectin-2, nectin-like protein 5, and similar domains; The members here are composed of the second immunoglobulin (Ig) domain of nectin-2 (also known as poliovirus receptor related protein 2 or Cluster of Differentiation 112 (CD112)), nectin-like protein 5 (CD155), and similar proteins. Nectins and Nectin-like molecules are a family of Ca(2+)-independent immunoglobulin-like transmembrane glycoproteins belonging to the class of adhesion receptors, consisting of nine members (nectins 1 through 4 and nectin-like proteins 1 through 5). 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. Nectin-2 and nectin-3 localize at Sertoli-spermatid junctions where they form heterophilic trans-interactions between the cells that are essential for the formation and maintenance of the junctions and for spermatid development. CD155 is the fifth member in the nectin-like molecule family, and functions as the receptor of poliovirus; therefore, CD155 is also referred to as Necl-5, or PVR. In contrast to all other family members, CD155 lacks self-adhesion capacity, yet it shares with nectins the feature to interact with other nectins. For instance, CD155 heterophilically trans-interacts with nectin-3, thereby contributing significantly to the establishment of adherens junctions between epithelial cells. This group belongs to the Constant 1 (C1)-set of IgSF domains, which has one beta-sheet that is formed by strands A-B-E-D and the other strands by G-F-C-C'.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 189 VEFQVMTQTQSLsflLGSSASLDCGF-SMAPGLDLISVEWrlQHKGRGQLVYSWTAGQGQAVRKGATLE--PAQLGMA-R 264
Cdd:cd20989    1 VRVQVPPEVRGF---LGGSVTLPCHLlPPNMVTHVSQVTW--QRHDEHGSVAVFHPKQGPSFPESERLSfvAARLGAElR 75

                         90       100
                 ....*....|....*....|...
gi 157739930 265 DASLTLPGLTIQDEGTYICQITT 287
Cdd:cd20989   76 NASLAMFGLRVEDEGNYTCEFAT 98

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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 194 MTQT-QSLSFLLGSSASLDCGFSMAPGLDLISveWRLQHKGRG-QLVYSWTAGQGQAVRKGATLEPAQLGMARDASLTLP 271
Cdd:cd00099    1 VTQSpRSLSVQEGESVTLSCEVSSSFSSTYIY--WYRQKPGQGpEFLIYLSSSKGKTKGGVPGRFSGSRDGTSSFSLTIS 78

                         90
                 ....*....|....*..
gi 157739930 272 GLTIQDEGTYICQITTS 288
Cdd:cd00099   79 NLQPEDSGTYYCAVSES 95

Immunoglobulin variable (IgV) domain of B7-H6; The members here are composed of the immunoglobulin variable (IgV) domain of B7-H6 (also known as NCR3LG1). B7-H6 contains one IgV domain and one IgC domain (IgV-IgC) and belongs to the B7-family, which consists of structurally related cell-surface protein ligands which bind to receptors on lymphocytes that regulate immune responses. B7-H6 is a ligand of NKp30, which is a member of CD28 family and an activating receptor of natural killer (NK) cells. The expression of NKp30 has been found in most of NK cells, which is involved in the process of tumor cell killing and interaction with antigen presenting cells (APCs) such as dendritic cells. Studies showed that NK cells eliminate B7-H6-expressing tumor cells either directly via cytotoxicity or indirectly by cytokine secretion. For instance, chimeric NKp30-expressing T cells responded to B7-H6(+) tumor cells and those T cells produced IFN-gamma and killed B7-H6-expressing tumor cells in vivo. B7-H6 mRNA is not found in normal cells, while high expression of B7-H6 is found in certain type tumor cells, such as lymphoma, leukemia, ovarian cancer, brain tumors, breast cancers, and various sarcomas. Since B7-H6 can bind NKp30 to exert anti-tumor effects by NK cells, which are able to recognize the difference between cancer cells and normal cells, B7-H6 may serve as a promising target for cancer immunotherapy.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 157739930 238 VYSWTAGQGQAVRKGATLEPAQLGMArDASLTLPGLTIQDEGTYICQITTSLYRAQQIIQLNI 300
Cdd:cd20981   53 VFEFFGDHQKAFRPGAIVSPWRLKSG-DASLQLPGVQLEEAGEYRCEVVVTPLKAQGTVQLEV 114

