Indeed, five amino acid positions across three HLA genes (positions 11, 71, and 74 in HLA-DRB1, as well as position 9 in HLA-B and HLA-DPB1) have been shown to collectively explain most of the HLA region’s contribution to seropositive RA in Europeans (8). Here, HLA-DRB1 is linked to rheumatoid arthritis.