Perforin-positive cytotoxic lymphocytes in pregnancy.

OBJECTIVE: To investigate whether perforin-positive, cytotoxic lymphocytes are present in the first and second trimester as well as at term during normal gestation. STUDY DESIGN: A monoclonal antibody raised against human perforin was used to detect perforin expression in mononuclear cells in first-trimester abortion, second-trimester preterm labor due to cervical incompetence and term placentas obtained after normal delivery Fresh frozen tissue sections containing first- and second-trimester decidua and placental tissues as well as decidua of maternal and fetal surfaces of term placenta were stained using an immunoperoxidase method. RESULTS: Occasional perforin-positive lymphocytes were present in stroma ofchorionic villi of term placenta, while most were found in decidua and coagulated blood in maternal vessels and intervillous spaces. The majority of these lymphocytes were CD3-, CD2+ and CD56+. Quantitative comparison of decidual perforin-positive lymphocytes demonstrated a relative increase in these lymphocytes in decidua of second-trimester and term placentas. CONCLUSION: The presence of perforin-positive cytotoxic lymphocytes in maternal blood and decidua during gestation suggests their roles in pregnancy.