HLA-DRB1 and rheumatoid arthritis: This association was first suggested more than 30 years ago [3] and was elaborated 10 years later by Gregersen and colleagues [4], who demonstrated that RA was associated with several HLA-DRB1 alleles (DRB1*0101, DRB1*0102, DRB1*0401, DRB1*0404, DRB1*0405, DRB1*0408, DRB1*1001, and DRB1*1402) encoding the RAA sequence of amino acids at positions 72 to 74 in the third hypervariable region of the DRβ1 chain, known as the shared epitope (SE).