Phenotypic analysis of Th cells in colon and peripheral blood in patients with irritable bowel syndrome

Abstract

OBJECTIVE; To analyze the change of Th1/Th2/Th17 in colonic mucosa and peripheral blood in diarrhea-predominant IBS (D-IBS) to uncover the underlying mechanism for the activation of mucosal immune system. Colonic biopsy specimens and peripheral blood were obtained from patients with D-IBS (n = 27) and controls (n = 16). Two different groups were classified on the basis of histological assessment of biopsy specimens from D-IBS patients. One group (14 of 27) had normal conventional histology (IBS), while another group (13 of 27) had nonspecific microscopic inflammation (IBS-A). Flow cytometric detection of intracellular IFN-gamma/IL-4/IL-17 cytokine production was employed to investigate Th1, Th2 and Th17 cells in colonic lamina propria and peripheral blood. Western blot was used to determine the expressions of IL-12, IL-4 and IL-17 in colonic mucosa. The levels of IL-12, IL-4 and IL-17 in peripheral blood were detected by ELISA. In colonic mucosa, the proportion of Th17 increased in IBS-A group as compared with controls [3.60 (4.05) vs 1.25 (3.70), P = 0.045], but not in IBS group. No difference could be observed in the frequencies of Th1 and Th2 in colonic mucosa and peripheral blood. The levels of IL-12, IL4 and IL-17 in IBS and IBS-A showed no difference in either colonic mucosa or peripheral blood. Subgroup of D-IBS showed abnormal conventional histology, implicating the activation of mucosal immune system in pathogenesis. The shift of Th1/Th2/Th17 balance in colonic mucosa showed the enhanced Th17 activity.