HLA class II histocompatibility antigen (HLA-II)

HLA class II histocompatibility antigens are a group of cell surface glycoproteins primarily expressed on professional antigen-presenting cells (APCs), such as dendritic cells, macrophages, and B cells. These molecules play a fundamental role in the adaptive immune system by presenting processed exogenous peptides to CD4+ T helper cells, which is essential for initiating and coordinating immune responses (StatPearls, PMID: 30725800). The HLA class II complex is composed of alpha and beta chains encoded by the HLA-DR, HLA-DQ, and HLA-DP loci within the major histocompatibility complex (MHC) region on chromosome 6. Genetic variations in these antigens are the most significant risk factors for various autoimmune disorders, including rheumatoid arthritis and type 1 diabetes, where specific alleles mistakenly present self-antigens to T cells (PubMed, PMID: 24685124). In oncology, HLA class II molecules serve as the primary ligand for the inhibitory checkpoint receptor LAG-3, making them critical targets for enhancing anti-tumor immunity (PubMed, PMID: 32883714). Therapeutic strategies include the use of glatiramer acetate to compete for peptide binding in multiple sclerosis and LAG-3-targeting agents like eftilagimod alpha or relatlimab to modulate T-cell activity in cancer (FDA, Opdualag Label). Understanding the expression and polymorphism of these antigens is vital for predicting transplant compatibility and patient responses to immunotherapies.

Other names

MHC class IIMajor histocompatibility complex class IIHLA-DRHLA-DQHLA-DPHuman leukocyte antigen class II

Competitive inhibition of peptide binding, LAG-3 checkpoint blockade, antigen presentation modulation, and direct antibody-mediated cytotoxicity.