Control of TH17 cells occurs in the small intestine

Abstract

Interleukin (IL)-17-producing T helper cells (TH17) are a recently identified CD4+ T cell subset distinct from T helper type 1 (TH1) and T helper type 2 (TH2) cells1. TH17 cells can drive antigen specific autoimmune diseases and are considered the main population of pathogenic T cells driving experimental autoimmune encephalomyelitis (EAE)2, the mouse model for multiple sclerosis. The factors that are needed for the generation of TH17 cells have been well-characterized3–6. However, where and how the immune system controls TH17 cells in vivo remains unclear.Here, by using a model of tolerance induced by CD3-specific antibody, a model of sepsis and influenza A viral infection (H1N1), we show that pro-inflammatory TH17 cells can be redirected to and controlled in the small intestine. TH17-specific IL-17A secretion induced expression of the chemokine CCL20 in the small intestine, facilitating the migration of these cells specifically to the small intestine via the CCR6/CCL20 axis. Moreover, we found that TH17 cells are controlled by two different mechanisms in the small intestine: first, they are eliminated via the intestinal lumen and simultaneously pro-inflammatory TH17 cells acquire a regulatory phenotype with in vitro and in vivo immune-suppressive properties (rTH17). These results identify mechanisms limiting TH17 cell pathogenicity and implicate the gastrointestinal tract as a site for control of TH17 cells.