NK cells and pre-eclampsia.

Pre-eclampsia, a disease of pregnancy, is a cause of maternal and fetal mortality worldwide and a major factor in preterm birth. Up to 10% of primipara suffer from this disorder, characterized by pregnancy-induced hypertension and proteinuria, usually in the third trimester when fetal demands on the placenta are greatly increased. The disease is thought to stem from an insufficiency in utero-placental blood flow triggering a cascade of events leading to the maternal syndrome, which may have been initiated by defective placentation early in pregnancy. Theories abound as to the primary cause of the placental pathologies associated with the disease, including those based on maternal immunity and the unique immune environment of the placental bed. Accumulating evidence from animal models, genetic studies, and isolated decidual leukocytes suggests that decidual natural killer (NK) cells supply factors necessary for development and arterial modification of the maternal-fetal interface. This beneficial role of NK cells to normal placentation may shed light on the cause of the placental pathologies observed in pre-eclampsia.