HLA-DPA1 (Major Histocompatibility Complex, Class II, DP Alpha 1): The HLA-DPA1 gene is a gene that is part of the human leukocyte antigen (HLA) system, which plays a critical role in immune function. It is involved in presenting peptides from extracellular proteins to T cells, helping regulate immune responses. Variations in HLA-DPA1 are important for adaptive immunity and are linked to autoimmune diseases, transplant compatibility, and vaccine response.