Augmentation of release of cytotoxin from murine bone marrow macrophages by gamma-interferon.

gamma-Interferon (IFN-gamma) was shown to amplify cytotoxin release from murine bone marrow-adherent macrophages in response to an animal lectin as a second stimulus. This stimulation of cytotoxin release was demonstrated both in vitro and in vivo and was maximal 2 h after treatment with IFN-gamma. No change in expression of surface antigens was detected on bone marrow-adherent cells treated with IFN-gamma. IFN-gamma also augmented production of cytotoxin from bone marrow-adherent cells that had been cultured for several days. This cytotoxin was inhibited by rabbit anti-tumor necrosis factor serum and had a molecular weight of 70,000. These findings showed that both freshly isolated and cultured bone marrow macrophages could release cytotoxin and that cytotoxin production in response to a second stimulus was augmented by IFN-gamma. The results also suggest that IFN-gamma can activate all macrophages in vivo, irrespective of their states of maturation and differentiation.