Activated NKT cells increase dendritic cell migration and enhance CD8+ T cell responses in the skin.

Activated NKT cells produce cytokines such as IL-4 and IFN-gamma that function locally to influence the strength and functional development of antigen-specific T cells. Here we identify an alternative mechanism by which NKT cells influence the strength of T cell responses: through modulation of peripheral dendritic cell (DC) trafficking. NKT cell activation with alpha-galactosylceramide induced high systemic levels of TNF-alpha that mediated increased DC migration from skin to draining lymph nodes. This increased DC trafficking led to a threefold increase in effector T cell priming and in the immune response elicited to antigen challenge when alpha-galactosylceramide was given at the time of immunization of the skin. These studies provide important implications for the use of NKT cell activation strategies to manipulate T cell-mediated responses including responses to cutaneous tumors and graft vs. host disease.