The HLA-DRB1 SE was found to be moderately associated with the expression of PTPN22. As can be seen in Figure 2, RA patients carrying two copies of the SE had moderately higher expression of both PTPN22_v4 (P = 0.04) and PTPN22-long forms (P = 0.02) compared to individuals with no or only one copy. This evidence concerns the gene HLA-DRB1 and rheumatoid arthritis.