HLA-DRB1 and rheumatoid arthritis: In line with results reported previously, the presence of the HLA-DRB1 SE was found to have no effect on the association of the PTPN22 1858T allele with the disease, since the frequencies of the PTPN22 1858T allele in RA patients and controls and the resulting ORs in the subgroups with zero, one or two copies of the shared epitope were comparable (OR 2.15, p = 0.007; OR 2.59, p < 0.001; and OR 2.0, p = not significant).