Human leukocyte antigen DR isotype (HLA-DR) (HLA-DR)

HLA-DR2 and HLA-DR4 are allelic variants of the HLA-DR isotype, a major histocompatibility complex class II cell surface receptor that is heterodimeric and consists of α and β polypeptide chains encoded by the HLA-DRA and HLA-DRB loci, respectively. These molecules are primarily expressed on professional antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B cells, and are essential for the presentation of processed peptide antigens to CD4+ T-helper lymphocytes. Distinct allelic variants like HLA-DR2 (DRB1*1501) and HLA-DR4 (DRB1*0401) are strongly associated with increased susceptibility to autoimmune diseases, including multiple sclerosis (DR2) and rheumatoid arthritis (DR4), based on their unique peptide-binding properties and the immune responses they elicit. The functional relevance of HLA-DR in immunity, autoimmunity, and transplantation biology makes it an important therapeutic, diagnostic, and prognostic target. Peptide binding in the antigen-binding groove of HLA-DR triggers downstream T-cell activation, which can result in immune defense or, in cases of loss of tolerance, autoimmunity.

Other names

HLA-DR2 (DRB1*1501)HLA-DR4 (DRB1*0401)HLA-DRB1Major histocompatibility complex class II DRDR antigen

Drugs act by interfering with antigen presentation (generally by inhibiting T cell activation or depleting antigen-presenting cells)