Major Histocompatibility Complex Class II DR Beta 3 (MHCDRb3)

Class II major histocompatibility complex molecules present antigens to CD4 -positive cells. Human class II MHC molecules are of 3 major isotypes, HLA-DR, HLA-DP, and HLA-DQ , each of which consists of an alpha and a beta chain. Both the alpha and beta chains of HLA-DP and HLA-DQ are polymorphic, whereas HLA-DR alpha is invariant and HLA-DR beta is polymorphic. Thus, differences in the HLA-DR beta chain account for different peptide-binding motifs of HLA-DR molecules. The most highly expressed HLA-DR beta chain is encoded by the extremely polymorphic HLA-DRB1 gene. Most of the alternate beta chain genes linked to HLA-DRB1 are pseudogenes, but HLA-DRB3, HLA-DRB4, and HLA-DRB5 encode functional proteins. HLA-DRB3 is also known as HLA-DR52 and has 3 major alleles: DRB3*0101 (DR52a), DRB3*0202 (DR52b), and DRB3*0301 (DR52c) .