Regulatory T and T helper 17 cells: Their roles in preeclampsia.

Regulatory T (Treg) cells have been identified as key immune regulators and are important to fetal survival within the maternal uterus. T helper 17 (Th17) cells have also emerged as a new subset of effector helper T cells and play significant roles in host defense against extracellular pathogens, autoimmune conditions, and inflammatory chronic diseases. Recent findings have provided strong support for the contribution of Th17 and Treg cells to successful pregnancy. Disorders of pregnancy such as preeclampsia (PE) and recurrent spontaneous abortion (RSA) are associated with low frequencies of Treg cells and high levels of Th17 cells. Here, we review current knowledge on Tregs and Th17 cells and shed light on their roles in both normal pregnancy and PE. We also discuss the imbalance between Th17 cells and Treg cells which is known as a major contributory factor in the pathophysiology of PE.