Interleukin-6 concentrations in the placenta and blood in normal pregnancies and preeclampsia

Aim: To evaluate whether IL-6 concentrations in the placenta and blood from women with preeclampsia differed from those in normal pregnancies. Methods: This study involved 41 pregnant women carrying single fetuses. Of these pregnancies, 23 were normal pregnant and 18 were preeclamptic patients. The average gestational age at entry was 37-38 weeks of gestation. Blood was collected before the onset of labor. Serum was separated and stored at - 20 degrees C. A tissue segment of the placenta was cut and chilled in liquid nitrogen immediately after delivery and stored at - 80 degrees C. The frozen tissue was added to phosphate-buffered saline and fully homogenized. After centrifugation, the separated supernatant was stored at - 80 degrees C. IL-6 levels in separated serum and IL-6 and total protein (TP) levels in separated supernatant were measured. The presence of IL-6 in the placenta was evaluated by immunohistochemistry in five preeclamptic and five normal pregnant patients. Results: Neither IL-6/TP levels in the placenta nor IL-6 levels in blood differed significantly between the two groups. IL-6 immunostaining on trophoblastic cells in the placenta was weak in one and absent in four in normal pregnancies, and absent in all patients with preeclampsia. There was no strong immunostaining for IL-6 in preeclampsia by immunohistochemistry. Conclusions: Our findings suggest that IL-6 in the placenta and blood does not play a significant role in the induction of an immunologic imbalance, which may contribute to the etiological mechanism leading to preeclampsia.