title: Role of endogenous IFN-gamma in macrophage programming induced by IL-12 and IL-18.
abstract: Besides the established role of interleukin-12 (IL-12) and IL-18 on interferon-gamma (IFN-gamma) production by natural killer (NK), T, and B cells, the effects of these cytokines on macrophages are largely unknown. Here, we investigated the role of IL-12/IL-18 on nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) production by CD11b(+) adherent peritoneal cells, focusing on the involvement of endogenously produced IFN-gamma. C57BL/6 cells released substantial amounts of NO when stimulated with IFN-gamma or lipopolysaccharide (LPS), but failed to respond to IL-12 or IL-18 or both. However, IL-12/IL-18 pretreatment was able to program these cells to release 6-8-fold more NO and TNF-alpha in response to LPS or Trypanosoma cruzi stimulation, with NO levels directly correlating with macrophage resistance to intracellular parasite growth. Analysis of IL-12/IL-18-primed cells from mice deficient in IFN-gamma, IFNGR, and IFN regulatory factor-1 (IRF-1) revealed that these molecules were essential for LPS-induced NO release, but TNF-alpha production was IFN-gamma independent. Conversely, the myeloid differentiation factor 88 (MyD88)-dependent pathway was indispensable for IL-12/IL-18-programmed LPS-induced TNF-alpha production, but not for NO release. Contaminant T and NK cells largely modulated the IL-12/IL-18 programming of LPS-induced NO response through IFN-gamma secretion. Nevertheless, a small population of IFN-gamma(+) cells with a macrophage phenotype was also identified, particularly in the peritoneum of chronically T. cruzi-infected mice, reinforcing the notion that macrophages can be an alternative source of IFN-gamma. Taken together, our data contribute to elucidate the molecular basis of the IL-12/IL-18 autocrine pathway of macrophage activation, showing that endogenous IFN-gamma plays an important role in programming the NO response, whereas the TNF-alpha response occurs through an IFN-gamma-independent pathway.
authors.affiliation: Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, Av. Prof. Lineu Prestes 1730, São Paulo, SP, Brazil, CEP 05508-000. krbastos@usp.br
authors.forename: Karina R B
authors.initials: KR
authors.lastname: Bastos
authors.forename: Renato
authors.initials: R
authors.lastname: Barboza
authors.forename: Luiz
authors.initials: L
authors.lastname: Sardinha
authors.forename: Momtchilo
authors.initials: M
authors.lastname: Russo
authors.forename: José M
authors.initials: JM
authors.lastname: Alvarez
authors.forename: Maria Regina D'Império
authors.initials: MR
authors.lastname: Lima
mesh_terms: D000818:Animals; D039481:CD11b Antigen / Q000276:immunology; D004357:Drug Synergism; D050856:Interferon Regulatory Factor-1 / Q000502:physiology; D007371:Interferon-gamma / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D018664:Interleukin-12 / Q000494:pharmacology*; D020382:Interleukin-18 / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism* / Q000469:parasitology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D011994:Recombinant Proteins; D014349:Trypanosoma cruzi / Q000276:immunology / Q000469:parasitology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D039481:CD11b Antigen; D050856:Interferon Regulatory Factor-1; D020382:Interleukin-18; D008070:Lipopolysaccharides; D053594:Myeloid Differentiation Factor 88; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D018664:Interleukin-12; D009569:Nitric Oxide; D007371:Interferon-gamma