Maintenance of small intestinal and colonic tolerance by IL-10-producing regulatory T cell subsets

The intestinal mucosa is continuously exposed to harmless exogenous antigens derived from food proteins and microbiota. Continuous surveillance by suppressive regulatory T cells prevents inflammatory responses to these antigens thereby maintaining intestinal homeostasis. The nature of the antigenic pressure varies at different locations of the intestinal tract. In agreement with this strong microenvironmental control, small intestinal and colonic regulatory T cell homeostasis varies considerably. In this review, we summarize the substantial advances that have been made in dissecting the phenotype and function of intestinal regulatory T cells, discuss how microbiota can modulate the intestinal regulatory T cell pool and review the crucial role of the immunoregulatory cytokine interleukin-10 (IL-10) in shaping and maintenance of mucosal tolerance.