Production of Immune Interferon (Type II) in Cocultures of Mouse Peritoneal Macrophages and Syngeneic Tumour Cells

Mouse peritoneal macrophages were activated by coculture with syngeneic methylcholanthrene-induced sarcoma cells [7], which grow as an ascites tumour in C3D2 mice [3]. During 4-5 days of cocultivation tumour cells progressively died, leaving highly activated macrophages. Cell-free supernatant harvested from the cultures contained larger amounts of interferon than either macrophages or tumour cells cultivated alone. Peak activity of interferon occurred on day 2. Non-adherent cells cultivated together with tumour cells did not produce interferon. Removal of all non-adherent cells from macrophage cultures and host cells from tumour cell suspension did not abolish interferon production. The macrophages thus seem to be the interferon-producing cells, but the possibility that the very few remaining lymphocytes may cooperate with the macrophages in interferon production cannot be totally ruled out. The interferon produced could not be inactivated by antibodies against virus-induced interferon and was destroyed by treatment at pH 2, indicating that the interferon was not of the alpha or beta type.