immunoglobulin domain of neonatal Fc receptor, major histocompatibility complex (MHC)-like; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin domain of neonatal Fc receptor (FcRn). FcRn performs two distinct functions: the transport of maternal immunoglobulin G (IgG) to pre- or neonatal mammals which provides passive immunity and protection of IgG from normal serum protein catabolism. FcRn is related to class I MHC proteins, but lacks a functional peptide binding groove. 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 2462563745  58 EWKEPPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRNGLAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIV 137
Cdd:cd21011     1 EWKEPPSMRLKARPGSPGFSVLTCSAFSFYPPELQLRFLRNGLAAGSGEGDFGPNGDGSFHAWSSLTVKSGDEHHYRCVV 80

                          90
                  ....*....|...
gi 2462563745 138 QHAGLAQPLRVEL 150
Cdd:cd21011    81 QHAGLAQPLTVEL 93

immunoglobulin domain of neonatal Fc receptor, major histocompatibility complex (MHC)-like; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin domain of neonatal Fc receptor (FcRn). FcRn performs two distinct functions: the transport of maternal immunoglobulin G (IgG) to pre- or neonatal mammals which provides passive immunity and protection of IgG from normal serum protein catabolism. FcRn is related to class I MHC proteins, but lacks a functional peptide binding groove. 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 2462563745  58 EWKEPPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRNGLAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIV 137
Cdd:cd21011     1 EWKEPPSMRLKARPGSPGFSVLTCSAFSFYPPELQLRFLRNGLAAGSGEGDFGPNGDGSFHAWSSLTVKSGDEHHYRCVV 80

                          90
                  ....*....|...
gi 2462563745 138 QHAGLAQPLRVEL 150
Cdd:cd21011    81 QHAGLAQPLTVEL 93

Immunoglobulin C1-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 2462563745  78 VLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTV-----KSGDEhhYCCIVQHAGL 142
Cdd:pfam07654  16 TLTCLVTGFYPPDITVTWLKNGqeVTEGVKTTPPSPNSDWTYQLSSYLTVtpsdwESGDE--YTCRVEHEGL 85

immunoglobulin domain of neonatal Fc receptor, major histocompatibility complex (MHC)-like; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin domain of neonatal Fc receptor (FcRn). FcRn performs two distinct functions: the transport of maternal immunoglobulin G (IgG) to pre- or neonatal mammals which provides passive immunity and protection of IgG from normal serum protein catabolism. FcRn is related to class I MHC proteins, but lacks a functional peptide binding groove. 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 2462563745  58 EWKEPPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRNGLAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIV 137
Cdd:cd21011     1 EWKEPPSMRLKARPGSPGFSVLTCSAFSFYPPELQLRFLRNGLAAGSGEGDFGPNGDGSFHAWSSLTVKSGDEHHYRCVV 80

                          90
                  ....*....|...
gi 2462563745 138 QHAGLAQPLRVEL 150
Cdd:cd21011    81 QHAGLAQPLTVEL 93

Immunoglobulin domain of Cluster of Differentiation (CD) 1; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin domain of Cluster of Differentiation (CD) 1. CD1 family of transmembrane glycoproteins, are structurally related to the major histocompatibility complex (MHC) proteins and form heterodimers with beta-2-microglobulin. They mediate the presentation of primarily lipid and glycolipid antigens of self or microbial origin to T cells. The human genome contains five CD1 family genes (CD1a, CD1b, CD1c, CD1d, and CD1e) organized in a cluster on chromosome 1. The CD1 family members are thought to differ in their cellular localization and specificity for particular lipid ligands. CD1a localizes to the plasma membrane and to recycling vesicles of the early endocytic system. Alternative splicing results in multiple transcript variants. Immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class I alpha chain. 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. C1-set Ig domains have one beta sheet that is formed by strands A, B, E, and D and the other strands by G, F, C, and C'.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462563745  61 EPPSMRLKARPSS-PGFSVLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIV 137
Cdd:cd21029     1 VKPRVRLSSRPSPgDGHLQLSCHVTGFYPRPIEVTWLRDGqeQMDGTQSGGILPNHDGTYQLRKTLDIAPGEGAGYSCRV 80

                          90
                  ....*....|.
gi 2462563745 138 QHAGLAQPLRV 148
Cdd:cd21029    81 DHSSLKQDLIV 91

