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 nor mal gestation. STUDY DESIGN: A monoclonal antibody raised against human perforin teas used to detect perforin expression in mononuclear cells in first-trimester abor tion, second-trimester preterm labor due to cervical incompetence and term placentas obtained after normal delivery. Fresh frozen tissue sections cont aining 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 of chorionic villi of term placenta, while most were found in decidua and coa gulated blood in maternal vessels and intervillous spaces. The majority of these lymphocytes were CD3-, CD2+ and CD56+. Quantitative comparison of dec idual perforin-positive lymphocytes demonstrated a relative increase in the se lymphocytes in decidua of second-trimester and term placentas. CONCLUSION: The presence of perforin-positive cytotoxic lymphocytes in mate rnal blood and decidua during gestation suggests their roles in pregnancy.