IFN-γ Enhances Production of IFN-α in Human Macrophages but Not in Monocytes

Monocytes/macrophages are efficient producers of alpha interferons (IFN), and IFN-γ is a potent activator of these cells. The present study sought to investigate whether IFN-α affects the capacity of human monocytes/macrophages to produce IFN-α on induction with Sendai virus. Plastic-adherent human peripheral blood monocytes were grown in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) for 3 weeks during which they were transformed into macrophages. At various times, the cultures were pretreated for 24 h with IFN-γ and induced with Sendai virus for IFN-α production. Pretreatment with IFN-γ had no effect on the production of IFN-α during the first days in culture. The production of IFN-α was thereafter significantly enhanced by the IFN-γ pretreatment. Minute amounts of IFN-γ, < 0.1 IU/ml, increased the production of IFN-α in macrophages cultured for more than 7 days. The cooperation between IFN-γ and IFN-α in macrophages may play a role in the antiviral defense of the body.