title: Salmonella flagellin induces bystander activation of splenic dendritic cells and hinders bacterial replication in vivo.
abstract: Bacterial flagellin is a target of innate and adaptive immune responses during Salmonella infection. Intravenous injection of Salmonella flagellin into C57BL/6 mice induced rapid IL-6 production and increased expression of activation markers by splenic dendritic cells. CD11b(+), CD8alpha(+), and plasmacytoid dendritic cells each increased expression of CD86 and CD40 in response to flagellin stimulation, although CD11b(+) dendritic cells were more sensitive than the other subsets. In addition, flagellin caused the rapid redistribution of dendritic cells from the red pulp and marginal zone of the spleen into the T cell area of the white pulp. Purified splenic dendritic cells did not respond directly to flagellin, indicating that flagellin-mediated activation of splenic dendritic cells occurs via bystander activation. IL-6 production, increased expression of activation markers, and dendritic cell redistribution in the spleen were dependent on MyD88 expression by bone marrow-derived cells. Avoiding this innate immune response to flagellin is important for bacterial survival, because Salmonella-overexpressing recombinant flagellin was highly attenuated in vivo. These data indicate that flagellin-mediated activation of dendritic cells is rapid, mediated by bystander activation, and highly deleterious to bacterial survival.
authors.affiliation: Department of Medicine, Division of Gastroenterology, Hepatology, and Nutrition, McGuire Translational Research Facility, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
authors.forename: Rosa-Maria
authors.initials: RM
authors.lastname: Salazar-Gonzalez
authors.forename: Aparna
authors.initials: A
authors.lastname: Srinivasan
authors.forename: Amanda
authors.initials: A
authors.lastname: Griffin
authors.forename: Guruprasaadh
authors.initials: G
authors.lastname: Muralimohan
authors.forename: James M
authors.initials: JM
authors.lastname: Ertelt
authors.forename: Rajesh
authors.initials: R
authors.lastname: Ravindran
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Vella
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: McSorley
mesh_terms: D000818:Animals; D024201:Bystander Effect / Q000276:immunology*; D039481:CD11b Antigen / Q000378:metabolism; D016827:CD8 Antigens / Q000378:metabolism; D002460:Cell Line; D004261:DNA Replication / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics*; D003713:Dendritic Cells / Q000276:immunology*; D005408:Flagellin / Q000276:immunology*; D015850:Interleukin-6 / Q000097:blood; D051379:Mice; D008810:Mice, Inbred C57BL; D012475:Salmonella / Q000276:immunology*; D012480:Salmonella Infections / Q000276:immunology; D013154:Spleen / Q000276:immunology*
chemical_list: D039481:CD11b Antigen; D016827:CD8 Antigens; C409469:CD8 antigen, alpha chain; D004269:DNA, Bacterial; D015850:Interleukin-6; D005408:Flagellin