Induction of lamina propria Th17 cells by intestinal commensal bacteria.

Th17 cells constitute a subset of activated CD4(+) T cells, characterized by their production of interleukin (IL)-17, IL-17F, and IL-22, that play a critical role in host defence against extracellular pathogens. An intriguing feature of these cells is their selective and constitutive presence in the intestinal lamina propria. The development of intestinal Th17 cells is controlled by intestinal commensal bacteria. Recently, segmented filamentous bacterium (SFB) was identified as a specific bacterial taxon that promotes Th17 differentiation in the small intestine of mice. We discuss the recent advances in our understanding of the mechanism of intestinal Th17 synthesis and its potential implications for the treatment of inflammatory bowel diseases.