Induction of an inhibitor of interferon action in a mouse lymphokine preparation.

An inhibitor of interferon action was identified in mouse lymphokine preparations. The inhibito was first detected in the supernatant fluid of mouse spleen cells at 72 h after stimulation by staphylococcal enterotoxin A. Inhibitor was not detected in supernatant fluids from unstimulated cultures. This inhibitor blocks the antiviral activity of both immune and fibroblast interferons. The inhibitor was purified 1,000-fold by two-step column chromatography. The partially purified inhibitor blocked the antiviral activity of up to 400 U of interferon. The immunosuppressive effect of interferon was also blocked by the inhibitor, suggesting that the inhibitor may modulate the immunoregulatory function of interferon.