HLA-DRB1 and rheumatoid arthritis: The HLA-DRB1 alleles commonly associated with RA encode amino acid sequences referred to as the shared epitope (SE); these sequences are located at amino acids 70–74 (e.g., QKRAA, QRRAA, RRRAA) in the third hypervariable region of the β-chain (particularly DRBpos-11) [2, 6, 7].