HLA-DRB1 and rheumatoid arthritis: In this context, HLA-DRB1*03:01, which was revealed to be protective in our cohort, has been identified as a primary driver of HLA-DRB1 associations in second-generation anti-cyclic citrullinated peptide (CCP2) negative RA patients, but not in CCP2-positive RA patients, demonstrating similar patterns to HLA-B/Asp-9 (51, 54).