title: Role of IL-6 in activation of T cells for acquired cellular resistance to Listeria monocytogenes.
abstract: We have previously shown that IL-6 is a major cytokine in the serum of mice infected with the intracellular bacterium Listeria monocytogenes, and that injection of rIL-6 before, but not after, infection promotes the recovery of mice from listeriosis. Here we demonstrate that IL-6 is required in the early stages of infection, in that injection of anti-IL-6 Ab 24 or 4 h before infection, but not 24 h after, led to a massive increase in bacterial numbers 4 or more days after infection. On the other hand, injection of rIL-6 before infection significantly suppressed bacterial numbers in the liver and spleen 3 to 4 days after infection and increased the production of IFN-gamma by in vitro cultured CD4+ and CD8+ T cells in response to specific Ag. rIL-6 did not protect SCID mice, which lack both T and B lymphocytes, against Listeria infection. The protective effect of rIL-6 was neutralized by the injection of Ab to IFN-gamma. We conclude that IL-6 plays an essential role in the activation of T cells to produce IFN-gamma, the cytokine that is central to acquired cellular resistance to intracellular bacteria.
authors.affiliation: Department of Microbiology, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
authors.forename: R J
authors.initials: RJ
authors.lastname: Simpson
authors.forename: C
authors.initials: C
authors.lastname: Cheers
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D005260:Female; D007371:Interferon-gamma / Q000502:physiology; D015847:Interleukin-4 / Q000096:biosynthesis; D015850:Interleukin-6 / Q000494:pharmacology*; D008089:Listeria monocytogenes / Q000276:immunology*; D008088:Listeriosis / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D011994:Recombinant Proteins / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D015850:Interleukin-6; D011994:Recombinant Proteins; D015847:Interleukin-4; D007371:Interferon-gamma