Synonyms:
CD74; DHLAG; DR-4; DR4; DRB1; DRB4; DRw10; HLA-DR1B; HLA-DR3B; HLA-DR4B; HLA-DRA; HLA-DRA1; HLA-DRB; HLA-DRB1; HLA-DRB3; HLA-DRB4; HLA-DRB5; HLADG; Ia-GAMMA; II; MLRW; SS1; CD; CELIAC 1; CELIAC1; DP beta 1 chain; DP(W4) beta chain; DPB1; DPB1_HUMAN; DQ A1; FLJ27088; FLJ27328; GSE; HLA class II histocompatibility antigen; HLA class II histocompatibility antigen DR 1 beta; HLA class II histocompatibility antigen DR alpha; HLA class II histocompatibility antigen DR alpha chain; HLA DP histocompatibility type beta 1 subunit; HLA DP1B; HLA DPB1; HLA DQA; HLA DQA1; HLA DQB; HLA DQB1; HLA DR1B; HLA DR3B; HLA DR4B; HLA DRA; HLA DRA1; HLA DRB1; HLA DRB3; HLA DRB4; HLA DRB5; HLA-DPB1; IDDM 1; IDDM1; Major histocompatibility complex class II DP beta 1; Major histocompatibility complex class II DQ alpha 1; Major histocompatibility complex class II DQ beta 1; Major histocompatibility complex class II DR alpha; Major histocompatibility complex class II DR beta 1; Major histocompatibility complex class II DR beta 3; Major histocompatibility complex class II DR beta 4; Major histocompatibility complex class II DR beta 5; MGC117330; MHC class II antigen DPB1; MHC class II antigen DRA; MHC class II HLA DQ alpha 1; MHC class II HLA DR beta 1; MHC class II HLA DR beta 3; MHC DPB1; MHC DQ beta; MHC HLA DPB1; MHC HLA DQ alpha.
Introduction:
HLA-DR, like other MHC class II molecules, is a transmembrane glycoprotein composed of a 36 kDa alpha chain (DRA) and 27 kDa beta chain (DRB). The alpha chain gene contains 5 exons. Exon 1 encodes the leader peptide, exons 2 and 3 encode the two extracellular domains, and exon 4 encodes the transmembrane domain and the cytoplasmic tail. DRA does not have polymorphisms in the peptide binding part and acts as the sole alpha chain for DRB1, DRB3, DRB4 and DRB5. Within the DR molecule the beta chain contains all the polymorphisms specifying the peptide binding specificities. Hundreds of DRB1 alleles have been described and typing for these polymorphisms is routinely done for bone marrow and kidney transplantation. HLA-DR is expressed primarily on antigen presenting cells such as B lymphocytes, monocytes, macrophages, thymic epithelial cells and activated T lymphocytes. Three loci, DR, DQ and DP, encode the major expressed products of the human class II region. The human MHC class II molecules bind intracellularly processed peptides, present them to T-helper cells, and have a critical role in the initiation of the immune response.