Major histocompatibility complex, class II, DR beta 4 (HLA-DRB4)

Major histocompatibility complex, class II, DR beta 4 is a membrane-bound heterodimeric protein composed of an alpha (DRA) and a beta (DRB4) chain, primarily expressed on antigen-presenting cells (APCs) such as B lymphocytes, dendritic cells, and macrophages. It binds exogenous peptide antigens from degraded proteins and presents them to CD4+ helper T cells, a key process in adaptive immunity. HLA-DRB4 exhibits polymorphisms that dictate binding specificity for different peptide antigens and is a secondary DR beta chain found associated with certain HLA haplotypes such as DR4, DR7, and DR9. Notably, the DRB4 allele (especially DRB4*01:01) is strongly linked to susceptibility to autoimmune diseases, including type 1 diabetes, by presenting unique self-epitopes to autoreactive T cells. HLA-DRB4 expression and its polymorphisms are routinely assessed in transplantation medicine due to their effect on immune compatibility and graft survival.

Other names

HLA class II histocompatibility antigen, DR beta 4 chainHLA-DRB4MHC class II antigen DRB4DRB4DR-4DR4HLA-DR4B

Drugs may inhibit or alter antigen presentation, T cell activation, or the immune response (e.g., monoclonal antibodies blocking MHC II-TCR interaction, immunosuppressants reducing surface expression)