Placental Immune Defences – Protection against Rejection and Infection

Abstract

The placenta is well recognised for its role as the gateway for provision of nutrients to and removal of waste products from the foetus. The placenta also needs to protect the foetus from maternal immunological attack and provide it with rudimentary immune defence mechanisms through the passage of maternally derived immunoglobulin G in particular. There are multiple cellular and soluble mechanisms that have evolved to prevent rejection of the foetal semi‐allograft by the mother's immune system. These mechanisms also contribute to key physiological processes within the placenta, mother and foetus to ensure pregnancy success. Poor development of the placenta is associated with adverse pregnancy outcomes such as miscarriage and preeclampsia. The placenta is also recognised increasingly for its role in determining longer‐term health of the offspring. Key Concepts Placental development is tightly regulated and leads to a highly structured organ that supports the growth and development of the foetus. Numerous cellular and soluble mechanisms control the maternal immune response to the foetal semi‐allograft. The placenta enables immune defence of the immunologically immature foetus that persists for some months after the baby is born. Perturbations of placental development are associated with early pregnancy loss or later adverse pregnancy outcomes. The placenta is central to the developmental origins of health and disease that determine lifelong health of the offspring.