The HLA-DRB1 gene is the most potent disease susceptibility gene, explaining 30–50% of the genetic risk of RA, and a specific sequence at positions 70–74 of the HLA-DRB1 allele is called a shared epitope (SE) and thought to be involved in the onset and pathology of RA4,5. This evidence concerns the gene HLA-DRB1 and rheumatoid arthritis.