CCR6 regulates the migration and effector function of Th17 cells in the gut (96.2)

Abstract

Abstract T helper cells that produce IL-17 (Th17 cells) play important roles in regulation of immunity to bacteria and fungi and can cause organ-specific inflammation. The intestine is a tissue where Th17 cells are highly enriched, but migration and trafficking receptors of Th17 cells to the intestine have been unclear. It has been established that CCR6 is the signature chemokine receptor for Th17 cells but the role of this trafficking receptor in Th17 cell trafficking to the intestine has not been determined. We report here that Th17 cells preferentially migrate to the intestine and associated-lymphoid tissues, and CCR6 is the homing receptor important for Th17 cell migration to certain tissue microenvironments of the intestine where its ligand CCL20 is highly expressed. We determined the function of CCR6 of Th17 cells by comparing the migration and effector function of Th17 cells derived from wild type and CCR6-deficient mice. CCR6-deficient Th17 cells were defective in migration to Peyer's patches and small intestine but their migration to the large intestine was normal. Surprisingly, administration of CCR6-deficient Th17 cells into severe combined immunodeficiency (SCID) mice led to excessive intestinal inflammation. Following the administration of Th17 cells, we found that Th17 cells fail to propagate in the gut in the absence of CCR6 and transdifferentiate into inflammatory Th1 cells. In addition, CCR6 deficiency led to aberrantly wide-spread effector T cells in the inflamed intestine of the SCID mice. Finally, we found that the expression of CCR6 by Th17 cells is induced by TGF-β1 but suppressed by IL-2 in vitro and in vivo. Taken together, we conclude that CCR6 is a key trafficking receptor that regulates the migration and effector function of Th17 cells in the intestine.