A recent study by Goyette et al. demonstrated the importance of HLA-DRB1*0103 in both CD and UC by genotyping 7,406 MHC SNPs in 32,000 IBD cases and an equal number of controls (Goyette et al., 2015) The fine resolution of mapping allowed localization of the association signal to specific amino acid substitutions in the MHC molecule which revealed that the causal variants are located within the peptide binding groove and thereby influence antigen presentation directly (Goyette et al., 2015). Here, HLA-DRB1 is linked to inflammatory bowel disease.