For example, certain HLA‐DRB1 allomorphs are well known to present citrullinated epitopes derived from autoantigens vimentin and aggrecan because citrulline can be accommodated within the electropositive P4 pocket of HLA‐DRB1*04:01 and HLA‐DRB1*04:04, but not in the electronegative P4 pocket of the RA‐resistant HLA‐DRB1*04:02 form.70 Here, HLA-DRB1 is linked to rheumatoid arthritis.