Maternal antigenic stimulation actively produces suppressor activity in offspring.

Pregnant B10.A(3R) and B10.A(5R) mice were immunized with heterologous erythrocyte and protein antigens and the active immune responsiveness of their offspring was investigated by the plaque-forming cell (PFC) assay. In offspring derived from mothers which were stimulated with optimal amounts of antigens and which had fully developed antibody-forming cells, there was a clear-cut suppression in development of specific PFC over a significant period after delivery. In order to characterize the suppressor cell population, spleen cells were prepared from offspring whose mothers were immunized and thereafter treated by anti I-Jk or anti I-Jb monoclonal antibody and complement (C') followed by adoptive transfer to normal corresponding mouse strain. Only the group that received 3R spleen cells treated with anti I-Jb monoclonal antibody and C' had no suppressed PFC. To clarify the suppressor site in offspring, precursor B-cells of experimental offspring responded as hapten specific antibody forming cells by employing homologous hapten and heterologous carrier antigens. These results suggest mechanisms for suppression in offspring whose mothers were stimulated during pregnancy.