Why the immune system of a pregnant woman does not attack her developing fetus is one of most remarkable features of pregnancy, and several underlying mechanisms have been described. However, Adrian Erlebacher and colleagues, at the New York University School of Medicine, New York, have now identified a new mechanism to explain why the mouse maternal immune system does not attack the fetuses.
Once an embryo implants into the wall of the uterus, a cellular structure known as the decidua forms around the embryo and placenta. In the study, the formation of the decidua was found to prevent immune sentinel cells known as DCs from leaving the maternal/fetal interface and traveling to the local lymph nodes to activate an immune response toward the fetus.
The authors therefore suggest that impaired formation or function of the human decidua might allow DCs to leave the decidua to initiate an aggressive immune response toward the fetus, something that might contribute to poor pregnancy outcomes.
In an accompanying commentary, Bali Pulendran, at Emory Vaccine Center at Yerkes National Primate Research Center, Atlanta, discusses how this new research affects current thinking about avoiding immune surveillance at the maternal/fetal interface.
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