The Roles of Uterine Natural Killer (NK) Cells and KIR/HLA-C Combination in the Development of Preeclampsia: A Systematic Review

Figure 1

Preeclampsia (PE) is related to the poor placentation in the early pregnancy. In normal early pregnancy (left picture), extravillous trophoblast cells (EVT) invade deeply enough in the myometrium and also migrate into the endothelium of maternal spiral arteries. This ensures that there is abundant blood flow at the maternal fetal interface. However, in PE patients (right picture), the depth of trophoblast invasion is decreased with insufficient remodeling of trophoblast cells. Blood flow is also reduced in PE. Inappropriate combination of KIR/HLA-C in PE will inhibit the functions of NK cells including secreting angiogenic cytokines. As a result, uterine NK (uNK) cells in these women have low functional activity and they do not support placental growth as needed.