HLA-DRB1 and ankylosing spondylitis: Associations between certain HLA alleles and autoimmune diseases, such as HLA‐DRB1 for rheumatoid arthritis, HLA‐B51 for Behcet's disease, HLA‐B27 for ankylosing spondylitis, HLA‐DQ2/DQ8 for celiac disease, and HLA‐DQB1*06:02 for narcolepsy, are widely known.