Temporal changes in dendritic cell subsets, cross-priming and costimulation via CD70 control CD8+ T cell responses to influenza

The question of which dendritic cells (DCs) respond to pulmonary antigens and cross-prime CD8(+) T cells remains controversial. We show here that influenza-specific CD8(+) T cell priming was controlled by different DCs at different times after infection. Whereas early priming was controlled by both CD103(+)CD11b(lo) and CD103-CD11b(hi) DCs, CD103-CD11b(hi) DCs dominated antigen presentation at the peak of infection. Moreover, CD103-CD11b(hi) DCs captured exogenous antigens in the lungs and directly cross-primed CD8(+) T cells in the draining lymph nodes without transferring antigen to CD8(alpha)(+) DCs. Finally, we show that CD103-CD11b(hi) DCs were the only DCs to express CD70 after influenza infection and that CD70 expression on CD103-CD11b(hi) DCs licensed them to expand CD8(+) T cell populations responding to both influenza and exogenous ovalbumin.