title: Differential susceptibility of activated macrophage cytotoxic effector reactions to the suppressive effects of transforming growth factor-beta 1.
abstract: We examined the effects of TGF-beta 1 on induction of several activated macrophage antimicrobial activities against the protozoan parasite Leishmania, and on induction of tumoricidal activity against the fibrosarcoma tumor target 1023. TGF-beta by itself did not affect the viability of either the intracellular or extracellular target in concentrations up to 200 ng/ml. As little as 1 ng/ml TGF-beta, however, suppressed more than 70% of the intracellular killing activity of macrophages treated with lymphokines. In contrast, more than 100 ng/ml TGF-beta was required to suppress intracellular killing by cells activated with an equivalent amount of recombinant IFN-gamma. Addition of TGF-beta for up to 30 min after exposure to activation factors significantly reduced macrophage killing of intracellular parasites. Pretreatment of macrophages with TGF-beta was even more effective: treatment of cells with TGF-beta for 4 h before addition of activation factors abolished all macrophage intracellular killing activity. Regardless of treatment sequence, however, TGF-beta had absolutely no effect, at any concentration tested, on activated macrophage resistance to infection induced by lymphokines or by the cooperative interaction of IFN-gamma and IL-4. Effects of TGF-beta on tumoricidal activity of activated macrophages was intermediate to that of its effects on intracellular killing or resistance to infection. Lymphokine-induced tumor cytotoxicity was marginally (25%) affected by TGF-beta; 200 ng/ml was able to suppress IFN-gamma-induced tumoricidal activity by 40%. Thus, TGF-beta dramatically suppressed certain activated macrophage cytotoxic effector reactions, but was only partially or not at all effective against others, even when the same activation agent (IFN-gamma) was used. The biochemical target for TGF-beta suppressive activity in these reactions may be the pathway for nitric oxide production from L-arginine, because TGF-beta also inhibited the generation of nitric oxide by cytokine-activated macrophages.
authors.affiliation: Department of Cellular Immunology, Walter Reed Army Institute of Research, Washington, DC 20307-5100.
authors.forename: B J
authors.initials: BJ
authors.lastname: Nelson
authors.forename: P
authors.initials: P
authors.lastname: Ralph
authors.forename: S J
authors.initials: SJ
authors.lastname: Green
authors.forename: C A
authors.initials: CA
authors.lastname: Nacy
mesh_terms: D000818:Animals; D003470:Culture Media; D003602:Cytotoxicity, Immunologic; D005354:Fibrosarcoma / Q000276:immunology; D007371:Interferon-gamma / Q000502:physiology; D007700:Kinetics; D007895:Leishmania tropica / Q000276:immunology*; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D013491:Suppressor Factors, Immunologic; D013601:T-Lymphocytes / Q000276:immunology; D016212:Transforming Growth Factor beta / Q000502:physiology*; D014407:Tumor Cells, Cultured
chemical_list: D003470:Culture Media; D013491:Suppressor Factors, Immunologic; D016212:Transforming Growth Factor beta; D007371:Interferon-gamma