Immunotherapy in Friend Virus Leukemia. I. Prevention of Friend Leukemia in the Offspring of Immunized Mothers

Summary

Inhibition of a primary virus-induced leukemia was demonstrafed in a model system. DBA/2 Friend leukemic cells, which contain a new virus-directed cellular antigen, were used to immunize DBA/2 or DBA/2 hybrid females. The offspring were effectively protected against large doses of Friend virus for at least 3 weeks after birth. The kinetics of the virus-host interaction and the duration of immunity were studied. After 4–6 weeks the acquired resistance began to decrease. In 10-week-old offspring from immunized mothers the resistance was completely lost, but reappeared after another few weeks. Since living Friend leukemia cells were used for immunization of the mother, the late resistance of the offspring may be explained by a transmission of a small amount of virus, to which an active immunity was formed. Accordingly, only the early resistance was seen if the mothers were immunized with formalin-inactivated Friend virus. Newborn, immunologically incompetent mice were thus shown to be passively protected by maternal antibodies for the time needed to develop an active immune response to Friend virus leukemia. Foster-nursing experiments showed that immunity was transferred mainly by milk and was effective on the first day of suckling. Leukemic mothers did not transfer any immunity. Evaluation of the influence of sex and age showed that young females were more susceptible to Friend virus infection than males of the same strain, and that a natural resistance appeared after the first 3 weeks.