Placental Immune Defences – Protection against Rejection and Infection


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.

Keywords: placenta; trophoblast; pregnancy; foetus; immunoglobulin; cytokine; innate immunity

Figure 1. Schematic picture of the attachment (a) and implantation of the blastocyst (b). Liljander et al. . Reproduced with permission of John Wiley and Sons.
Figure 2. Schematic drawing of the human placenta and organisation of the foetal membranes. The tree‐like structure of the villi constitutes the part of the placenta where maternofoetal exchange of nutrients and waste occurs. The yolk sac can be observed between the amnion and the chorion in early pregnancy. By the end of the third month, the amnion and chorion have fused. Liljander et al. . Reproduced with permission of John Wiley and Sons.


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Further Reading

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Thornton, Catherine A(Jun 2019) Placental Immune Defences – Protection against Rejection and Infection. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0001438.pub3]