CCR6-mediated dendritic cell activation of pathogen-specific T cells in Peyer's patches.

T cell activation by dendritic cells (DCs) is critical to the initiation of adaptive immune responses and protection against pathogens. Here, we demonstrate that a specialized DC subset in Peyer's patches (PPs) mediates the rapid activation of pathogen specific T cells. This DC subset is characterized by the expression of the chemokine receptor CCR6 and is found only in PPs. CCR6(+) DCs were recruited into the dome regions of PPs upon invasion of the follicle associated epithelium (FAE) by an enteric pathogen and were responsible for the rapid local activation of pathogen-specific T cells. CCR6-deficient DCs were unable to respond to bacterial invasion of PPs and failed to initiate T cell activation, resulting in reduced defense against oral infection. Thus, CCR6-dependent regulation of DCs is responsible for localized T cell dependent defense against entero-invasive pathogens.