Immunity complexity: gut organisms direct T cells (Introduction)

by David Turell , Wednesday, March 15, 2023, 19:18 (618 days ago) @ David Turell

new surprising discovery:

https://www.the-scientist.com/news-opinion/gut-bacteria-help-t-cells-heal-muscle-study-...

"According to a study published February 22 in Immunity, T cells that normally reside in the mouse colon play a crucial role in tissue regeneration—and rely on gut microbes to do so. Without these helpful microbes, the study suggests, inflammation could get out of control, preventing healing and causing fibrosis.

“'The main message of the paper is that the microbiota is influencing your immune system and your general health in a way larger way than we appreciated before,” says Bola Hanna, an immunologist at Harvard Medical School. Hanna studies regulatory T cells, a class of immune cells found in tissues throughout the body. He describes regulatory T cells as the “peacekeepers” of the immune system because they rein in other immune cells, ensuring inflammation doesn’t get out of control.

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"Colon T cells have many roles, including ensuring that the other immune cells don’t attack the helpful microbes living there. They also play a role in metabolism and digestion.

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"The cells didn’t just go to the muscle; they traveled to other areas of the body, including the organs, the team observed. And after an injury, tagged cells appeared in the damaged tissue, suggesting that cells from the colon had indeed traveled to the muscle.

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"Using flow cytometry, they found higher levels of IL-17, an inflammatory cytokine, in the wounds of these mice following injury in comparison to normal mice. Unregulated levels of IL-17 have been linked to delayed wound healing.

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"Hanna calls the finding that gut microbes play a pivotal role in wound healing “really cool.”

"The team also explored the role of gut-derived regulatory T cells in other forms of healing, finding that these microbiota-activated cells don’t just help muscles heal after injury; they also work to heal the liver from damage. In mouse models of nonalcoholic fatty liver disease, regulatory T cells helped slow inflammation, and their functioning was dependent on the microbiome.

"Hanna says that “this work raises a question about the use of antibiotic treatment, since colon regulatory T cells are highly dependent on microbiota. We might have to be judicious about whether we use antibiotics in the case of tissue injury.” This might be especially relevant to patients just after surgery or those with severe wounds, since both groups often receive antibiotics. In addition, IL-17 is linked to autoimmune disorders and increased tumorigenesis, meaning the gut could also play a role in other inflammatory disorders.

“I’m personally intrigued by the beauty of this cross-communication that we have in our body,” says Hanna. “They are impacting us in ways beyond our understanding.”

Comment: Those T cells, exposed to all sorts of varieties of bacteria, are excellent candidates for recruitment to fight bacteria. An example of designed automatic action. There are too many parts for chance mutations to create this mechanism.