• Mice;
  • maternal influence;
  • foster nursing;
  • allotypes;
  • milk lymphocytes;
  • immunoglobulins

ABSTRACT: Maternal IgG persists longer in young mice (10–12 weeks) than would be predicted from the known half-life of passively administered immunoglobulins. By monitoring maternal and infant allotypes independently, in foster-nursing experiments, we investigated the potential participation of milk lymphocytes in this phenomenon.

When milk cells were experimentally excluded, maternal allotype vanished three weeks earlier than in controls. On the other hand, it was not possible to prolong survival of maternal IgG beyond nine weeks by weekly administration of foster-strain cells or serum; final rejection is in this case preceded by a burst in endogenous IgG production.

Maternal influence initially depresses endogenous IgG production, even in normal F1 offspring. Typical for fostered offspring, which initially have lower levels of endogenous IgG than normal controls, is a burst in production at the age of 6–7 weeks; we speculate that final rejection of transplanted milk lymphocytes may take place concomitant with maturation of the infant's immune system.