Functional heterogeneity of gut-resident regulatory T cells.

Regulatory T cells (Treg cells) have a central role in the maintenance of intestinal homeostasis by restraining inappropriate immune responses in the healthy gut. Although distinct intestinal immune cell populations have been described to exhibit regulatory activity, several genetic and functional studies provided a strong evidence for a pivotal role of forkhead box P3 (Foxp3)+ CD4+ Treg cells in prevention of dysregulated mucosal immune reactions and development of chronic immunological disorders such as celiac disease, food allergies and inflammatory bowel disease. Treg cells provide an important layer of intestinal defense by suppressing immune responses against innocuous food and commensal-derived antigens. Recent functional studies suggest that Treg cells are also involved in several other processes such as controlling microbial diversity in the gut, immunoglobulin A selection and supporting tissue repair in response to intestinal tissue damage. A better understanding of the functional heterogeneity as well as of the molecular signals, which regulate distinct intestinal Treg cell subsets, will encourage strategies aimed at transplanting the optimal Treg cell subset for cellular therapy in humans.