Suppressor cells in the human maternal-fetal relationship.

The mixed lymphocyte culture (MLC) of maternal and newborn (cord) cells is significantly weaker than that of father-newborn and control-newborn cultures. This hyporeactivity was found not to be due to an impaired function or tolerance of either the maternal or neonatal cells. We investigated the possibility that a specific, in vivo-induced suppressor cell was active in the diminished maternal-newborn reaction. Suppressor cells were found to be active in both the stimulating and responding populations in the unidirectional MLC. The removal of TG cells from the responding (maternal or newborn) population resulted in an increase of reactivity specific for the corresponding stimulating population (newborn or maternal). The suppressor activity within the stimulating population was carried out by a radiosensitive cell, which did not require proliferation to exert its effect. We suggest that the observed hyporeactivity of maternal-newborn mixed lymphocyte cultures is due to the modulation of the reaction by specific, in vivo-induced suppressor cells.