title: Role of interleukin-10 in regulation of T-cell-dependent and T-cell-independent mechanisms of resistance to Toxoplasma gondii.
abstract: Interleukin-10 (IL-10) is a cytokine which can inhibit T-cell and natural killer (NK) cell functions associated with cell-mediated immunity to intracellular infections. The production of IL-10 by mice infected with Toxoplasma gondii has been implicated in the suppression of lymphocyte proliferation observed during acute toxoplasmosis, as well as susceptibility to infection with this parasite. We have used C57BL/6 mice which lack a functional IL-10 gene (IL-10(-/-) mice) to investigate the role of IL-10 in acute toxoplasmosis. Intraperitoneal infection of IL-10(-/-) mice with T. gondii resulted in 100% mortality by day 13, whereas wild-type C57BL/6 (WT) mice survived acute infection. IL-10(-/-) mice infected with T. gondii had significantly higher serum levels of IL-12 and gamma interferon (IFN-gamma) than WT mice. Early mortality of infected IL-10(-/-) mice was prevented by treatment with IL-10 and significantly delayed by neutralizing antibodies to IL-12 and IFN-gamma. Further studies revealed that SCID/IL-10(-/-) mice infected with T. gondii had delayed time to death compared to IL-10(-/-) mice, indicating that lymphocytes contributed to death of IL-10(-/-) mice. In addition, infected SCID/IL-10(-/-) mice survived longer than infected SCID mice. These latter data indicate that in mice lacking lymphocytes, endogenous IL-10 is associated with increased susceptibility to T. gondii. However, the lack of IL-10 does not alter the infection-induced suppression of T cell and NK cell functions. Our experiments reveal that IL-10 is associated with protection or increased susceptibility to infection with T. gondii, depending on whether mice possess lymphocytes, and demonstrate the important roles of IL-12 and IFN-gamma in the early infection-induced mortality observed in the IL-10(-/-) mice.
authors.affiliation: Department of Immunology and Infectious Diseases, Research Institute, Palo Alto Medical Foundation, California 94301, USA.
authors.forename: L E
authors.initials: LE
authors.lastname: Neyer
authors.forename: G
authors.initials: G
authors.lastname: Grunig
authors.forename: M
authors.initials: M
authors.lastname: Fort
authors.forename: J S
authors.initials: JS
authors.lastname: Remington
authors.forename: D
authors.initials: D
authors.lastname: Rennick
authors.forename: C A
authors.initials: CA
authors.lastname: Hunter
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000276:immunology; D002455:Cell Division; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D007113:Immunity, Innate / Q000235:genetics*; D007371:Interferon-gamma / Q000097:blood / Q000276:immunology / Q000378:metabolism; D016753:Interleukin-10 / Q000235:genetics* / Q000276:immunology* / Q000494:pharmacology; D018664:Interleukin-12 / Q000097:blood / Q000276:immunology / Q000378:metabolism; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D016513:Mice, SCID; D009500:Neutralization Tests; D009573:Nitrites / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D014124:Toxoplasmosis, Animal / Q000276:immunology*; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D019138:Antibodies, Blocking; D009573:Nitrites; D016753:Interleukin-10; D018664:Interleukin-12; D019323:omega-N-Methylarginine; D007371:Interferon-gamma