The major interest in materno-foetal relation is why fetus is not rejected by the mother, even in a different genetic background in mother and her husband. But in this article we have been investigating about the effect(s) of maternal antigenic stimulation or infection upon the active immune responses in the offspring. The results of various researchers have certainly proposed significant problems as to the defense of infants against infectious agents, especially those introduced by their mothers. But we have already reported that maternal antigenic stimulation greatly suppresses the specific immune response of the offspring in a system of mouse vs heterologous erythrocytes and other T-dependent antigens. This suppression was antigen specific and effective on 1/6 life of rodents. The mechanisms that concerned in this suppression were not antigen administered nor antibody produced in the mother. The supporting evidences were that this suppression was MHC restricted between mother and her young. The system examined was separating genetic backgrounds that the haplotype was different in F2 family where half of the young were identical but not in remainder to the Fl mother mouse. Moreover, cytokine level in both mother and her young, IFN-γ levels was upregulated in such a young whose mother was immunized with antigen. The significance of this phenomenon was accessed as biological and medical intervention especially for the children health care and prevention of hypersensitivities.