How the Gut Protects the Brain

Everyone wants to talk about the gut-brain axis these days for good reason.  So many brain diseases are being found to have contributing factors originating in the intestinal tract that other are searching for more connections.  Mostly we have a lot of correlations, meaning we know there is a connection, but don’t have a mechanism to explain the connection.  Researchers from the University of Cambridge can now offer a probable mechanism to explain how the gut helps to protect the brain from infections.

The immune system possesses numerous means of responding to microbial invaders, but may be best known for its production of antibodies which bind to the invader, marking it for destruction.  This works great throughout the body, but the brain does not have the B cells which make antibodies in its tissue.  There are at most plasma cells, the fully activated B cell antibody factory, which resides near the blood vessels going through the brain.

Besides their location, these plasma cells stand out from the rest of the body’s plasma cells.  Normally, plasma cells secrete a type of antibody called IgG into the blood stream to fight invaders.  The brain’s plasma cells secrete IgA antibodies like those found in the gut or other mucosal surfaces.  These antibodies work at intestinal surfaces as more of a swat team to go outside the tissues and blood stream to fight invaders before they get through the barrier defenses.

This discovery came from mouse studies.  Mice without bacteria in their guts did not have the IgA secreting plasma cells in their brain.  In another experiment, removal of the IgA producing cells in the mice brains allowed infections to enter the brain more easily showing these cells to be critical for the blood brain barrier.  It appears that B cells are activated in the intestines by stool bacteria and likely migrate into the brain where they offer important protection from infections in the brain.

Functional medicine already works tirelessly to apply ground-breaking research like this to our patients every day.  We have known for a while that gut health plays a central role in restoring patients’ health whether related to brain disease, autoimmune disease, viral immunity, joint inflammation, or other conditions.  Helping patients live healthier, more abundant lives requires working with the whole body and its interwoven complexity.  That’s why we never, ever ignore a patient’s gut health as we care for them in our clinic.

 

Original Article:

Fitzpatrick, Z et al. Gut-educated IgA plasma cells defend the meningeal venous sinuses. Nature, 2020 DOI: 10.1038/s41586-020-2886-4

Thanks to Science Daily:
University of Cambridge. “Why protecting the brain against infection takes guts.” ScienceDaily. ScienceDaily, 4 November 2020. <www.sciencedaily.com/releases/2020/11/201104121444.htm>.


Sanctuary Functional Medicine, under the direction of Dr Eric Potter, IFMCP MD, provides functional medicine services to Nashville, Middle Tennessee and beyond. We frequently treat patients from Kentucky, Alabama, Mississippi, Georgia, Ohio, Indiana, and more... offering the hope of healthier more abundant lives to those with chronic illness.

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