Thoughts can cause real illnesses

The brain not only helps regulate immune responses, it also stores and retrieves “memories” of them. A team of scientists from the Technion-Israel Institute of Technology (Israel) has discovered, in an experiment with rodents, that the brain has the power to trigger physical diseases, but also to contain them.

Conditioning that extends to immune responses

The peripheral immune system is armed with a massive battalion of proteins, cells, and entire organs, such as the spleen, that protect invaders. But how does the peripheral immune system affect neuronal activity?

Immune cells in the periphery are known to routinely patrol the central nervous system and support its function. Now, scientists have shown, for the first time, that just as the brain remembers people, places, smells, etc., it also stores what they call “memory traces” of past infections in the body . Reactivating the very brain cells that encode this information is enough to quickly summon the peripheral immune system to defend the tissues at risk.

Thus, using state-of-the-art genetic tools in mice, the researchers identified brain neurons in a group of laboratory mice that were activated during experimentally induced inflammation in the abdomen. They studied strains of mice with a type of intestinal inflammation known as colitis – giving them a chemical in drinking water to test for colitis – and used fluorescent markers to take snapshots of clusters of brain cells in the insular cortex that were activated during infection. . They used a second genetic tool to do something more powerful: They put a molecular on / off switch on activated insula cells, showing that restimulation of those neurons could trigger the same types of inflammation again.

So, several weeks after the colitis subsided and the mice recovered, the researchers used the on / off switch to reactivate neurons and unleash a similar inflammatory response in the colon. They saw similar results in mice that had been induced to develop a different inflammatory disease, peritonitis, in the abdominal lining (as if they had colitis again).

The brain, inseparable from the immune system

“This suggests that the brain stores some kind of representation of the inflammatory conditions that mice experience, and has a way of causing the same inflammation a posteriori” , explains Professor Asya Rolls, neuroimmunologist and leader of the work published in the journal Cell, to the Israeli newspaper The Times of Israel.

In essence, this is not entirely surprising . Otherwise, for example, vaccines would not work if the peripheral immune system was not able to retain information about infections that we have suffered in the past in order to combat future ones. But what these scientists have discovered goes one step further: the brain can actually store these traces of immune activity and use them to trigger a very precise response.

Although this is a basic study in mice, and there are multiple challenges in translating this concept to humans, these discoveries could help treat chronic inflammatory conditions such as Crohn’s disease, psoriasis, and other autoimmune conditions, reducing your memory trail in the brain, according to experts.

Referencia: Insular cortex neurons encode and retrieve specific immune responses. Tamar Koren et al. Cell, November 08,2021. DOI:https://doi.org/10.1016/j.cell.2021.10.013