CD8α⁺ Dendritic Cells Are an Obligate Cellular Entry Point for Productive Infection by Listeria monocytogenes

CD8α⁺ dendritic cells (DCs) prime cytotoxic T lymphocytes during viral infections and produce interleukin-12 in response to pathogens. Although the loss of CD8α⁺ DCs in Batf3^-/- mice increases their susceptibility to several pathogens, we observed that Batf3^-/- mice exhibited enhanced resistance to the intracellular bacterium Listeria monocytogenes. In wild-type mice, Listeria organisms, initially located in the splenic marginal zone, migrated to the periarteriolar lymphoid sheath (PALS) where they grew exponentially and induced widespread lymphocyte apoptosis. In Batf3^-/- mice, however, Listeria organisms remain trapped in the marginal zone, failed to traffic into the PALS, and were rapidly cleared by phagocytes. In addition, Batf3^-/- mice, which lacked the normal population of hepatic CD103⁺ peripheral DCs, also showed protection from liver infection. These results suggest that Batf3-dependent CD8α⁺ and CD103⁺ DCs provide initial cellular entry points within the reticuloendothelial system by which Listeria establishes productive infection.