Salmonella Enterica serovar Typhimurium induces rapid migration of dendritic cells into the gut lumen

Dendritic cells (DC)s are key elements for the immune responses and can operate as antigen sampling cells. We report now that they can also migrate into the gut lumen upon bacterial challenge. Isolated intestinal loops in BALB/c mice, C57/BL6 and C57/BL6 MyD88 knock out (KO) mice were infected with non invasive GFP-labelled S. Typhimurium strain SL1344 (?SPI1, rpsM-gfp), a derivative of the same strain lacking SPI1 and both fliC and fljB flagellin encoding genes, E. coli DH5a (/pZEP16, rpsM-gfp), or PBS. After three hours, luminal content was harvested, washed and DCs were separated. FACS was carried out to characterize and enumerate the recovered cells. Confocal microscopy (CM) and TEM were also performed. Approximately 7 x 104 cells were present in loops treated with flagellated S. typhimurium SL1344, but not in loops belonging to the C57/BL6 MyD88 KO mice. Phenotypic analysis showed the presence of CD11c+, CX3CR1+, MHCII+, CD8a– and CD11b– cells associated with Salmonella. CM confirmed the increase of CD11c+ DCs in the gut lamina propria. TEM and CM showed bacteria associated with luminal DCs. These data show that Salmonella induces flagellin- and Toll-like receptor-dependent DC migration into the gut lumen