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Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Stress Hormone Shields Fetus
10 October 2001 7:00 pm
To survive in utero, the fetus must resist an onslaught by the mother's immune system that, most researchers agree, recognizes the father's share of the embryo as foreign and sometimes rejects it. Now, endocrinologists have determined that the principal soother of the maternal immune system is the same master hormone that commands the body's stress response. The results could help explain some infertility and recurring miscarriages.
Immunologists have long speculated that hormone changes early in pregnancy somehow alter the mother's immune system, but they couldn't pinpoint the mechanism. In the early 1990s, pediatric endocrinologist George Chrousos and his colleagues at the National Institute of Child Health and Human Development in Bethesda, Maryland, came across a clue. They found that corticotropin-releasing hormone (CRH), secreted by the hypothalamus to induce secretion of stress hormones by the pituitary and the adrenal glands, also appeared around sites of inflammation in adults. The correlation was so striking that the researchers decided to see whether CRH played a role in fetal implantation, which initially resembles an inflammation.
Chrousos's group looked for CRH in human trophoblast cells, special cells that help form the placenta, in petri dishes. Not only did the cells churn out CRH, they also harbored cell surface receptors for the hormone. CRH, in turn, triggered production of the cell surface protein FasL; trophoblasts expressing FasL then form a protective shield of sorts around the embryo by forcing any attacking immune cells to self-destruct. This suggested that blocking CRH should reduce the number of implanted fetuses--which, the team reports in the November issue of Nature Immunology, is indeed the case. When the researchers administered antalarmin, a CRH blocker, to pregnant rats during the first 6 days after conception, the number of implanted embryos was reduced by up to 70%. Chrousos thinks a potential cause of unexplained infertility or recurring early miscarriages in women might be due to a lack of CRH to prevent immune rejection.
While some scientists continue to question whether the fetus does kick off a maternal immune response, others are fascinated by Chrousos's findings. "Nobody has ever shown how FasL is induced" in the developing placenta, says reproductive immunologist Scott Kauma of the Virginia Commonwealth University in Richmond. "This adds to the importance of neuroendocrine hormones as key factors in regulating the maternal immune response" during pregnancy.