Migratory dendritic cells transfer antigen to a lymph node-resident dendritic cell population for efficient CTL priming.

Skin dendritic cells (DCs) are thought to act as key initiators of local T cell immunity. Here we show that after skin infection with herpes simplex virus (HSV), cytotoxic T lymphocyte (CTL) activation required MHC class I-restricted presentation by nonmigratory CD8(+) DCs rather than skin-derived DCs. Despite a lack of direct presentation by migratory DCs, blocking their egress from infected skin substantially inhibited class I-restricted presentation and HSV-specific CTL responses. These results support the argument for initial transport of antigen by migrating DCs, followed by its transfer to the lymphoid-resident DCs for presentation and CTL priming. Given that relatively robust CTL responses were seen with small numbers of skin-emigrant DCs, we propose that this inter-DC antigen transfer functions to amplify presentation across a larger network of lymphoid-resident DCs for efficient T cell activation.