The Role of Macrophages in Promoting and Maintaining Homeostasis at the Fetal–Maternal Interface

A successful pregnancy requires that the maternal immune system adapts properly to avoid rejection of the semi-allogeneic fetus without compromising the ability to protect the mother and the fetus against infections. In this review, we describe the role of decidual macrophages in creating a homeostatic environment at the fetal-maternal interface. We also discuss their role in pregnancy complications as well as future possibilities to modulate macrophage function therapeutically. Decidual macrophages are enriched at the fetal-maternal interface and play a major role in the regulation of inflammatory responses and the maintenance of a tolerant environment. Their function is, however, not restricted to immune tolerance, but extends to include functions such as the recognition and clearance of infections, the clearance of apoptotic debris, and tissue remodeling. Decidual macrophages seem to largely function as tissue-resident macrophages that are crucial for maintaining homeostasis and reproductive success.