T-cell suppressor factors play an integral role in preventing fetal rejection.

In previous studies we showed that the blocking of T-cell suppressor factors (TsF) with monoclonal antibody could completely ablate pregnancy, and demonstrated the presence of TsF in fetal and maternal tissues. In our current study we used a monoclonal antibody specific for TsF to determine the time during gestation when TsF is most integral in the maintenance of pregnancy. Significant decreases in the number of viable pregnancies when monoclonal antibody was administered on days 3, 4 and 5 were demonstrated. In addition, ELISAs were used to measure the levels of TsF in tissues from pregnant and non-pregnant mice. Increased levels of TsF in the uterus and the lymph nodes draining the uterus were observed when compared to the same tissues of non-pregnant animals. These data strengthen the hypothesis that TsF is in part responsible for the fetal specific immune supression during pregnancy in allogeneic mice and more clearly define the importance of TsF in the implantation of the embryo.