Immunoglobulin Variable (IgV) domain of B7-H4; The members here are composed of the immunoglobulin variable (IgV) domain of B7-H4 (also known as B7-S1, B7x, or Vtcn1). B7-H4 is one of the B7 family of immune-regulatory ligands that act as negative regulators of T cell function; it contains one IgV domain and one IgC domain. The B7-family consists of structurally related cell-surface protein ligands, which bind to receptors on lymphocytes that regulate immune responses. The binding of B7-H4 to unidentified receptors results in the inhibition of TCR-mediated T cell proliferation, cell-cycle progression and IL-2 production. As a co-inhibitory molecule, B7-H4 is widely expressed in tumor tissues and its expression is significantly associated with poor prognosis in human cancers such as glioma, pancreatic cancer, oral squamous cell carcinoma, renal cell carcinoma, and lung cancer.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 197 TQSLSFLLGSSASLDCGFSMAPGLDLISVEWrlQHKGRGQLVYSWTAGQGQAVR-----KGATLEPAQLGMARDASLTLP 271
Cdd:cd20984    4 AKHLAGNIGEDGILSCTFTPDIKLSDIVIQW--LKEGDSGLVHEFKEGKDELSRqspmfRGRTSLFADQVHVGNASLRLK 81

                         90
                 ....*....|....*..
gi 157739930 272 GLTIQDEGTYICQITTS 288
Cdd:cd20984   82 NVQLTDAGTYLCIISNS 98

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DQ and I-A; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of human histocompatibility antigen (HLA) DQ and mouse I-A. Three genetically distinct isotypes of class II MHC molecules are found in humans (HLA-DR, HLA-DQ, and HLA-DP), and two in mice (I-E and I-A). I-A and I-E have the same basic features insofar as peptide loading and presentation, they differ in that each interacts with distinctly different sets of peptides, and in the incidence of deletion of their genes. A structural understanding of the similarities and differences between I-A and I-E may help with understanding their roles in peptide presentation and T cell activation. Mouse I-Ag7 has a genetic susceptibility to autoimmune diabetes due to its small, uncharged amino acid residue at position 57 of their beta chain which results in the absence of a salt bridge between beta 57 and Arg alpha 76, which is adjacent to the P9 pocket of the peptide-binding groove. Human HLA-DR, -DQ, and -DP are about 70% similar to each other. HLA-DQ (DQ) is a cell surface receptor protein found on antigen presenting cells. It is an alphabeta heterodimer of type MHC class II. The alpha and beta chains are encoded by two loci, HLA-DQA1 and HLA-DQB1, that are adjacent to each other on chromosome band 6p21.3. A person often produces two alpha-chain and two beta chain variants and thus 4 isoforms of DQ. HLA-DQ is involved in the autoimmune diseases celiac disease and diabetes mellitus type. DQ is one of several antigens involved in rejection of organ transplants. DQ2 is encoded by the HLA-DQB1*02 allele group. DQ6 is encoded by the HLA-DQB1*06 allele group. DQ2 beta-chains combine with alpha-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms. These isoforms, nicknamed DQ2.2 and DQ2.5, are also encoded by the DQA1*0201 and DQA1*0501 genes, respectively. DQ6 beta-chains combine with alpha-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms. For DQ6, however, cis-isoform pairing only occurs with DQ1 alpha-chains. There are many haplotypes of DQ6. Susceptibility to Leptospirosis infection was found associated with undifferentiated DQ6. DQ8 is determined by the antibody recognition of beta8 and this generally detects the gene product of DQB1*0302. DQ8 is commonly linked to autoimmune disease in the human population. DQ8 is the second most predominant isoform linked to celiac disease and the DQ most linked to Type 1 diabetes. DQ8 increases the risk for rheumatoid arthritis and is linked to the primary risk locus for RA, HLA-DR4. DR4 also plays an important role in Type 1 diabetes. DQ8 is a split antigen of the DQ3 broad antigen. MHC class II molecules play a key role in the initiation of the antigen-specific immune response. They are expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice, and induced in nonprofessional APCs, such as keratinocyctes; they are expressed on the surface of activated human T cells and on T cells from other species. MHC II molecules present antigenic peptides to CD4(+) T-lymphocytes; these peptides derive mostly from proteolytic processing via the endocytic pathway, of antigens internalized by the APC, and bind to the MHC class II molecules in the endosome before they are transported to the cell surface. MHC class II molecules are heterodimers, comprised of two similarly-sized membrane-spanning chains, alpha and beta. Each chain had two globular domains (N- and C-terminal), and a membrane-anchoring transmembrane segment. The two chains form a compact four-domain structure. The peptide-binding site is a cleft in the structure.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 301 QASPKVRLSLA-NEAL--LPTLICDIAGYYPLDVVVTWTREELggspAQVSGASFSSLRQSVAGTYSISSSLTAEPgSAG 377
Cdd:cd21001    1 RVEPTVTISPSrTEALnhHNLLVCSVTDFYPGQIKVRWFRNDQ----EETAGVVSTPLIRNGDWTFQILVMLEMTP-QRG 75

