title: Bystander activation of CD8+ T cells contributes to the rapid production of IFN-gamma in response to bacterial pathogens.
abstract: The bacterium Burkholderia pseudomallei causes a life-threatening disease called melioidosis. In vivo experiments in mice have identified that a rapid IFN-gamma response is essential for host survival. To identify the cellular sources of IFN-gamma, spleen cells from uninfected mice were stimulated with B. pseudomallei in vitro and assayed by ELISA and flow cytometry. Costaining for intracellular IFN-gamma vs cell surface markers demonstrated that NK cells and, more surprisingly, CD8(+) T cells were the dominant sources of IFN-gamma. IFN-gamma(+) NK cells were detectable after 5 h and IFN-gamma(+) CD8(+) T cells within 15 h after addition of bacteria. IFN-gamma production by both cell populations was inhibited by coincubation with neutralizing mAb to IL-12 or IL-18, while a mAb to TNF had much less effect. Three-color flow cytometry showed that IFN-gamma-producing CD8(+) T cells were of the CD44(high) phenotype. The preferential activation of NK cells and CD8(+) T cells, rather than CD4(+) T cells, was also observed in response to Listeria monocytogenes or a combination of IL-12 and IL-18 both in vitro and in vivo. This rapid mechanism of CD8(+) T cell activation may be an important component of innate immunity to intracellular pathogens.
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: G
authors.initials: G
authors.lastname: Lertmemongkolchai
authors.forename: G
authors.initials: G
authors.lastname: Cai
authors.forename: C A
authors.initials: CA
authors.lastname: Hunter
authors.forename: G J
authors.initials: GJ
authors.lastname: Bancroft
mesh_terms: D000818:Animals; D016957:Burkholderia pseudomallei / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D002478:Cells, Cultured; D005260:Female; D007156:Immunologic Memory; D007369:Interferon Inducers / Q000494:pharmacology; D007371:Interferon-gamma / Q000096:biosynthesis*; D018664:Interleukin-12 / Q000502:physiology; D020382:Interleukin-18 / Q000502:physiology; D007399:Interphase / Q000276:immunology; D007424:Intracellular Fluid / Q000276:immunology / Q000382:microbiology; D007694:Killer Cells, Natural / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D007700:Kinetics; D008088:Listeriosis / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology
chemical_list: D007369:Interferon Inducers; D020382:Interleukin-18; D014409:Tumor Necrosis Factor-alpha; D018664:Interleukin-12; D007371:Interferon-gamma