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Fetal–Maternal Immunological Relationships

  1. Gérard Chaouat

Published Online: 17 DEC 2012

DOI: 10.1002/9780470015902.a0000516.pub3



How to Cite

Chaouat, G. 2012. Fetal–Maternal Immunological Relationships. eLS. .

Author Information

  1. Hopitalk Sainr, U 976 INSERM, Louis, Paris, France

Publication History

  1. Published Online: 17 DEC 2012


Despite inheriting half of its genetic material from its father, the fetoplacental unit is not rejected by the maternal immune system because of a unique immunological relationship with the mother. Despite maternal immune recognition of the conceptus as evidenced by alloantibodies, unlike for conventional allografts, the immune response is spared, cytotoxic effectors being downregulated or suppressed, whereas several cytokinic responses, including inflammatory ones, are used or even provoked for their preimplantation or later on ‘immunotrophic’ effects. This unique relationship is partly due to the peculiar antigen expression in the placenta, culminating in humans with the sole expression of human leucocyte antigen C (HLA-C) and monomorphic HLA-G on invading cytotrophoblasts and also many immunoregulatory pathways, with special emphasis presently put on regulatory T cells. Moreover, uterine natural killer (uNK) cells are a distinct, specialised NK subset, endowed with immunoregulatory and angiogenic properties, necessary for local (spiral) arteries development. Consequences for abortion eclampsia are discussed, as well as antibody-induced fetal haemolytic disease.

Key Concepts:

  • The fetus is usually seen as an allograft in mother's womb, which should be rejected by the maternal immune system.

  • Pregnancy induces systemic modifications in the maternal immune system but these do not really account for fetal survival.

  • Recognition of the ‘foreign’ nature of the fetus is good and even sometimes required for successful pregnancy.

  • Placenta acts as a barrier between the fetus and maternal cells.

  • Uterine natural killer cells are not endowed with the same properties as the ones found in peripheral blood.

  • One of the keys to fetal survival is the peculiar expression of MHC antigens in the placenta, including in human the expression of a nonpolymorphic antigen, HLA-G, in membrane bound and soluble forms both endowed with immunoregulatory properties.

  • Uterine natural killer cells control local uterine angiogenesis.

  • The placenta bathes in/secretes immunotregulatory materials.

  • Regulatory T cells mitigate the effects of allorecognition by maternal immune system in placental mammals.

  • Allopregnancy is a Th2 phenomenon.

  • In variance with MHC antigens, red blood cells antigens can induce maternal antibodies which can cross the placenta, and destroy in utero fetal red blood cells.


  • placenta;
  • graft;
  • antigen expression;
  • rejection;
  • tolerance;
  • abortion;
  • eclampsia;
  • tregs;
  • uNK;
  • angiogenesis;
  • RH haemolytic disease