Increased number of FoxP3+CD4+ regulatory T cells in inflammatory bowel disease.

FoxP3 is a member of the forkhead/winged helix family of transcription factors and plays a critical role in the development and function of CD4+CD25+ regulatory T cells (Tregs). In this study, we performed an immunohistochemical evaluation of FoxP3-expressing cells in inflammatory bowel disease (IBD) mucosa. Mucosal FoxP3 expression was evaluated by immunohistochemistry in samples from normal (n=30), ulcerative colitis (UC) (n=53) and Crohn's disease (CD) (n=24) mucosa. There were no FoxP3-immunopositive cells in the normal colonic mucosa. In contrast, FoxP3-immunopositive cells were significantly increased in the inflamed regions of patients with active UC and CD. FoxP3-immunopositive cells completely coincided with some of the CD4-positive T cells. In conclusion, FoxP3-immunopositive Tregs were expanded in the inflamed mucosa of IBD patients. This suggests that these cells have impaired regulatory functions in the IBD mucosa.