In RA samples, the average relative mRNA expression of IFN-γ in samples with PTPN2:rs478582 heterozygous (TC) or minor (CC) allele was 0.33 ± 0.32 (N = 22), compared to 0.22 ± 0.16 in 13 normal (TT) RA samples (Figure 5A). This evidence concerns the gene PTPN2 and rheumatoid arthritis.