The expression of the anti-inflammatory cytokine IL-10 in the mucosal biopsy of IBS patients was significantly lower than in the control group also in all the examined biopsy sites: duodenum (1.9 ± 0.3 versus 3.9 ± 0.5 points, respectively); ileum (1.8 ± 0.4 and 4.0 ± 0.0); cecum (1.7 ± 0.4 and 4.5 ± 0.8), and sigmoid colon (1.7 ± 0.5 and 4.5 ± 0.8; p < 0.0001 for all localizations; Fig 3). This evidence concerns the gene IL10 and irritable bowel syndrome.