HLA-C and rheumatoid arthritis: Compared to the MR analysis without MHC loci, the same causal association between celiac disease and sepsis (OR = 1.019, 95% CI = 1.008–1.030, p = 5.000E-4) was observed in the MR analysis including SNPs at MHC loci, except for RA and T1DM (Additional file 2: Fig. S1, Additional file 3: Table S6).