HLA-DRB1 and rheumatoid arthritis: In particular, a common amino acid sequence at position 70‐74 of the HLA‐DRB1 molecule (the so‐called “shared epitope,” HLA‐SE) was shown to be associated with disease.53 Notably, HLA‐SE alleles are only associated with ACPA‐positive RA, but not with ACPA‐negative RA,54 which indicates a strong link between HLA‐SE and the ACPA response in RA patients.