Immunoglobulin Constant-1 (C1)-set domain; The members here are composed of C1-set domains, classical Ig-like domains resembling the antibody constant domain. Members of the IgC1 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, while the IgC domain is involved in oligomerization and molecular interactions. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other strands by G, F, C, and C'.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462563745  68 KARPSSPGFSVLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDE---HHYCCIVQHAGL 142
Cdd:cd00098     8 SPEEKGGGKVTLVCLVSGFYPKDITVTWLKNGvpLTSGVSTSSPVEPNDGTYSVTSSLTVPPSDWdegATYTCVVTHESL 87

                  ....*...
gi 2462563745 143 AQPLRVEL 150
Cdd:cd00098    88 KSPLSKTW 95

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-1 and similar proteins; member of the C1-set of Ig superfamily (IgSF) domains; Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-1 and similar proteins. Qa-1 presents hydrophobic peptides including Qdm derived from the leader sequence of classical MHC I molecules for immune surveillance by NK cells. Qa-1 bound peptides derived from the TCR Vbeta8.2 of activated T cells also activates CD8+ regulatory T cells to control autoimmunity and maintain self-tolerance. Four allotypes of Qa-1 (Qa-1a-d) are expressed that are highly conserved in sequence but have several variations that could affect peptide binding to Qa-1 or TCR recognition. 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 2462563745  60 KEPPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIV 137
Cdd:cd21013     2 SDPPKAHVTHHPRSEGYVTLRCWALGFYPADITLTWQLNGeeLTQDMEFVETRPAGDGTFQKWASVVVPLGKEQKYTCHV 81

                          90
                  ....*....|....*.
gi 2462563745 138 QHAGLAQPLRVELESP 153
Cdd:cd21013    82 EHEGLPEPLTLRWEPP 97

Immunoglobulin C-Type;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 2462563745   79 LTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEH---HYCCIVQHAGLAQP 145
Cdd:smart00407   4 LVCLVSGFYPPDITVTWLRNGqeVTEGVSTTDPLKNSDGTYFLSSYLTVPASTWEsgdVYTCQVTHEGLKEP 75

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class II beta chain. 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 also 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 has 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 2462563745  60 KEPPSMRL-KARPSSPGFSV-LTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSF--HASSSLTVKSGDEhhY 133
Cdd:cd05766     1 RVQPSVKVsPTKTGPLEHPNlLVCSVTGFYPAEIEVKWFRNGqeETAGVVSTELIPNGDWTFqiLVMLETTPRRGDV--Y 78

                          90
                  ....*....|....*.
gi 2462563745 134 CCIVQHAGLAQPLRVE 149
Cdd:cd05766    79 TCQVEHSSLQSPLTVD 94

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.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462563745  62 PPSMRLKAR-PSSPGFS-VLTCSAFSFYPPELQLRFLRNGL-AAGTGQGDFGPNSDGSFH--ASSSLTVKSGDEhhYCCI 136
Cdd:cd05770     2 TPKVQVYSRfPAENGKPnVLNCYVSGFHPPDIEIRLLKNGVkIEDVEQSDLSFSKDWTFYllKYTEFTPTKGDE--YACR 79

                          90
                  ....*....|....*
gi 2462563745 137 VQHAGLAQPLRVELE 151
Cdd:cd05770    80 VRHNTLSEPKIYKWD 94

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) E; 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) E. HLA-E is the first human class Ib major histocompatibility complex molecule to be crystallized. Like other MHC class I molecules, HLA-E is a heterodimer consisting of an a heavy chain and light chain beta-2-microglobulin. HLA-E is highly conserved and almost nonpolymorphic, and has recently been shown to be the first specialized ligand for natural killer cell receptors. 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 2462563745  61 EPPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRNGLA--AGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQ 138
Cdd:cd21024     4 EPPKTHVTHHPISDHEATLRCWALGFYPAEITLTWQQDGEGhtQDTELVETRPAGDGTFQKWAAVVVPSGEEQRYTCHVQ 83

                  ....*...
gi 2462563745 139 HAGLAQPL 146
Cdd:cd21024    84 HEGLPEPV 91

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) domain of the major histocompatibility complex (MHC) class II alpha chain. 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 also 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 2462563745  78 VLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQHAGLAQPLRV 148
Cdd:cd05767    20 TLICFVDNFFPPVINVTWLRNGqpVTDGVSETVFLPREDHSFRKFSYLPFTPSEGDIYDCRVEHWGLEEPLLK 92

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.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462563745  61 EPPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQ 138
Cdd:cd21014     3 DPPKAHVTHHPRSYGAVTLRCWALGFYPADITLTWQLNGeeLTQDMELVETRPAGDGTFQKWASVVVPLGKEQNYTCHVN 82

