[HTML][HTML] Host defense and tolerance: unique challenges in the placenta

VB Zeldovich, AI Bakardjiev - 2012 - journals.plos.org
VB Zeldovich, AI Bakardjiev
2012journals.plos.org
Mammalian gestation creates an immunological paradox wherein the body must balance
tolerance of an allogeneic fetus with protection against invading pathogens. Pregnancy has
long been considered a state of immune suppression that, while necessary for reproduction,
increases a woman's susceptibility to infection [1]. However, mothers bear the responsibility
of the most important biological task: to carry and to nourish their offspring. It is therefore
fitting that a more nuanced picture is emerging of a tightly regulated maternal immune …
Mammalian gestation creates an immunological paradox wherein the body must balance tolerance of an allogeneic fetus with protection against invading pathogens. Pregnancy has long been considered a state of immune suppression that, while necessary for reproduction, increases a woman’s susceptibility to infection [1]. However, mothers bear the responsibility of the most important biological task: to carry and to nourish their offspring. It is therefore fitting that a more nuanced picture is emerging of a tightly regulated maternal immune system that balances awareness of the fetus with mechanisms to protect against pathogens and to sustain a healthy pregnancy [2]. Recent evidence indicates that innate placental defenses comprise one such mechanism. Subversion of these defenses by pathogens can lead to pregnancy complications such as preterm labor or vertical transmission with fetal morbidity or mortality [3]. The Danger Model posits that tissue damage rather than foreign antigens trigger inflammation [4]. This notion encompasses the paradox of mammalian pregnancy and suggests that infection-based loss of placental integrity may be the route to complications. Here we review recent evidence for innate placental barriers to infection and how these can be breached by pathogens.
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