Trafficking of regulatory T cells in the intestinal immune system.

Intestinal tolerance toward dietary antigens and the microbiota critically depends on regulatory T cells (T(reg) cells). To exert their function, T(reg) cells need to get into the proximity of their target cells foremost within lymphoid organs and the lamina propria in the small and large intestines. Thus, T(reg)-cell-mediated immunosuppression is intrinsically linked to cell migration and localization. However, the gut lamina propria not only constitutes an effector site but also actively influences T(reg)-cell function. In particular, gut-resident macrophages take an active role in shaping the T(reg)-cell pool. Here, the author summarizes recent observations to suggest that T(reg)-cell migration not only directs cells to sites of immunosuppression but also allows for the coordinated shaping of the T(reg)-cell population.