Essential role of CCR6 in directing activated T cells to the skin during contact hypersensitivity.

CCR6 is expressed in a number of dermatological inflammatory diseases. Here, we report that mice sensitized with the hapten oxazolone had increased numbers of CCR6+ T cells in the draining lymph nodes. Using CCR6-/- mice, we assessed the role of CCR6 on the development of contact hypersensitivity. After hapten sensitization and re-challenge, ear swelling in CCR6-/- animals was reduced 80% as compared with wild-type (WT) control mice. This decreased level of inflammation was not related to an inhibition in T-cell activation, because CCR6-/- lymph node cells from sensitized mice produced threefold higher levels of IFN-gamma in culture than cells from sensitized WT mice and, when these cells were directly injected into the site of hapten challenge, induced a robust inflammatory response. However, intravenous injection of CCR6-/- lymph node cells from sensitized mice were unable to prime naive mice to re-challenge whereas cells from primed WT mice were able to sensitize animals. These results suggest that CCR6 plays an important role in directing the trafficking of activated T cells into the skin and suggests that a CCR6 antagonist could be useful to treat skin-mediated inflammatory reactions.