Major histocompatibility complex, class II, DR alpha chain (HLA-DRA)

Major histocompatibility complex, class II, DR alpha chain (HLA-DRA) is the invariant alpha subunit of the HLA-DR antigen-presenting heterodimer, a key component of MHC class II molecules[1][2][3]. HLA-DRA pairs with beta chains encoded by DRB1, DRB3, DRB4, or DRB5 genes to form functional DR molecules on antigen-presenting cells (APCs) such as B lymphocytes, dendritic cells, and macrophages[1][2][3]. The main function of the HLA-DR heterodimer is to bind and present extracellular protein-derived peptides to CD4+ T cells, initiating and regulating the adaptive immune response[1][2][3]. HLA-DRA is largely non-polymorphic compared to the beta chain but is essential for heterodimer stability, surface expression, and immune function[5]. Dysregulation or genetic variation of HLA-DRA is implicated in autoimmune diseases, infection susceptibility, cancer progression, neuroinflammation, and adverse drug reactions[2][3]. Its expression is often used as a biomarker for immune cell function and disease prognosis in various clinical contexts[2].

Other names

HLA class II histocompatibility antigen, DR alpha chainHLA-DRA1MHC class II antigen DRAHistocompatibility antigen HLA-DR alpha

Presentation of peptide antigens to CD4+ T cells, leading to immune activation or tolerance Regulation of T-helper cell differentiation and effector functions