From this observation based on the binding properties of one peptide from vimentin and its one citrullinated variant to 8 different HLA-DR molecules, came the hypothesis that shared epitope positive HLA-DR molecules bound citrullinated peptides better than shared epitope negative HLA-DR molecules, thus explaining the RA, ACPA, HLA-DR association (6). The gene discussed is PRTN3; the disease is rheumatoid arthritis.