Innate and Adaptive Immune Systems in Physiological and Pathological Pregnancy

Simple Summary Pregnancy is a continually evolving process with many moving parts that must be tightly regulated on both the maternal and fetal sides to ensure its success. A significant component that must be appropriately regulated is the immune system, which is both an innate and adaptive key player at every stage of pregnancy. Pregnancy plays a unique role in the health outcomes of mothers and neonates later in life. Thus, there is a significant clinical and scientific need to understand the changes in innate and adaptive immune systems in physiological and pathological pregnancy to understand how these systems might be dysregulated in complications such as preterm birth, preeclampsia, and recurrent spontaneous abortions. This review will provide a comprehensive understanding of implicated immune cells and their intricate network of interactions in both normal and complicated pregnancies and highlight some challenges and outstanding questions that need further investigation. The dynamic immunological changes occurring throughout pregnancy are well-orchestrated and important for the success of the pregnancy. One of the key immune adaptations is the maternal immune tolerance towards the semi-allogeneic fetus. In this review, we provide a comprehensive overview of what is known about the innate and adaptive immunological changes in pregnancy and the role(s) of specific immune cells during physiological and pathological pregnancy. Alongside this, we provided details of remaining questions and challenges, as well as future perspectives for this growing field of research. Understanding the immunological changes that occur can inform potential strategies on treatments for the optimal health of the neonate and pregnant individual both during and after pregnancy.