                         90
                 ....*....|....*.
gi 157739930 378 ATYTCQVTHISLEEPL 393
Cdd:cd21001   76 DVYTCHVEHPSLQSPI 91

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen H; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen H (HLA-H). HLA-H (also known as hereditary hemochromatosis protein; HFE) is a major histocompatibility complex (MHC) class I-like protein that is mutated in Hereditary Hemochromatosis. HFE is a protein of 343 amino acids that includes a signal peptide, an extracellular transferrin receptor-binding region (a1 and a2), an immunoglobulin-like domain (a3), a transmembrane region, and a short cytoplasmic tail. HFE binds beta-2-microglobulin to form a heterodimer expressed at the cell surface. It binds transferrin receptor (TFRC) in its extracellular alpha1-alpha2 domain. HFE plays an important part in the regulation of hepcidin expression in response to iron overload and the liver is important in the pathophysiology of HFE-associated hemochromatosis. Nine HFE splicing variants have been reported with transcripts lacking exon 2 or exon 3, or exons 2-3, 2-4, or 2-5. Diverse mutations involving HFE introns and exons discovered in persons with hemochromatosis or their family members cause or probably cause high iron phenotypes. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 301 QASPKVRLSLANEALLPTLICDIAGYYPLDVVVTWTREElggSPAQVSGASFSSLRQSVAGTYSISSSLTAEPGSAgATY 380
Cdd:cd21021    2 QVPPLVKVTHHVTSSVTTLRCRALNYYPQNITMKWLKDK---QPMDAKEFEPKDVLPNGDGTYQGWITLAVPPGEE-QRY 77

                         90
                 ....*....|...
gi 157739930 381 TCQVTHISLEEPL 393
Cdd:cd21021   78 TCQVEHPGLDQPL 90

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) G; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) G. HLA-G histocompatibility antigen (also known as human leukocyte antigen G ; HLA-G) is a protein that in humans is encoded by the HLA-G gene. HLA-G belongs to the HLA nonclassical class I heavy chain paralogs. This class I molecule is a heterodimer consisting of a heavy chain and light chain, beta-2-microglobulin. The heavy chain is anchored in the membrane. HLA-G may play a role in immune tolerance in pregnancy, being expressed in the placenta by extravillous trophoblast cells (EVT), while the classical MHC class I genes (HLA-A and HLA-B) are not. Immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class I and class II. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells. MHC class II molecules play a key role in the initiation of the antigen-specific immune repose. These molecules have been shown to be expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice. The expression of these molecules has been shown to be induced in nonprofessional APCs such as keratinocyctes, and they are expressed on the surface of activated human T cells and on T cells from other species. The MHC II molecules present antigenic peptides to CD4(+) T-lymphocytes. These peptides derive mostly from proteolytic processing via the endocytic pathway, of antigens internalized by the APC. These peptides bind to the MHC class II molecules in the endosome before they are transported to the cell surface. MHC class II molecules are heterodimers, comprised of two similarly-sized membrane-spanning chains, alpha and beta. Each chain had two globular domains (N- and C-terminal), and a membrane-anchoring transmembrane segment. The two chains form a compact four-domain structure. The peptide-binding site is a cleft in the structure.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 157739930 318 TLICDIAGYYPLDVVVTWTREelggSPAQVSGASFSSLRQSVAGTYSISSSLTAePGSAGATYTCQVTHISLEEPL 393
Cdd:cd21022   20 TLRCWALGFYPAEIILTWQRD----GEDQTQDVELVETRPAGDGTFQKWAAVVV-PSGEEQRYTCHVQHEGLPEPL 90

