The genetic susceptibility of RA is strongly associated with the human leukocyte antigen (HLA) loci, specifically the HLA-DRB1 genes, which encode an HLA-DR β-chain possessing a common five-amino-acid sequence of either QKRAA, QRRAA, or RRRAA at positions 70 to 74 (12). This evidence concerns the gene HLA-DRB1 and rheumatoid arthritis.