The role of decidual immune cells on human pregnancy

- Natural killer cells present in human decidua play an important role in promoting trophoblast invasion and spiral artery remodeling.
- Decidual macrophages and dendritic cells are important for defense against infection and may be critical in both spiral artery remodeling and immunomodulation during pregnancy.
- Foxp3+ regulatory T cells and CD4+HLA-G+ T cells are crucial for ensuring immune tolerance at the maternal-fetal interface.

The maternal-fetal interface undergoes dynamic changes to allow the fetus to grow and develop in the uterus, despite being recognized by the maternal immune cells. Within the innate immune system, decidual natural killer cells and antigen presenting cells (including macrophages and dendritic cells) that comprise a large proportion of the decidual leukocyte populations play an important role in modulating trophoblast invasion, angiogenesis and vascular remodeling. On the other hand, within the adaptive immune system, CD8+ T cells, effector CD4+ T cells, Foxp3+ regulatory T cells and CD4+HLA-G+ suppressor T cells are identified as potential players in maintaining immune tolerance toward the semi-allogeneic fetus. This review discusses how these key immune cells contribute to pregnancy outcome and the complex interactions between the innate and adaptive immune system during human pregnancy.