CH1 domain (first constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, delta, epsilon, gamma, and mu chains; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the first immunoglobulin constant-1 set domain of alpha, delta, epsilon, gamma, and mu heavy chains. This domain is found on the Fab antigen-binding fragment. 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 is composed of a constant domain and a variable domain. There are five types of heavy chains: alpha, delta, epsilon, gamma, and mu, all consisting of a variable domain (VH) with three (alpha, delta and gamma) or four (epsilon and mu) constant domains (CH1 to CH4). Ig molecules are modular proteins, in which the variable and constant domains have clear, conserved sequence patterns. This group belongs to the C1-set of IgSF domains, which are classical Ig-like domains resembling the antibody constant domain. C1-set domains are found almost exclusively in molecules involved in the immune system, such as in immunoglobulin light and heavy chains, in the major histocompatibility complex (MHC) class I and II complex molecules, and in various T-cell receptors.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 319 LICDIAGYYPLDVVVTWTREELGGSPAQVSGasFSSLRQSvAGTYSISSSLT--AEPGSAGATYTCQVTH 386
Cdd:cd04985   21 LGCLISDYFPESITVSWQKNTNSITSGFTRT--FPVVLRS-GGDYSCSSQLTvpLQEWNSGEVYKCQVQH 87

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) I-E; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) I-E. Three genetically distinct isotypes of class II MHC molecules are found in humans (HLA-DR, HLA-DQ, and HLA-DP), and two in mice (I-E and I-A). I-A and I-E molecules have the same basic features insofar as peptide loading and presentation, although each interacts with distinctly different sets of peptides. They also differ in that there is a relatively high incidence of deletion of the I-E gene in both inbred strains of mice as well as wild mice and the lack of the reverse situation i.e. the deletion of I-A genes. A detailed structural understanding of the similarities and differences between I-A and the paralogous I-E could help illuminate the respective roles these molecules play in peptide presentation and T cell activation. Mouse I-Ag7 has a genetic susceptibility to autoimmune diabetes due to its small, uncharged amino acid residue at position 57 of their beta chain which results in the absence of a salt bridge between beta 57 and Arg alpha 76, which is adjacent to the P9 pocket of the peptide-binding groove. MHC class II molecules play a key role in the initiation of the antigen-specific immune reponse. These molecules have been shown to be expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice. The expression of these molecules has been shown to be induced in nonprofessional APCs such as keratinocyctes, and they are expressed on the surface of activated human T cells and on T cells from other species. The MHC II molecules present antigenic peptides to CD4(+) T-lymphocytes. These peptides derive mostly from proteolytic processing via the endocytic pathway, of antigens internalized by the APC. These peptides bind to the MHC class II molecules in the endosome before they are transported to the cell surface. MHC class II molecules are heterodimers, comprised of two similarly-sized membrane-spanning chains, alpha and beta. Each chain had two globular domains (N- and C-terminal), and a membrane-anchoring transmembrane segment. The two chains form a compact four-domain structure. The peptide-binding site is a cleft in the structure.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 157739930 319 LICDIAGYYPLDVVVTWTREelggSPAQVSGASFSSLRQSVAGTYSISSSLTAEPGSaGATYTCQVTHISLEEPL 393
Cdd:cd20998   25 LVCSVSDFYPGNIEVRWFRN----GKEEKTGIVSTGLVRNGDWTFQTLVMLETVPQS-GEVYTCQVEHPSLTDPV 94

