Interferon γ upregulates its own gene expression in mouse peritoneal macrophages

Abstract

Interferon γ (IFN-γ) exerts a variety of immunoregulatory effects on several cell targets. It is generally assumed that IFN-γ is specifically produced by T and large granular lymphocytes. In this study, we show that IFN-γ is constitutively expressed in resting mouse peritoneal macrophages (PM). Treatment of PM with cycloheximide results in a significant accumulation of IFN-γ mRNA, suggesting that a short-lived IFN-γ mRNA accumulates when protein synthesis is inhibited. Moreover, treatment of PM with IFN-γ also results in a clear-cut accumulation of this mRNA. This effect is not observed in murine lymphocytes from mesenteric lymph nodes (which instead produce IFN-γ after phytohemagglutinin treatment) and in mouse cell lines. The treatment of PM with IFN-γ also results in secretion of IFN-γ after 24-48 h. The upregulation of IFN-γ expression is also found in PM from anti-asialo GM1-treated nude mice. We suggest that the ability of PM to produce this IFN-γ is indicative of an autocrine mechanism. The macrophage IFN-γ may play a role in the regulation of cell differentiation and immune response.