Biochemical controls: protect a pregnancy (Introduction)

by David Turell , Monday, May 06, 2024, 17:47 (13 days ago) @ David Turell

A pretend infection protects the placenta:

https://www.quantamagazine.org/during-pregnancy-a-fake-infection-protects-the-fetus-202...

"The study showed how the placenta — the embryonic organ that connects offspring and mother — uses a molecular trick to feign illness. By pretending it’s under viral attack, it keeps the immune system running at a gentle, steady pace to protect the enclosed fetus from viruses that slip past the mom’s immune defenses.

"The discovery suggests that prior to infection, some cells may be able to activate a subtle immune response that can provide moderate protection in delicate tissues.

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Because antiviral immune weapons can destroy tissues, cells typically turn them on only when there’s an active threat like an infection, Kagan said. Then, once the infection clears, those weapons are turned off as quickly as possible.

"But the placenta breaks these rules, according to the new research. Somehow, it turns on defenses before they are necessary and then leaves them on without harming itself or the fetus.

“'It protects but doesn’t damage,” said Hana Totary-Jain, an associate professor of molecular pharmacology at the University of South Florida in Tampa and lead author on the new paper. “Evolution is so smart.”

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'After years of careful experiments, Totary-Jain’s team showed that in the placenta, transcripts of Alu repeats formed snippets of double-stranded RNA — a molecular silhouette our cells recognize as viral in origin. Sensing the fake virus, the cell responded by producing interferon lambda.

“'The cell is effectively dressing up as an infectious agent,” Kagan said. “The result is that it convinces itself that it’s infected, and then operates as such.”

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"In most tissues, Alu sequences are highly suppressed so that they never get a chance to mimic a viral attack. And yet that is the exact scenario the placenta seems to create on purpose. How does it balance the health of the growing embryo with a potentially risky immune response?

"In experiments with mice, Totary-Jain’s team found that the placenta’s double-stranded RNAs and ensuing immune response didn’t seem to hurt the developing embryos. Instead they protected the embryos from Zika virus infection. The placental cells were able to toe the line — conferring protection on the embryos without cuing a self-destructive immune response — because they called in the gentler defenses of interferon lambda.

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"How placental cells manage to activate only interferon lambda, keeping the immune response simmering but never boiling over, is still a mystery. But Totary-Jain has an idea about why placental cells evolved this trick that other cells seemingly avoid: Since the placenta is discarded at birth, perhaps it can afford to take immune risks that other tissues can’t.

"The findings reveal a new strategy the placenta has for protecting the fetus, apart from mom’s immune system. Since the mother’s immune response is dampened during pregnancy to prevent attacks on the genetically distinct embryonic cells, the placenta has had to develop extra defenses for the growing baby it supports."

Comment: as humans we can appreciate the concept. The purpose is clear but how could this naturally happen? Trial and error would be disastrous. It reeks of a designer mind at work.