HLA-DRB1 and systemic lupus erythematosus: These analyses demonstrated that the observed association signals at rs2523589, rs1052486, and rs605203 were predominantly dependent upon the association at rs419788, and suggested that there are two major independent association signals in the MHC in UK SLE: HLA-DRB1 and rs419788. The independence of the association signals at HLA-DRB1 and rs419788 is further supported by the observation that there is only modest LD between these two (r2 = 0.24).