Cross-resistance to Human Interferon-{gamma} of Human Interferon-beta-resistant F-IFr Cells

F-IF^r cells, which are more resistant to the anticellular and antiviral action of human α and interferons (IFN-α and IFN-) than the parental RSa cells, were also found to be more resistant to both the anticellular and antiviral effect of IFN-γ. A high level of 25A synthetase was induced by treatment with IFN-α or -, but induction of 25A synthetase was not detected after IFN-γ treatment of the cells. F-IF^r cells had less than half the number of specific binding sites for IFN-α than the parental RSa cells.