Flagellin stimulation of intestinal epithelial cells triggers CCL20-mediated migration of dendritic cells

Enteropathogenic bacteria elicit mucosal innate and adaptive immune respons es. We investigated whether gut epithelial cells played a role in triggerin g an adaptive immune response by recruiting dendritic cells (DCs). Immature DCs are selectively attracted by the CCL20 chemokine. The expression of th e CCL20 gene in human intestinal epithelial cell lines was up-regulated by pathogenic bacteria, including Salmonella species, but not by indigenous ba cteria of the intestinal flora. The Salmonella machinery for epithelial cel l invasion was not required for CCL20 gene activation. Flagellin but not th e lipopolysaccharide was found to be the Salmonella factor responsible for stimulation of epithelial CCL20 production. CCL20 in turn triggered a speci fic migration of immature DCs. Our data show that crosstalk between bacteri al flagellin and epithelial cells is essential for the recruitment of DCs, a mechanism that could be instrumental to initiate adaptive immune response s in the gut.