The interferon system in subacute sclerosing panencephalitis and its response to isoprinosine.

Plasma interferon activity (IFN) and its spontaneous and stimulated production by peripheral blood mononuclear cells (PBMC) was studied in 11 patients with subacute sclerosing panencephalitis (SSPE) and age-matched healthy controls. The patients, similar to the healthy controls, had no detectable plasma IFN activity. However, their PBMC failed to produce IFN in response to stimulation with poly I:C and PHA. After isoprinosine administration to 7 patients for several days a significant increase in plasma IFN activity was observed and their PBMC responded to stimulation by producing IFN. The long-term effect of isoprinosine on the IFN response was evaluated in 3 patients who had been treated for 57-88 days. Induction of the abolished IFN production was observed with initiation of therapy. However, discontinuation of isoprinosine for 10 days resulted in recurrence of the inactivation state of the IFN system.