Enhancing Effect of Interferon Pretreatment on Interferon Production

Abstract

Pretreatment of mouse L cells with interferon (IF) preparations enhanced IF production in response to stimulation with polyinosinic-polycytidylic acid (poly I·poly C). The enhancement of IF production by the pretreatment was maximal with 5 to 10 units/ml of IF. Pretreatment with approximately 1 unit/ml of IF caused no significant enhancement. The enhancement was observed with all IF preparations tested, crude or partially purified, prepared by induction with either poly I·poly C, Escherichia coli endotoxin or Newcastle disease virus. IFs harvested at different times after induction with high and low concentrations of poly I·poly C were equally effective. The enhancing ("priming") activity exhibited "species specificity." However, pretreatment with a high dose of human or rabbit IF, which showed an activity of about 10 units/ml even in the heterologous L cells, enhanced mouse IF production. Studies on physicochemical properties of the active factor indicated that the "priming" activity may be ascribable to IF molecules and not to any other factor in the IF preparations.