The results of RT-PCR assays showed that IFN-γ levels were significantly higher in the intestinal mucosa of PI-IBS patients (0.47 ± 0.02) than that in non-PI-IBS patients (0.32 ± 0.02) or healthy people (0.31 ± 0.02) (both P < 0.05), but there was no significant difference between the non-PI-IBS and control groups (P > 0.05). Here, IFNG is linked to irritable bowel syndrome.