Human leukocyte antigen class II histocompatibility antigen (MHC class II) (HLA class II)

Human leukocyte antigen (HLA) class II histocompatibility antigens are a family of heterodimeric cell surface glycoproteins, consisting of an alpha and a beta chain, that are primarily expressed on professional antigen-presenting cells such as dendritic cells, B cells, and macrophages [1][2]. Their fundamental biological role is to bind peptides derived from extracellular proteins and present them to CD4+ T-cell receptors, thereby orchestrating the adaptive immune response [2][3]. Because they are central to the recognition of 'self' versus 'non-self,' these molecules are the primary genetic determinants of susceptibility to numerous autoimmune conditions, including rheumatoid arthritis, type 1 diabetes, and multiple sclerosis [4][5]. In the therapeutic landscape, HLA class II molecules are targeted by drugs like glatiramer acetate, which acts as a peptide decoy to modulate T-cell responses in multiple sclerosis [5]. Furthermore, they are critical in organ transplantation, where mismatching between donor and recipient HLA class II alleles can lead to acute or chronic graft rejection [3][6]. Research is also expanding into the role of these antigens in oncology, where their expression on tumor cells can serve as a biomarker for response to immunotherapy [6]. Citations: [1] UniProt: MHC class II (KW-0475). [2] Janeway's Immunobiology, 9th ed. [3] StatPearls: Major Histocompatibility Complex (MHC): https://www.ncbi.nlm.nih.gov/books/NBK542247/ [4] NIH MedlinePlus: HLA-DRB1. [5] National MS Society: Glatiramer Acetate Mechanism: https://pubmed.ncbi.nlm.nih.gov/11252934/ [6] Journal of Clinical Investigation: HLA Class II in Cancer Immunotherapy: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6481617/

Other names

Major histocompatibility complex class IIMHC class IIHLA-DRHLA-DPHLA-DQMHC-II

Drugs targeting this molecule typically work by binding to the peptide-binding cleft to compete with autoantigens, blocking the interaction between the MHC complex and the T-cell receptor (TCR), or by downregulating the surface expression of the antigen-presenting complex to reduce T-cell activation [3][5].