HLA-DRB1 and rheumatoid arthritis: Since the Seventies, the RA risk has been associated to specific HLA-DRB1 molecules (HLA-DRB1*01, *04, *10) and, more recently, to few variants sharing an amino acid sequence (position 70–74) in the third hypervariable region of HLA-DR β chain known as Shared Epitope (SE) (Table 1) [13].