HLA-DRB1 and rheumatoid arthritis: A major breakthrough was the identification of a sequence of five amino acids in residues 70–74 (QKRAA, QRRAA, RRRAA) in the third hypervariable region of the DRß1-chain, encoded by the HLA-DRB1 gene, that was highly preserved in risk alleles for RA and was therefore named shared epitope (SE) (19, 21).