Immunoglobulin (Ig)-like domain of protein zero (P0) and similar proteins; The members here are composed of the immunoglobulin (Ig) domain of protein zero (P0), a myelin membrane adhesion molecule. P0 accounts for over 50% of the total protein in peripheral nervous system (PNS) myelin. P0 is a single-pass transmembrane glycoprotein with a highly basic intracellular domain and an extracellular Ig domain. The extracellular domain of P0 (P0-ED) is similar to the Ig variable domain, carrying one acceptor sequence for N-linked glycosylation. P0 plays a role in membrane adhesion in the spiral wraps of the myelin sheath. The intracellular domain is thought to mediate membrane apposition of the cytoplasmic faces and may, through electrostatic interactions, interact directly with lipid headgroups. It is thought that homophilic interactions of the P0 extracellular domain mediate membrane juxtaposition in the extracellular space of PNS myelin. This group also contains the Ig domain of sodium channel subunit beta-2 (SCN2B), and of epithelial V-like antigen 1 (EVA). EVA, also known as myelin protein zero-like 2, is an adhesion molecule, which may play a role in structural organization of the thymus and early lymphocyte development. SCN2B subunits play a role in determining sodium channel density and function in neurons,and in control of electrical excitability in the brain.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 205 GSSASLDCGF-SMAPGLDLISVEWRLQHKGRGQLVYSWTAGQGQAVrkgaTLEPAQLG---------MARDASLTLPGLT 274
Cdd:cd05715   14 GSDVRLTCTFtSCYTVGDAFSVTWTYQPEGGNTTESMFHYSKGKPY----ILKVGRFKdrvswagnpSKKDASIVISNLQ 89

                         90
                 ....*....|.
gi 157739930 275 IQDEGTYICQI 285
Cdd:cd05715   90 FSDNGTYTCDV 100

CH3 domain (third constant Ig domain of heavy chains) in immunoglobulin heavy alpha, epsilon, and mu chains, and CH2 domain (second constant Ig domain of the gheavy chain) in immunoglobulin heavy gamma chain; member of the C1-set of Ig superfamily (IgSF) ; The members here are composed of the third immunoglobulin constant domain (IgC) of the gamma heavy chains and the second immunoglobulin constant domain (IgC) of alpha, epsilon, and mu heavy chains. This domain is found on the Fc fragment. 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 is composed of a constant domain and a variable domain. There are five types of heavy chains: alpha, delta, epsilon, gamma, and mu, all consisting of a variable domain (VH) with three (alpha, delta and gamma) or four (epsilon and mu) constant domains (CH1 to CH4). Ig molecules are modular proteins, in which the variable and constant domains have clear, conserved sequence patterns.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 300 IQASPKvRLSLANEALLPTLICDIAGYYplDVVVTWTREElgGSPAQvsgASFSSLRQSVAGTYSISSSLTAEPGS--AG 377
Cdd:cd07696    6 IPPSPK-DLFLTKSAKVTCLVVDLTSIE--EVNVTWSRED--GNEVL---ASTTNPEKHYNATLSVVSTLTVCADDwdNG 77

                         90       100
                 ....*....|....*....|.
gi 157739930 378 ATYTCQVTHISLEEPLGASTQ 398
Cdd:cd07696   78 KTFKCKVTHPDLPSPIVKSIQ 98

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) F; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen alpha chain F (HLA-F). HLA-F, encoded by the HLA-F gene in humans, belongs to the non-classical HLA class I heavy chain paralogs. This class I molecule mainly exists as a heterodimer associated with the invariant light chain beta-2-microglobulin. HLA-F molecules can interact with both activating and inhibitory receptors on immune cells, such as NK cells, and can present a diverse panel of peptides. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 157739930 318 TLICDIAGYYPLDVVVTWTREelggSPAQVSGASFSSLRQSVAGTYSISSSLTAePGSAGATYTCQVTHISLEEPL 393
Cdd:cd21023   21 TLRCWALGFYPAEITLTWQRD----GEEQTQDTELVETRPAGDGTFQKWAAVVV-PPGEEQRYTCHVQHEGLPQPL 91

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of T10, T22, and similar proteins; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of the murine H-2T-encoded T10, T22, and similar proteins. T10 and T22 are highly related nonclassical major histocompatibility complex (MHC) class Ib proteins that bind to certain gammadelta T cell receptors (TCRs) in the absence of other components. Classical MHC class I (class Ia) molecules participate in immune responses by presenting peptide antigens to cytolytic alpha beta T cells. Many nonclassical MHC class I (class Ib) molecules have distinct antigen-binding capabilities, suggesting that they have evolved for specific tasks that are distinct from those of MHC class Ia. Members of the IgC family are components of immunoglobulin, T-cell receptors, CD1 cell surface glycoproteins, secretory glycoproteins A/C, and major histocompatibility complex (MHC) class I/II molecules. In immunoglobulins, each chain is composed of one variable domain (IgV) and one or more IgC domains. These names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. The IgV domain is responsible for antigen binding, and the IgC domain is involved in oligomerization and molecular interactions.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 157739930 318 TLICDIAGYYPLDVVVTWTR--EELggspaqVSGASFSSLRQSVAGTYSISSSLTAEPGSAgATYTCQVTHISLEEPL 393
Cdd:cd21016   21 TLRCWALGFYPADITLTWQKdgEEL------TQDMEFVETRPAGDGTFQKWAAVVVPLGKE-QSYTCHVYHEGLPEPL 91

