HLA-DRB1*04 is a risk factor in both RA and T1D (5, 24), while HLA-DRB1*1501/DQB1*0602 have an opposite effect in MS and T1D, with an increased risk for MS but a protective role in T1D (5, 87). Here, HLA-DRB1 is linked to rheumatoid arthritis.