Human leukocyte antigen molecule on antigen-presenting cell (HLA (context: on APCs refers primarily to HLA Class II))

Human leukocyte antigen molecules on antigen-presenting cells (APCs) refer predominantly to HLA class II molecules (including HLA-DR, HLA-DP, and HLA-DQ), which are cell surface glycoproteins encoded in the major histocompatibility complex on chromosome 6[1][4][5][6]. These molecules are highly polymorphic and expressed primarily on professional APCs such as dendritic cells, macrophages, and B cells, although expression can be induced in other cells under certain conditions[1][6]. Their main function is to present peptides derived from extracellular proteins (exogenous antigens) to CD4+ T helper cells, leading to activation of adaptive immune responses and facilitating self/non-self recognition[1][2][3][5][6]. Variants in HLA genes are strongly associated with susceptibility or resistance to various autoimmune diseases, infection outcomes, and play a key role in transplantation compatibility and the risk of rejection[3][5][6]. The extreme polymorphism of HLA molecules underlies both their critical role in pathogen defense and their involvement in diverse immunological diseases[1][3][7]. Therapeutic targeting is primarily indirect, with immunomodulatory drugs or monoclonal antibodies used in the context of transplantation or autoimmune disease, but direct targeting remains a research area due to the risk of widespread immune disruption[6][7]. Detection of specific HLA alleles or antibodies is used extensively as a biomarker in the clinic for disease risk assessment and transplant matching.

Other names

Human leukocyte antigenMajor histocompatibility complex (MHC, human)HLA Class II moleculeMHC class IIHLA-DRHLA-DPHLA-DQ

Monoclonal antibodies: Blockade of antigen presentation or depletion of HLA-expressing cells Indirectly: Modulation of immune cell activation, transplant desensitization, or immune tolerance induction via altered antigen presentation