HLA-DRB1 and rheumatoid arthritis: We choose to study genes HLA-DRB1 using its shared-epitope alleles and KCNB1. The relationship between HLA-DRB1 and increased risk for rheumatoid arthritis has been studied for 20 years, and several high risk alleles of HLA-DRB1 are treated as shared-epitope alleles [3,4], which are used widely in association study for rheumatoid arthritis [5].