Serum interferon level and (2'-5')oligoadenylate synthetase activity in lymphocytes during clinical interferon application.

Determinations of (2'-5')oligoadenylate synthetase (OAS) in extracts of peripheral mononuclear cells were used to monitor clinical treatment by human leukocyte-derived alpha-interferon (IFN-alpha). The maximum activity of this enzyme was detected about 6 h after the maximum IFN activity in the patient's serum, its half-life being severalfold longer than that of circulating IFN. Thus, even some days after its clearance, IFN can be detected by means of this enzyme. Sixfold increases of the IFN dose were not able to further increase OAS activity induced by doses of about 5 X 10(4) units/kg body weight in adult persons. Intravenous administration of IFN seems not to be superior to its i.m. injection.