Abstract: To observe the changes of regulatory T cells (Treg cells) in peripheral blood in rat model with post infectious irritable bowel syndrome (PIIBS) and investigate the role of Treg cells in its pathogenesis. Methods: A total of 16 female rats were divided into model and control groups, who were given shigella flexneri by gavage and saline by gavage, respectively. After the bowel inflammation had been induced for 16～22 days, all rats were treated with colonrectal balloon distention; the contraction of enteric smooth muscle were measured in vitro and the proportion of Treg cells in peripheral blood was detected by using flow cytometry analysis. Results: In model group, the perceptual threshold decreased and the tension integral of enteric smooth muscle increased greatly compared with the results from control group（P＜0.05）, while no obvious histological changes had been observed, suggesting rat model of PIIBS had been successfully established; the value of Treg/CD4+T in peripheral blood decreased significantly compared with the result from control group（P＜0.05）. Conclusion: Bowel functional disorder is prolonged after acute enteric inflammation has disappeared. Abnormal immunoregulation takes account for the pathogenesis of PIIBS.

Key words: Irritable bowel syndrome, T regulatory cell, Infection, Bowel functional disorder