CD11b+ migratory dendritic cells mediate CD8 T cell cross-priming and cutaneous imprinting after topical immunization

Topical antigen application is a focus of current vaccine research. This immunization route mimics natural antigen exposure across a barrier tissue and generates T cells imprinted for skin-selective homing. Soluble antigens introduced through this route require cross-presentation by DC to generate CD8 T cell responses. Here we have explored the relative contribution of various skin-derived DC subsets to cross-priming and skin-selective imprinting. In our model, DC acquire soluble Ag in vivo from immunized murine skin for cross-presentation to naïve CD8 T cells ex vivo. We find CD11b(+) migratory DC to be the relevant cross-priming DC in this model. Both Langerin(+) and Langerin(-) CD11b(+) migratory DC can cross-present antigen in our system, but only the Langerin+ subset can induce expression of the skin-selective addressin E-selectin ligand. Thus, the CD11b(+) Langerin(+) migratory DC population, comprised primarily of Langerhans cells, both cross-primes naïve CD8 T cells and imprints them with skin-homing capabilities.