Life, death, and miracles: Th17 cells in the intestine.

Th17 cells, a distinct subset of CD4(+) T-helper cells, are commonly associated with chronic inflammatory and autoimmune diseases; however, Th17 cells also possess a variety of beneficial functions as they maintain and defend mucosal barriers against pathogens and promote tissue repair. Furthermore, recent findings indicate that Th17 cells can also acquire immunosuppressive functions that protect against inflammatory and auto-immune diseases. A sentinel population of Th17 cells is localized in the intestine in the absence of pathology and, in response to infection, this population expands in number, and can also modulate its functions. This review discusses the beneficial and pathogenic roles played by Th17 cells in the intestine.