Interestingly, leucine residue, which encodes the classical HLA-DRB1*01 alleles, was commonly found among the individuals of European ancestry (> 10% in both RA cases and control group), but was found in less than 5% of the Malay and Indian ethnic groups, and was absent in the Chinese RA cases and controls. This evidence concerns the gene HLA-DRB1 and rheumatoid arthritis.