In RA patients, the average relative mRNA expression in IFN-γ in samples with MAP presence and the PTPN22:rs2476601 SNP (N = 5) was 0.15 ± 0.07 compared to 0.27 ± 0.24 in RA patients without MAP presence and without the SNP (N = 17). This evidence concerns the gene PTPN22 and rheumatoid arthritis.