The interferon-induced hyporesponsive state in variant and parental L cells: a requirement for cell division

L cells grown for 18 to 22 months in the presence of interferon (IFN) retained their sensitivity to the antiviral effect of IFN but were less sensitive to cell growth inhibition by IFN. Moreover, the parental and variant lines became hyporesponsive (i.e. less responsive to virus induction of IFN) with different kinetics after IFN treatment. Experiments using mitomycin C to inhibit cell division suggested that cell division is required to enter the hyporesponsive state.