Regulatory T-Cells in Pregnancy: Historical Perspective, State of the Art, and Burning Questions

In this review, we first revisit the original concept of “suppressor T-cells” in pregnancy, put it in a historical perspective, and then highlight the main data that licensed its resurrection and revision into the concept of “regulatory T-cells” (Tregs) in pregnancy. We review the evidence for a major role of Tregs in murine and human pregnancy and discuss Treg interactions with dendritic and uterine natural killer cells, other players of maternal–fetal tolerance. Finally, we highlight what we consider as the most important questions in the field.