title: Synergism between tumor necrosis factor-alpha and interferon-gamma on macrophage activation for the killing of intracellular Trypanosoma cruzi through a nitric oxide-dependent mechanism.
abstract: Intracellular replication of the protozoan parasite Trypanosoma cruzi inside macrophages is essential for the production of the disease and the development of the parasite. Two CD4+ T cell lines, A10 and A28, were established from T. cruzi-infected BALB/c mice which specifically proliferated to parasite antigens. The trypanocidal activity of BALB/c macrophages was induced upon culture with the A10, but not with the A28 T cell line. The cell-free supernatant from this A10 line, as well as from immune spleen cells stimulated with specific antigen or concanavalin A, but not from the A28 T cell line also activated the trypanocidal activity of peritoneal macrophages or of the J774 macrophage-like cell line. when the lymphokine content of the supernatants from both cell lines was analyzed, it was found that the A10 T cell line secreted interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and interleukin 2, whereas the A28 line did not secrete IFN-gamma upon stimulation. Furthermore, the trypanocidal-inducing ability of A10 supernatant was completely abrogated by neutralizing anti-IFN-gamma antibodies and partially abrogated by neutralizing anti-TNF-alpha antibodies. When recombinant cytokines were added to J774 cells, IFN-gamma was able to induce significant trypanocidal activity whereas TNF-alpha was almost ineffective. However, TNF-alpha or lipopolysaccharide (LPS) showed a synergistic effect with IFN-gamma on macrophage activation. IFN-gamma triggered nitric oxide (NO) synthesis by J774 cells whereas TNF-alpha was almost ineffective. TNF-alpha and LPS were also synergistic with IFN-gamma in the NO production. Both the NO production and the trypanocidal activity in J774 cells induced by T cell supernatants or lymphokine combinations were inhibited by N-monomethyl-L-arginine, a competitive inhibitor of NO synthase activity. A good correlation between the levels of NO production and trypanocidal activity induced by different lymphokine preparations was found. Those results suggest that IFN-gamma and TNF-alpha, secreted by T. cruzi-immune T cells, are involved in the activation of the trypanocidal activity of mouse macrophages through an NO-dependent mechanism.
authors.affiliation: Centro de Biología Molecular, CSIC-UAM Universidad Autónoma de Madrid, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: Muñoz-Fernández
authors.forename: M A
authors.initials: MA
authors.lastname: Fernández
authors.forename: M
authors.initials: M
authors.lastname: Fresno
mesh_terms: D000818:Animals; D014355:Chagas Disease / Q000276:immunology*; D004357:Drug Synergism; D007371:Interferon-gamma / Q000502:physiology*; D008222:Lymphokines / Q000502:physiology; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism*; D010529:Peritoneal Cavity / Q000166:cytology; D013601:T-Lymphocytes / Q000276:immunology; D014349:Trypanosoma cruzi / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
chemical_list: D008222:Lymphokines; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D007371:Interferon-gamma