Immunity complexity: eosinophiles protect the gut (Introduction)

by David Turell , Friday, June 17, 2022, 19:28 (889 days ago) @ David Turell

Eosinophiles, very active in allergies have an important role in the gut:

https://medicalxpress.com/news/2022-06-bad-guy-blood-cells-vital.html

"'The study showed a critical role for eosinophils in facilitating mutualistic interactions between host and microbiota, the millions of bacteria in the gut," Professor Harris said. "It turns our views of eosinophil function on its head and will no doubt spur a lot more research into these relatively rare cells," she said.

"Eosinophils make up about 1–2% of circulating white blood cells in healthy people in developed countries but are present in increased numbers in people who are severely allergic. "They play a tissue-destructive, pathological role in these allergies, they're the bad guys," Professor Harris said.

"Around 10–15 years ago scientists realized that eosinophils accounted for 10–30% of white blood cells in the gastrointestinal tract and asked why. The answer has remained a mystery, Professor Harris said. "We set out to answer why these supposedly tissue-destructive cells were sitting in the gut."

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"They found that eosinophils coordinated the gut's response to bacteria.

"'They were limiting overt inflammation and by doing that they were limiting tissue damage," Professor Harris said. "The most important factor of this damage is the length of the villi, the finger-like projections that come up from the wall of the intestine, which absorb nutrients.

"'We found eosinophils kept those villi intact and without them the villi became much shorter and lipid uptake was reduced.

"'So, they were helping to maintain this absorptive area that allowed extraction of nutrients from the diet at a proper level."

"The study also found that gut motility was dysregulated in the absence of eosinophils and that they could impact the structure of tissue."

Comment: the immune system doesn't just fight infections, but acts as an important protection mechanism in the gut. The gut microbiome is essential, but if a nasty bug is not held in check, severe infections can happen. A stepwise chance development is very unlikely as compared to design.