Influence of Animal Genotype and Age on the Amount of Circulating Interferon Induced by Newcastle Disease Virus

Following the paper by Baron & Buckler (1963) describing the release of interferon (Isaacs & Lindenmann, 1957) into the blood of mice injected with viruses, extensive use has been made of this experimental procedure to study various aspects of interferon synthesis in vivo. The usual criterion for selecting animals for such experiments has been to use those within a narrow weight range in random-bred strains. During an investigation on the effect of carcinogens on interferon synthesis in mice (De Maeyer & De Maeyer-Guignard, 1967) we noticed that the amounts of circulating interferon in animals injected with Newcastle disease virus varied with animal age and strain. This observation led to more systematic experiments which are reported here.

Mice belonged to three strains. C3H/He and C57Bl mice were purchased from the Laboratory Animal Centre (M.R.C., Carshalton, Surrey, England). Only the first and second generations derived from the Carshalton breeder mice were studied.