An inhibitor of interferon action: I. Physical association of the inhibitor with interferon-gamma.

Previously, an inhibitor of interferon action has been identified in mouse lymphokine preparations. The inhibitor was produced following IFN-gamma production and thus may be involved in regulation of IFN-gamma action. We now show that native inhibitor activity as isolated from crude and partially purified IFN-gamma preparations migrates along with interferon activity on molecular sieving gels. IFN-gamma which comigrates with inhibitor migrates at a slightly higher molecular weight than IFN-gamma free of inhibitor. This inhibitor activity correlates with the decreased antiviral activity of crude IFN-gamma produced late in the course of mitogen stimulation. This is apparent for both plaque reduction and yield reduction assays for interferon. This association of IFN-gamma with its inhibitor suggests a mechanism for the local regulation of IFN-gamma activity.