Problem Natural killer (NK) cells are the most abundant lymphocyte population at the maternal–fetal interface. They are suggested to be important during placentation by controlling trophoblast invasion. If placentation is suboptimal, pre-eclampsia can occur.
Method of study Decidual NK (dNK) cells were examined at delivery in 46 women, 22 pre-eclamptic women and 24 healthy controls, by staining for CD56 and CD94 with immunohistochemistry (IHC). Furthermore, we investigated the placental expression and the serum levels of the NK-cell activating cytokines interleukin(IL)-12, IL-15, IL-18 and the anti-inflammatory cytokine IL-10 by IHC and enzyme-linked immunosorbent assay (ELISA), respectively.
Results Pre-eclamptic women had higher number of CD56+ and CD94+ cells in the decidua, indicating an altered receptor expression of dNK cells. We also demonstrate for the first time that the villous trophoblasts show strong immunostaining for IL-12 in placentae from healthy controls, while women suffering from pre-eclampsia have significantly less IL-12. However, pre-eclamptic women had significantly elevated IL-12 and IL-15 levels in serum.
Conclusion Results show increased numbers and altered phenotype of dNK cells in pre-eclampsia, supporting the importance of these cells for a healthy pregnancy. The altered receptor expression of dNK cells together with diminished placental IL-12 expression could implicate an altered NK cell-regulation in pre-eclampsia.