HLA-DRB1 and rheumatoid arthritis: For the HLA-DRB1 alleles, we selected six alleles that were significantly associated with RA risk in a comprehensive review article [62] using the largest collection of relevant articles: HLA-DRB1*01:01, DRB1*09:01, DRB1*10:01, DRB1*04:04, DRB1*04:01, and DRB1*04:05.