Elevated IL-6 in Midtrimester Amniotic Fluid Is Involved with the Onset of Preeclampsia

PROBLEM: The primary defect of placental development in preeclampsia is speculated to occur at midtrimester gestation. Abnormal feto-maternal immune reactions have been considered as factors in such defective placentation. METHOD OF STUDY: Midtrimester amniotic fluid specimens were retrospectively identified as coming from gestations that later had severe preeclampsia develop, gestations with normal outcomes, and gestations measured for cytokines tumor necrosis factor-α (TNF-α), interleukin (IL-1β, IL-6, and IL-8). The effect of each cytokine on thrombomodulin levels was tested in cultured trophoblast cells. RESULTS: Among the measured cytokines, IL-6 and IL-8 were significantly elevated in the midtrimester amniotic fluid of the future preeclamptic group. Trophoblasts stimulated with TNF-α plus IL-6 had significantly decreased levels of cellular thrombomodulin compared to those without cytokine addition. CONCLUSIONS: Elevated cytokines in midtrimester amniotic fluid suggest an abnormal fetomaternal immune response occurring before the clinical manifestation of preeclampsia. Cytokine-induced suppression of thrombomodulin in trophoblasts may be directly involved in the pathogenesis of preeclampsia.