                  ....*...
gi 2462563745 139 HAGLAQPL 146
Cdd:cd21014    83 HEGLPEPL 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        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462563745  62 PPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQH 139
Cdd:cd21022     4 PPKTHVTHHPVFDYEATLRCWALGFYPAEIILTWQRDGedQTQDVELVETRPAGDGTFQKWAAVVVPSGEEQRYTCHVQH 83

                  ....*..
gi 2462563745 140 AGLAQPL 146
Cdd:cd21022    84 EGLPEPL 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.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462563745  61 EPPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQ 138
Cdd:cd21025     4 EHPKTHVTHHPVSDHEATLRCWALGFYPAEITLTWQWDGedQTQDTELVETRPAGDGTFQKWAAVVVPSGEEQRYTCHVQ 83

                  ....*...
gi 2462563745 139 HAGLAQPL 146
Cdd:cd21025    84 HEGLPEPL 91

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of MIC-A and MIC-B; 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 MIC-A and MIC-B. MIC-A and MIC-B are homologs that serve as stress-inducible antigens on epithelial and epithelially derived cells. Both serve as ligands for the widely expressed activating immunoreceptor NKG2D, a C-type lectin-like activating immunoreceptor. MIC-B is very similar in structure to MIC-A and likely interacts with NKG2D in an analogous manner. The interdomain flexibility observed in the MIC-A structures, a feature unique to MIC proteins among MHC class I proteins and homologs, is also displayed by MIC-B, with an interdomain relationship intermediate between the two examples of MIC-A structures. Mapping sequence variations onto the structures of MIC-A and MIC-B reveals patterns completely distinct from those displayed by classical MHC class I proteins, with a number of substitutions falling on positions likely to affect interactions with NKG2D, but with other positions lying distant from the NKG2D binding sites or buried within the core of the proteins. 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.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462563745  62 PPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRNG--LAAGTGQ-GDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQ 138
Cdd:cd21017     4 PPMVNVTRSEASEGNITVTCRASGFYPWNITLSWRQDGvsLSHDTQQwGDVLPDGNGTYQTWVATRICQGEEQRFTCYME 83

                  ...
gi 2462563745 139 HAG 141
Cdd:cd21017    84 HSG 86

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of H2-Dd; 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 H2-Dd. Mouse MHC is composed of 11 subclasses. It includes the classical MHC class I (MHC-Ia) that comprises H-2D, H-2K and H-2L subclasses, the non-classical MHC class I (MHCIb) that comprises H-2Q, H-2M and H-2T subclasses, the classical MHC class II (MHC-IIa) that includes H-2A(I-A) and H-2E(I-E) subclasses, and the non-classical MHC class II (MHC-IIb) comprises H-2M and H-2O. H-2K, H-2D, and H-2L are 80 to 90% homologous at the amino acid level yet appear to be involved in different recognition reactions and are differentially expressed on lymphoid cells. 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 2462563745  61 EPPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQ 138
Cdd:cd21020     4 DPPKAHVTHHRRPEGDVTLRCWALGFYPADITLTWQLNGeeLTQEMELVETRPAGDGTFQKWASVVVPLGKEQKYTCHVE 83

                  ....*...
gi 2462563745 139 HAGLAQPL 146
Cdd:cd21020    84 HEGLPEPL 91

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain of histocompatibility antigen (HLA) I-A; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class II alpha chain of histocompatibility antigen (HLA) 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 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 a 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.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462563745  62 PPSMRLKARPSSpgfsvLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQH 139
Cdd:cd21006     9 PKSPVLLGQPNT-----LICFVDNIFPPVINITWLRNSksVTDGVYETSFLVNRDHSFHKLSYLTFIPSDDDIYDCKVEH 83

                  ....*..
gi 2462563745 140 AGLAQPL 146
Cdd:cd21006    84 WGLEEPV 90

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of H-2Kb; 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 H-2Kb. H-2Kb is an alloantigen for the 2C T cell receptor (TCR). H-2Kb forms a complex with beta-2-microglobulin, and a peptide, including VSV-8 (RGYVYNGL), SEV-9 (FAPGNYPAL), and OVA-8 (SIINFEKL). Comparison of the OVA-8, VSV-8, and SEV-9 complexes with H-2Kb indicates that four side chains (Lys-66, Glu-152, Arg-155, and Trp-167) adopt peptide-specific conformations. H-2Kb paralogs include H-2Db, H-2Kbml and H-2KbI1s. 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462563745  79 LTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQHAGLAQPL 146
Cdd:cd21019    21 LRCWALGFYPADITLTWQLNGeeLIQDMELVETRPAGDGTFQKWASVVVPLGKEQYYTCHVYHQGLPEPL 90

