Immunologic consequences of vaccination against abortion in mice.

CBA/J female mice have a high rate of fetal resorption when mated with DBA/2J males. This fetal wastage can be dramatically reduced by immunizing the female with BALB/cJ but not DBA/2J spleen cells. We report here that immunization with BALB/cJ (but not DBA/2J) spleen cells leads to 1) anti-paternal MHC antibody that is predominantly of the IgG1 isotype, and which disappears from the serum during pregnancy; 2) increased active suppression in both the spleen and placenta; and 3) an ability to adoptively transfer the fetal protection and placental suppression with serum from the immunized mice. Congenic absorption studies before adoptive transfer indicate that the active component of the serum is also directed against the paternal MHC haplotype. These results indicate that maternal humoral immunity can lead to increased fetal protection in correlation with local active suppression in the placenta. They also suggest an expansion of the placental immunoabsorbent hypothesis to include the induction of active suppression against maternal cell-mediated immunity.