Immunity system complexity: react within limits (Introduction)

by David Turell , Friday, July 16, 2021, 22:33 (1014 days ago) @ David Turell

The immune system reacts to fight pathogens, but must also react to stop any autoimmune dangerous actions:

https://medicalxpress.com/news/2021-07-immune-reactions.html

"When we are exposed to a pathogen, the immune system's B cells swarm to our lymph nodes, spleens, and tonsils. There, those cells mutate in germinal centers—microscopic boot camps that rush the B cells through volleys of mutations to produce the most potent antibodies for neutralizing the infectious agent. As long as a germinal center is up and running, B cells are free to mature and perfect their approach to fighting disease. But when a germinal center shuts down, usually after a few weeks, the training process grinds to a halt. Whatever antibodies happen to have formed by then are, for better or worse, the immune system's final product.

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"While B cells are the stars of any immune response, a supporting cast of T cells plays a crucial role within germinal centers. Helper T cells feed information to B cells and encourage their growth, while regulatory T cells suppress the entire process. "Helper and regulatory T cells are the gas and brakes of the immune response, respectively," Victora says.

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"In order to further explore the factors that lead to germinal center dissolution, Victora and his team began exploring a protein called Foxp3, which is vitally important for the function of regulatory T cells. By tagging Foxp3 green and germinal centers blue, the researchers were able to zoom in on individual germinal centers in mice and track each B cell bootcamp from its formation until its demise.

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"Upon closer examination, the scientists realized that the rising Foxp3 heralding the end of a germinal center's life was not coming from the regulatory T cells. Instead, the helper T cells themselves had begun expressing Foxp3—former gas pedals suddenly slamming the brakes, helpful promoters transforming into regulators just before the collapse of the germinal center.

"'We were seeing the helpers turn into regulators," Jacobsen says.

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"Extending the lives of our germinal centers after we receive a vaccine, for instance, may help coax our immune systems into making stronger antibodies. On the other hand, shutting down germinal centers may help treat autoimmune diseases—preventing the body from developing very strong antibodies that are potent enough target its own cells and do real damage."

Comment: Having too much immunity reaction can lead to autoimmunity diseases. This is obviously a designed system with obligatory start and stop controls by T calls. A start always needs a stop.