title: Multiple T cell subsets control Francisella tularensis LVS intracellular growth without stimulation through macrophage interferon gamma receptors.
abstract: A variety of data suggest that in vivo production of interferon (IFN)-gamma is necessary, but not sufficient, for expression of secondary protective immunity against intracellular pathogens. To discover specific IFN-gamma-independent T cell mediated mechanisms, we took advantage of an in vitro culture system that models in vivo immune responses to the intracellular bacterium Francisella tularensis live vaccine strain (LVS). LVS-immune lymphocytes specifically controlled 99% of the growth of LVS in wild-type murine bone marrow-derived macrophages. Surprisingly, LVS-immune lymphocytes also inhibited LVS intracellular growth by as much as 95% in macrophages derived from IFN-gamma receptor knockout (IFNgammaR KO) mice. CD8+ T cells, and to a lesser degree CD4+ T cells, controlled LVS intracellular growth in both wild-type and IFNgammaR KO macrophages. Further, a unique population of Thy1+alphabeta+CD4-CD8- cells that was previously suggested to operate during secondary immunity to LVS in vivo strongly controlled LVS intracellular growth in vitro. A large proportion of the inhibition of LVS intracellular growth in IFNgammaR KO macrophages by all three T cell subsets could be attributed to tumor necrosis factor (TNF) alpha. Thus, T cell mechanisms exist that control LVS intracellular growth without acting through the IFN-gamma receptor; such control is due in large part to TNF-alpha, and is partially mediated by a unique double negative T cell subpopulation.
authors.affiliation: Division of Bacterial, Parasitic, and Allergenic Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, MD 20852, USA. cowley@cber.fda.gov
authors.forename: Siobhán C
authors.initials: SC
authors.lastname: Cowley
authors.forename: Karen L
authors.initials: KL
authors.lastname: Elkins
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D005604:Francisella tularensis / Q000254:growth & development* / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000378:metabolism; D017471:Receptors, Interferon / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D013154:Spleen / Q000166:cytology; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism; D014406:Tularemia; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D000096743:Interferon gamma Receptor
chemical_list: D016207:Cytokines; D007371:Interferon-gamma; D009569:Nitric Oxide; D017471:Receptors, Interferon; D014409:Tumor Necrosis Factor-alpha; D000096743:Interferon gamma Receptor