Maternal T cells regulate placental size and fetal survival.

The placental immunotrophism hypothesis states that maternal T cells, through their lymphokines, exert a positive influence on placental growth, which can lead to improved chances of fetal survival. We report here that deleting maternal T cells by monoclonal antibody injection during midgestation is accompanied by increased fetal resorption and decreased placental weight and phagocytosis in two different strain combinations of mice. Conversely, mice with T-cell proliferative disease show increased placental weight and phagocytosis, which can be reversed following T-cell depletion during pregnancy. Furthermore, female mice that are prone to fetal resorption show improved fetal survival if injected with spleen cells from mice with T-cell proliferative disease. These results are in accord with predictions of the placental immunotrophism hypothesis and imply that maternal T cells can participate in the prevention of spontaneous fetal resorption.