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Immunology of the maternal-fetal interface

Vikki M Abrahams, PhD
Section Editors
E Richard Stiehm, MD
Charles J Lockwood, MD, MHCM
Deputy Editor
Elizabeth TePas, MD, MS


In pregnant women, local adaptation of the maternal immune system allows for successful coexistence between the mother and the semi-allograft that is the fetus/placenta expressing both maternal (self) and paternal (nonself) genes [1-4]. Cytotoxic adaptive immune responses are diminished, bypassed, or even abrogated, while regulatory adaptive immunity is enhanced [5,6]. By contrast, innate (natural) immunity remains intact, serving two purposes: one, to continue to provide host defense against infection, and two, to interact with fetal tissues to promote successful placentation and pregnancy [4,7-10].

An introduction to the immunology of pregnancy and the maternal-fetal interface is presented in this topic review. Basic immunologic concepts are reviewed separately. (See "An overview of the innate immune system" and "The adaptive cellular immune response".)


The placenta and fetal membranes are directly exposed to maternal blood and tissues. Thus, unique features of the cells that comprise this interface must underlie the remarkable ability of the genetically distinct fetal tissue to inhabit the maternal host.

Not all immunologists studying reproduction agree that maternal immunity is solely antagonistic to trophoblast tissue. Alternative views have been expressed [11,12], some of which are described below. Indeed, a maternal immune presence in the decidua is essential for successful implantation [4]. Evidence of the opposite hypothesis (ie, that trophoblasts have offensive mechanisms for killing maternal lymphocytes) is also lacking. It is clear, however, that the placenta is normally protected from the killing functions of maternal cells. This protection may result from synthesis of soluble receptors (tumor necrosis factor [TNF]-alpha), display of nonfunctional receptors (Fas), and expression of decoy receptors (TNF-related apoptosis-inducing ligand [TRAIL] death domain-containing receptors DcR1 and DcR2) [13-16].

Fetal trophoblast cells — Fetal trophoblast cells are the specific cell layer that protects the embryo from those components of the maternal immune system dedicated to destroying foreign tissues. The inner cell mass and resultant embryo are secluded and protected beneath a layer of trophoblastic cells throughout pregnancy.

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Literature review current through: Dec 2017. | This topic last updated: Jan 31, 2017.
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