Salmonella efficiently enter and survive within cultured CD11c(+) dendritic cells initiating cytokine expression

While Salmonella infects macrophages, this cell population may not be the o nly one important for disseminating intracellular bacteria from mucosal sit es. Dendritic cells (DC) are present in the Peyer's patches and are mobiliz ed following stimulation. Such characteristics would seem to be ideal for t he dissemination of an intracellular, mucosal pathogen. However, it has bee n difficult to obtain sufficient numbers of DC to assess their ability to h arbor Salmonella or to monitor DC in vivo. In the present study, this probl em has been addressed by expanding DC in vivo using flt3 ligand, followed b y the purification of CD11c(+) cells using antibody-coated magnetic beads o r by fluorescence-activated cell sorting. Salmonella dublin were found to b e efficiently internalized, and to survive and replicate within purified CD 11c(+) DC, and also in CD11c(+), CD8 alpha(+) or CD11c(+), CD11b(+) DC subp opulations. The ability of Salmonella to enter DC is of similar magnitude t o that reported for macrophages, suggesting that this cell population could be an important host cell for dissemination of this pathogen from mucosal sites. Furthermore, infected DC responded to Salmonella by secretion of IL- l, IL-6 and IL-12. As such, these cells may be important sources of these c ytokines during the host response against Salmonella infection.