HLA-DRB1 and primary biliary cholangitis: We focussed on the top three amino acid residues (HLA-DPβ1 11L, HLA-DRβ1 74L, HLA-DQβ1 57D) identified through stepwise regression (Table 2), all of which showed strong marginal association with PBC, and we modelled HLA molecules corresponding to alleles showing significant marginal association with PBC (Table 1) that either carried or did not carry the associated amino acid residue.