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DP; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DP. HLA class II histocompatibility antigen, DP(W2) beta chain is a protein that in humans is encoded by the HLA-DPB1 gene. It plays a central role in the immune system by presenting peptides derived from extracellular proteins. MHC class II molecules are encoded by three different loci, HLA-DR, -DQ, and -DP, which are about 70% similar to each other. HLA-DP is an alphabeta heterodimer cell-surface receptor. Each DP subunit (alpha-subunit, beta-subunit) is composed of a alpha-helical N-terminal domain, an IgG-like beta sheet, a membrane spanning domain, and a cytoplasmic domain. The alpha-helical domain forms the sides of the peptide binding groove. The beta sheet regions form the base of the binding groove and the bulk of the molecule as well as the inter-subunit (non-covalent) binding region. Individuals carrying the MHCII allele, HLA-DP2, are at risk for chronic beryllium disease (CBD), a debilitating inflammatory lung condition caused by the reaction of CD4 T cells to inhaled beryllium. MHC class II molecules play a key role in the initiation of the antigen-specific immune reponse. These molecules have been shown to be expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice. The expression of these molecules has been shown to be induced in nonprofessional APCs such as keratinocyctes, and they are expressed on the surface of activated human T cells and on T cells from other species. The MHC II molecules present antigenic peptides to CD4(+) T-lymphocytes. These peptides derive mostly from proteolytic processing via the endocytic pathway, of antigens internalized by the APC. These peptides bind to the MHC class II molecules in the endosome before they are transported to the cell surface. MHC class II molecules are heterodimers, comprised of two similarly-sized membrane-spanning chains, alpha and beta. Each chain had two globular domains (N- and C-terminal), and a membrane-anchoring transmembrane segment. The two chains form a compact four-domain structure. The peptide-binding site is a cleft in the structure.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157739930 304 PKVRLSLANEALLP---TLICDIAGYYPLDVVVTWTREelggSPAQVSGASFSSLRQSVAGTYSISSSLTAEPgSAGATY 380
Cdd:cd21003    4 PKVNVSPSKKGPLQhhnLLVCHVTDFYPGNIQVRWFLN----GQEETAGVVSTNLIHNGDWTFQILVMLEMTP-QQGDVY 78

                         90
                 ....*....|...
gi 157739930 381 TCQVTHISLEEPL 393
Cdd:cd21003   79 TCQVEHPSLDSPV 91

Class I major histocompatibility complex (MHC) beta-2-microglobulin; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin-like domain in beta-2-microglobulin (beta2m). Beta2m is the non-covalently bound light chain of the human class I major histocompatibility complex (MHC-I). Beta2m is structured as a beta-sandwich domain composed of two facing beta-sheets (four stranded and three stranded), that is typical of the C-type immunoglobulin superfamily. This structure is stabilized by an intramolecular disulfide bridge connecting two Cys residues in the facing beta-sheets. In vivo, MHC-I continuously exposes beta2m on the cell surface, where it may be released to plasmatic fluids, transported to the kidneys, degraded, and finally excreted.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 157739930 318 TLICDIAGYYPLDVVVtwtREELGGSPaqVSGASFSSLRQSVAGTYSISSSLTAEPgSAGATYTCQVTHISLEEP 392
Cdd:cd05770   20 VLNCYVSGFHPPDIEI---RLLKNGVK--IEDVEQSDLSFSKDWTFYLLKYTEFTP-TKGDEYACRVRHNTLSEP 88

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) H2Db and H2Ld; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ia major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) H2Db and H2Ld. H-2Ld complexed with peptide QL9 (or p2Ca) and complexed with influenza virus peptide NP366-374 (ASNEN-METM), respectively are high-affinity alloantigens for the 2C T cell receptor (TCR). The a1-a2 super domains of H-2Ld, H-2Db, and H-2Kb closely superimpose. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 157739930 318 TLICDIAGYYPLDVVVTWtreELGGSPAqVSGASFSSLRQSVAGTYSISSSLTAePGSAGATYTCQVTHISLEEPL 393
Cdd:cd21018   21 TLRCWALGFYPADITLTW---QLNGEEL-TQDMELVETRPAGDGTFQKWASVVV-PLGKEQNYTCRVYHEGLPEPL 91

