Immune response in irritable bowel syndrome: A systematic review of systemic and mucosal inflammatory mediators

OBJECTIVE: To systematically review the available data on cytokine and immune cells in the peripheral blood and mucosal biopsy samples from patients with irritable bowel syndrome (IBS). METHODS: From a review of the literature, data on cytokines and immune cells that had been assayed in at least three independent studies were collated and trends examined. RESULTS: Levels of interleukin (IL)-10 tended to be decreased and those of IL-6, IL-8, tumor necrosis factor-alpha and IL-1 beta increased in the systemic circulation in IBS, while in the mucosa, IL-10 was decreased and IL-8, mast cells, enterochromaffin cells and CD3(+) T lymphocytes were increased. However, these findings were not consistent across all studies and, in some instances, were limited to certain IBS sub-populations. CONCLUSIONS: The interpretation of this literature is limited by several factors, such as the intrinsic heterogeneity of IBS and a lack of standardization in study design. While a number of intriguing immunological observations have been made in IBS, more work is needed before a compelling case can be made for a role for immune-mediated events in the etiology of IBS.