HLA-DRB1 and rheumatoid arthritis: Specifically, we focused on the HLA DRB1*04 alleles (*0401, 0404, 0405 and 0408) and the closely related DRB1*1001 genes most strongly associated with RA (odds ratios > 4.2) (27), and refer to carriers of these alleles as risk RA HLA and non-carriers as non-risk RA HLA.