In RA samples, the average relative mRNA expression in IFN-γ in samples with MAP presence and PTPN2:rs478582 (N = 6) was 0.39 ± 0.33 compared to 0.21 ±0.18 (N = 8) in RA samples without MAP presence and without the SNP. Here, PTPN2 is linked to rheumatoid arthritis.