Assay of an interferon-induced enzyme in white blood cells as a diagnostic aid in viral diseases.

Interferon is part of the system of defence against viral infections and has important cell-regulatory and immunoregulatory functions. It is, however, not always possible to quantify circulating interferon in patients. An assay has been developed to measure an interferon-induced enzyme in white blood cells. The activity of this enzyme is constant in healthy subjects but increases by 2-10 times in 85% of patients with acute viral infections. It is also enhanced in autoimmune diseases and in virus-related malignancies and neurological disorders. The enzyme level was not raised in bacterial infections or non-infectious diseases studied. This simple and rapid biochemical assay of the interferon system could be used for diagnosis and evaluation of many diseases.