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‐α and IL‐1β 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.