Expression of lymphocyte perforin in the mouse uterus during pregnancy

In situ hybridization and immunofluorescence were used to study the expression of a lymphocyte pore-forming protein (perforin) in the uterus of pregnant mice. Cells expressing perforin mRNA were detected as early as gestation day 5, whereas perforin protein was detected one or two days later. Although the number of cells expressing both perforin mRNA and perforin protein varied subsequently with time, they were consistently observed from the day of implantation until parturition. The highest levels of mRNA expression were observed sometime during midgestation. The high abundance of this cytolytic protein in the metrial gland during pregnancy and the time course of its expression thus suggest that GMG perforin expression is tightly regulated, probably hormonally, by the uterus, and that GMG cell perforin plays an important role in the normal completion of pregnancy.