HLA-DQA2 (Human Leukocyte Antigen DQ Alpha 2): HLA-DQA2 is a gene within the HLA complex that plays a central role in regulating the immune system through antigen presentation. It encodes an alpha chain that pairs with a beta chain to form the HLA-DQ molecule, which presents foreign antigens to T cells to initiate immune responses. Variations in HLA-DQA2 are associated with susceptibility to certain autoimmune diseases, emphasising its significance in immune tolerance and autoimmunity.