Systemic induction of interferon in chicks with various NDV strains. I. Relationship between virulence of the virus and the mechanism of interferon production.

Abstract

The ability of NDV strains to induce interferon (IF) in chicks is closely related with their virulence. Virulent strains are more potent inducers than avirulent strains. With the avirulent strains, induction of maximum IF took place uniformly at the 2nd hour, whereas with the virulent strains considerably later, at times depending on the strain. The main source of early IF inducible with the avirulent strains is the spleen. Early IF is extremely sensitive to cortisone, but it is not significantly inhibited by FPA. Pretreatment of chicks with endotoxin brought about a state of tolerance. In contrast, the appearance of late IF is less sensitive to cortisone, it is prevented by FPA, hardly influenced by splenectomy and a tolerance to it can be induced by pretreatment with homologous virus, but can not be induced with endotoxin.