A homologous molecular structure, consisting of a glutamic acid, glutamine, arginine, arginine, alanine, and alanine “EQRRAA” amino acid sequence (present in some subtypes of HLA-DRβ1 molecules, such as HLA-DRβ1*0401 and HLA-DRβ1*0404, but not in others such as HLA-DRβ1*0402) has been described in patients with RA and was given the name of “shared epitope” [7]. This evidence concerns the gene HLA-DRB1 and rheumatoid arthritis.