Immunity system complexity: trained reactions in non-immune (Introduction)

by David Turell , Tuesday, July 27, 2021, 19:24 (1214 days ago) @ David Turell

It is found that regular cells (not B or T)can be naturally trained to fight:

https://phys.org/news/2021-07-cells-inflammation.html

"When a tissue experiences inflammation, its cells remember. Pinning proteins to its genetic material at the height of inflammation, the cells bookmark where they left off in their last tussle. Next exposure, inflammatory memory kicks in. The cells draw from prior experience to respond more efficiently, even to threats that they have not encountered before. Skin heals a wound faster if it was previously exposed to an irritant, such as a toxin or pathogen; immune cells can attack new viruses after a vaccine has taught them to recognize just one virus.

"Now, a new study in Cell Stem Cell describes the mechanism behind inflammatory memory, also commonly referred to as trained immunity, and suggests that the phenomenon may be universal across diverse cell types.

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"...there's a less specific strategy available to many cells, known as trained immunity. The impact is shorter-lived, but broader in scope. Trained immunity allows cells to respond to entirely new threats by drawing on general memories of inflammation.

"Scientists have long suspected that even cells that are not traditionally involved in the immune response have the rudimentary ability to remember prior insults and learn from experience. The Fuchs lab drove this point home in a 2017 study published in Nature by demonstrating that mouse skin that had recovered from irritation healed 2.5 times faster than normal skin when exposed to irritation at a later date.

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"They observed about 50,000 regions within the DNA of the stem cells that had unraveled to respond to the threat, but a few months later only about 1,000 remained open and accessible, distinguishing themselves as memory domains. Interestingly, many of these memory domains were the same regions that had unraveled most prodigiously in the early days of skin inflammation.

"The scientists dug deeper and discovered a two-step mechanism at the heart of trained immunity. The process revolves around transcription factors, proteins which govern the expression of genes, and hinges on the twin transcription factors known as JUN and FOS.

"The stimulus-specific STAT3 transcription factor responds first, deployed to coordinate a genetic response to a particular genre of inflammation. This protein hands the baton to JUN-FOS, which perches on the unspooled genetic material to join the melee. The specific transcription factor that sounded the original alarm will eventually return home; FOS will float away as the tumult quiets down. But JUN stands sentinel, guarding the open memory domain with a ragtag band of other transcription factors, waiting for its next battle.

"When irritation strikes again, JUN is ready. It rapidly recruits FOS back to the memory domain, and the duo charges into the fray. This time, no specific transcription factor is necessary to respond to a particular type of inflammation and get the ball rolling. The system unilaterally activates in response to virtually any stress—alacrity that may not always benefit the rest of the body."

Comment: Another layer of protection that helps us fight pathogens and injuries. We are born with some general protective agents, but our bodies have several types of cells that are designed to learn about new pathogens, and produce specific antibodies. In this case immunity is trained at a level that helps fight the bugs and repair wounds with general cells.