Perinatal viral carcinogenesis: the role of immunity.

The perinatal period cumulates conditions favorable to carcinogenesis that comprise high cellular multiplication rates, unstable homeostasis, and immune incompetence. The placenta allows the passage of various antigens including oncogenic viruses that have immunogenic or tolerogenic effects on the fetus. According to the structural type in different species, the placenta also transfers a diversity of maternal antibodies that protect efficiently the unborn progeny. However, in the postnatal period, the infant deprived of maternal antibodies and still incompetent to produce sufficient levels of immunoglobulins is highly susceptible to viral carcinogenesis. In an experimental system, newborn rats were totally protected against viral leukemogenesis by prenatal immunization of mothers with either live or inactivated leukemia virus. The routes of transfer and the comparative efficiency of serum and milk immunoglobulins of different classes to neutralize the virus were examined. The passage of antibodies under conditions of maternal immunosuppression was also studied.