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-2; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of QA-2. Qa-2 is a nonclassical MHC Ib antigen, which has been implicated in both innate and adaptive immune responses, as well as embryonic development. Qa-2 has an unusual peptide binding specificity in that it requires two dominant C-terminal anchor residues and is capable of associating with a substantially more diverse array of peptide sequences than other nonclassical MHC. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 157739930 318 TLICDIAGYYPLDVVVTWtreELGGSPAqVSGASFSSLRQSVAGTYSISSSLTAePGSAGATYTCQVTHISLEEPL 393
Cdd:cd21014   20 TLRCWALGFYPADITLTW---QLNGEEL-TQDMELVETRPAGDGTFQKWASVVV-PLGKEQNYTCHVNHEGLPEPL 90

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of HLA-Cw3 and HLA-Cw4; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of HLA-Cw3 and HLA-Cw4. HLA-C belongs to the MHC class I heavy chain receptors. The C receptor is a heterodimer consisting of a HLA-C mature gene product and beta-2-microglobulin. The mature C chain is anchored in the membrane. MHC Class I molecules, like HLA-C, are expressed in nearly all cells, and present small peptides to the immune system which surveys for non-self peptides. HLA-C is a locus on chromosome 6, which encodes for a large number of HLA-C alleles that are Class-I MHC receptors. Class Ib histocompatibility leukocyte antigens (HLA)-Cw3 and (HLA)-Cw4 are ligands for the natural killer (NK) cell inhibitory receptors KIR2DL2 and KIR2DL1, respectively. HLA-Cw3 and related alleles (HLA-Cw1, -Cw7, and -Cw8) contain Ser77 and Asn80 and interact with KIR that are reactive with the GL183 antibody Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. HLA-Cw4 and related alleles (HLA-Cw2, -Cw5, and -Cw6) have Asn77 and Lys80 and are recognized by KIR reactive with the EB6 15 or HP-3E4 16 antibody. Members of the IgC family are components of immunoglobulin, T-cell receptors, CD1 cell surface glycoproteins, secretory glycoproteins A/C, and major histocompatibility complex (MHC) class I/II molecules. In immunoglobulins, each chain is composed of one variable domain (IgV) and one or more IgC domains. These names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. The IgV domain is responsible for antigen binding, and the IgC domain is involved in oligomerization and molecular interactions.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 157739930 318 TLICDIAGYYPLDVVVTWTREelggSPAQVSGASFSSLRQSVAGTYSISSSLTAePGSAGATYTCQVTHISLEEPL 393
Cdd:cd21025   21 TLRCWALGFYPAEITLTWQWD----GEDQTQDTELVETRPAGDGTFQKWAAVVV-PSGEEQRYTCHVQHEGLPEPL 91

H-2 class I histocompatibility complex TLA (thymus leukemia antigen); member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the major histocompatibility complex (MHC) H-2 class I histocompatibility complex TLA (thymus leukemia antigen). The murine MHC class I histocompatibility TLA (Thymus leukemia antigen), which is encoded in the T region by T3 and T18 genes, is expressed mainly by intestinal epithelial cells and thymocytes. The murine TLAs are class I, beta-2-microglobulin-associated glycoproteins. The TLA function is not defined by antigen presentation, but rather by its relatively high affinity binding to CD8-alpha-alpha compared with CD8-alpha-beta. The existence of a human homolog for murine TLA remains unresolved. This group is a member of the C1-set Ig domains, which have one beta sheet that is formed by strands A, B, E, and D and the other strands by G, F, C, and C'.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 157739930 318 TLICDIAGYYPLDVVVTWtreELGGSPAqVSGASFSSLRQSVAGTYSISSSLTAePGSAGATYTCQVTHISLEEPL 393
Cdd:cd21012   21 TLRCWALGFYPAHITLTW---QLNGEEL-IQDTELVETRPAGDGTFQKWAAVVV-PSGEEQKYTCHVYHEGLPEPL 91