Stimulation of Macrophage Synthesis of Complement Clq by Interferon-γ Mediated by Endogenous Interferon-α/β

Abstract

Both exogenous interferon-γ (IFN-γ) and interferon-α/β (IFN-α/β) stimulate Clq mRNA synthesis in murine macrophages. Previous studies suggested that IFN-γ induced endogenous synthesis of IFN-α/β by murine macrophages. In the present study, we determined the indirect effect of IFN-γ on macrophage synthesis of Clq mRNA mediated by endogenous IFN-α/β production. Upregulation of macrophage synthesis of Clq mRNA by both IFN-γ and IFN-α/β was reversed by neutralizing antibody to IFN-α/β but not by nonimmune control serum. IFN-γ was confirmed by ELISA to stimulate a six- to eightfold increase in macrophage secretion of IFNα/β compared with untreated control cells. We tentatively conclude that IFN-γ stimulates macrophage synthesis and secretion of IFN-α/β, which in turn promotes Clq mRNA synthesis in an autocrine or paracrine manner. Thus, exogenous IFN-γ, derived from activated T lymphocytes, may act primarily on the macrophage to stimulate the endogenous synthesis of IFN-α/β for autocrine modulation of a variety of biologic functions, including Clq synthesis.