“The cells are effectively masquerading as infectious agents,” Kagan said. “The result is that the virus thinks it’s infected and behaves that way.”
boiling immunity
Immune responses can be destructive, especially antiviral responses. Viruses are most dangerous when they have already entered cells, so most immune strategies that target viral infections work in part by damaging and killing infected cells.
Therefore, the cell screams, “It’s a virus!” At your own risk. In most tissues, Alu sequences are highly repressed and do not have the opportunity to mimic viral attack. But that’s exactly the scenario that the placenta seems to create on purpose. How do we balance the health of the developing embryo with a potentially dangerous immune response?
In experiments with mice, Totaly-Jain’s team found that double-stranded RNA in the placenta and the subsequent immune response did not seem to harm the developing embryo. Instead, they protected the embryos from Zika virus infection. Placental cells called on the milder defenses of interferon lambda, allowing them to walk the fine line between providing protection to the embryo without triggering a self-destructive immune response.
Typically, the first responders to double-stranded Alu RNA escape are type I and type II interferons, which rapidly recruit destructive immune cells to the site of infection, causing tissue damage and even autoimmune diseases. Interferon lambda, on the other hand, is a type III interferon. It acts locally by communicating only with cells within the tissue, generating a mild immune response that can last for a long time within the placenta.
How placental cells are able to activate only interferon lambda and keep the immune response boiling over without boiling over is still a mystery. But Totally Jains have an idea as to why placental cells have evolved this trick that other cells seem to avoid. Because the placenta is discarded at birth, it may be able to take on immune risks that other tissues cannot.
The findings reveal that the placenta has a new strategy to protect the fetus, independent of the mother’s immune system. During pregnancy, the mother’s immune response weakens to prevent attack on the genetically distinct embryonic cells, so the placenta had to develop special defenses for the growing baby.
However, this trick, the low-level immune response generated by the fake virus, may not be limited to the placenta. Researchers at Columbia University recently reported a similar phenomenon in neurons.They observed RNA from different genomic elements tied together It becomes double stranded and triggers an immune response. In this case, the immune system called in the more destructive type I interferon, but the levels produced were low. The authors speculated that chronic low-level inflammation in the brain may control infection and prevent major inflammation and neuronal cell death.
So this kind of immunity ploy may be more common than anyone thought. By studying how the immune system breaks its own rules, scientists can better define what those rules are in the first place.
original story Reprinted with permission from Quanta Magazine, Editorially independent publication simmons foundation Its mission is to enhance the public’s understanding of science by covering research developments and trends in mathematics, physical sciences, and life sciences.
