title: Cutting edge: IL-12 is required for the maintenance of IFN-gamma production in T cells mediating chronic resistance to the intracellular pathogen, Toxoplasma gondii.
abstract: IL-12 is required for the development of IFN-gamma-dependent resistance to intracellular pathogens but is not thought to play a major role in its maintenance. To directly assess the requirement for continuous IL-12 signaling in long-term cell-mediated immunity, recombinant cytokine was transiently administered to IL-12 p40-deficient mice during the first 2 wk of infection with the intracellular pathogen Toxoplasma gondii. As expected, these animals survived the acute phase and established chronic infections. However, 4-6 wk after IL-12 withdrawal, the mice exhibited increased brain cyst burdens and succumbed to toxoplasmic encephalitis. Reactivation was associated with a loss of T-dependent IFN-gamma production without a concomitant increase in Th2 cytokine expression. Importantly, parasite Ag-induced IFN-gamma synthesis by purified T cells from these animals could be restored by in vitro exposure to IL-12. These results argue that endogenous IL-12 is required for the long-term maintenance of IFN-gamma-dependent resistance against intracellular pathogens.
authors.affiliation: Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: G
authors.initials: G
authors.lastname: Yap
authors.forename: M
authors.initials: M
authors.lastname: Pesin
authors.forename: A
authors.initials: A
authors.lastname: Sher
mesh_terms: D000818:Animals; D002908:Chronic Disease; D016207:Cytokines / Q000096:biosynthesis; D004334:Drug Administration Schedule; D007113:Immunity, Innate; D007274:Injections, Intraperitoneal; D007371:Interferon-gamma / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D018664:Interleukin-12 / Q000008:administration & dosage / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D007424:Intracellular Fluid / Q000276:immunology / Q000469:parasitology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism / Q000469:parasitology; D018418:Th2 Cells / Q000276:immunology / Q000378:metabolism; D014122:Toxoplasma / Q000276:immunology*; D014124:Toxoplasmosis, Animal / Q000276:immunology* / Q000517:prevention & control
chemical_list: D016207:Cytokines; D018664:Interleukin-12; D007371:Interferon-gamma