We chose to examine the influence of HLA-DRB1*04 and HLA-DRB1*01 separately, since HLA-DRB1*04 is more strongly associated with anti-CCP-positive RA than HLA-DRB1*01 (12) (subjects were grouped as illustrated in Supplementary Figure 1; of note, subjects carrying both alleles were included in the analysis of HLA-DRB1*04). The gene discussed is HLA-DRB1; the disease is rheumatoid arthritis.