HLA-DRB1 is a gene that encodes a part of the human leukocyte antigen (HLA) class II molecule, which plays a crucial role in the immune system by presenting peptides to CD4+ T cells. Its significance lies in its association with autoimmune diseases, particularly rheumatoid arthritis and multiple sclerosis, where specific alleles can increase susceptibility. Understanding HLA-DRB1 variants aids in risk assessment and personalised treatment strategies for affected patients.