Class I Histocompatibility antigen, domains alpha 1 and 2;

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*..
gi 2462563745   1 MNFDLKqgTWGGDWPEALAISQRWQQQDKAAnKELTFLLFSCPHRLREHLERGRGNL 57
Cdd:pfam00129 126 LNEDLR--SWTAADPAAQITKRKWEAAGEAE-RQRAYLEGECVEWLRRYLENGKETL 179

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.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 2462563745  77 SVLTCSAFSFYPPELQLRFLRNGLAAGTGQGDFG--PNSDGSFHASSSLTVKSGDEHHYCCIVQHAGLAQPLRVE 149
Cdd:cd20998    23 NLLVCSVSDFYPGNIEVRWFRNGKEEKTGIVSTGlvRNGDWTFQTLVMLETVPQSGEVYTCQVEHPSLTDPVTVE 97

Class II major histocompatibility complex (MHC) alpha 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 immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class II alpha chain of histocompatibility antigen (HLA) I-E. 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 2462563745  77 SVLTCSAFSFYPPELQLRFLRNG--LAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQHAGLAQPLRVELE 151
Cdd:cd21005    19 NILICFIDKFSPPVVNVTWLRNGrpVTEGVSETVFLPRDDHLFRKFHYLTFLPSTDDFYDCEVDHWGLEEPLRKHWE 95

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain of histocompatibility antigen (HLA) DR; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class II alpha chain of histocompatibility antigen (HLA) DR. MHC class II molecules are encoded by three different loci, HLA-DR, -DQ, and -DP, which are about 70% similar to each other. HLA-DR 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-DRA1 and HLA-DRB1, that are adjacent to each other on chromosome band 6p21.31. Susceptibility to multiple sclerosis and rheumatoid arthritis are associated with the human histocompatibility leukocyte antigen HLA-DR2 and HLA-DR4, respectively. 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 2462563745  77 SVLTCSAFSFYPPELQLRFLRNGLAAGTGQGD--FGPNSDGSFHASSSLTVKSGDEHHYCCIVQHAGLAQPL 146
Cdd:cd21007    19 NVLICFIDKFTPPVVNVTWLRNGKPVTTGVSEtvFLPREDHLFRKFHYLPFLPSTEDVYDCRVEHWGLDEPL 90

HLA class II histocompatibility antigen DO alpha; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the nonclassical MHC class II (MHCII) protein, HLA-DO, which binds HLA-DM and influences the repertoire of peptides presented by MHCII proteins. In complex with HLA-DM, HLA-DO adopts a classical MHCII structure, with alterations near the a subunit's 310 helix. HLA-DO binds to HLA-DM at the same sites implicated in MHCII interaction, and kinetic analysis showed that HLA-DO acts as a competitive inhibitor by acting as a substrate mimic. Though more remains to be elucidated about the function of HLA-DO, its unique distribution in the mammalian body namely, the exclusive expression of HLA-DO in B cells, thymic medullary epithelial cells, and dendritic cells indicate that it may be of physiological importance and has inspired further research. 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 2462563745  62 PPsmRLKARPSSPGF----SVLTCSAFSFYPPELQLRFLRNGLAA--GTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCC 135
Cdd:cd21004     2 PP--RVTVLPKSRVElgqpNILICIVDNIFPPVINITWLRNGQTVteGVAQTSFYSQPDHLFRKFHYLPFVPSAEDVYDC 79

                          90
                  ....*....|..
gi 2462563745 136 IVQHAGLAQPLR 147
Cdd:cd21004    80 KVEHWGLDRPLL 91

Signal-regulatory protein (SIRP) immunoglobulin-like domain 2; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig)-like domain in Signal-Regulatory Protein (SIRP), domain 2 (C1 repeat 1). 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 contain either ITIMs or transmembrane regions that 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, but with much less affinity.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462563745  62 PPSMRLKARPSS---PGFSV-LTCSAFSFYPPELQLRFLRNGLAAGTGQGDFGPNSDG-SFHASSSLTVK--SGDEH-HY 133
Cdd:cd05772     1 KPSQPLVSGPSGratPGQTVsFTCKSHGFSPRDITLKWFKNGNELSALQTTVFPEGDSvSYSVSSTVQVVltKDDVHsQL 80

                          90
                  ....*....|....
gi 2462563745 134 CCIVQHAGLAQPLR 147
Cdd:cd05772    81 TCEVAHVTLQAPLR 94