Enhancement of Interferon-mediated Protein Kinase in Mouse and Human Plasma in Response to Treatment with Polyadenylic–Polyuridylic Acid (Poly A:Poly U)

Interferon-treated mouse and human cells show enhanced levels of kinase activity manifested by the phosphorylation of endogenous 67,000 (p67K kinase) and 72,000 (p72K kinase) molecular weight proteins, respectively. Both the p67K kinase and the p72K activities are detectable in mouse and human plasma. We have previously shown that the p67K kinase in the plasma of mice may serve as a marker for the presence and action of interferon. Here we show that these kinase activities are enhanced in mice and in patients treated with polyadenylic–polyuridylic acid (Poly A:Poly U) at doses (0.4–0.6 mg/kg body weight) which do not lead to detectable amount of circulating interferon. Mice injected with higher doses of Poly A:Poly U (2–10 mg/kg body weight) show detectable levels of circulating interferon in addition to enhanced levels of p67K kinase in their plasma. Interferon produced under these conditions is acid stable.