Here is an interesting article from Newsday that gives us some reason to be
hopeful that new lines of treatment may be available some day:
LI researchers find brain, immune system link
BY JAMIE TALAN
STAFF WRITER
September 23, 2004
Long Island scientists have discovered a direct connection between the brain and
the immune system, a finding that could have implications for many diseases.
Until recently, scientists believed the brain interacted with the immune system
only indirectly by releasing chemicals into the bloodstream.
But Dr. Kevin Tracey, a professor and head of the center for patient-oriented
research at the North Shore-Long Island Jewish Research Institute in Manhasset,
found that the vagus nerve, in the brain stem, talks directly to the immune
system, which is spread throughout the body.
Once this relationship is understood, Tracey said, it could open a way to
prevent immune diseases by altering brain responses, or to treat diseases by
tweaking the immune system so that it does not over-respond causing
inflammation.
This week, Tracey hosted a meeting on the new link at the Karolinska Institute
in Stockholm. To test this direct circuit between the brain and the immune
system, Tracey devised a study to trick the brain's immune response to a lethal
bacteria called endotoxin. Normally, an animal reacts to an injection of
endotoxin by mounting a massive immune response that kills the animal as it
tries to kill the toxin. This is similar to an autoimmune disease, in which the
body's immune system goes into overdrive, attacking the body itself. Tracey and
his colleagues found that blocking the vagus nerve prevented the lethal response
to the endotoxin.
Then, they attempted to figure out how the communication takes place.
The vagus nerve is named for its Latin root "to wander." From the brain stem,
the nerve snakes all over the body's major organs, the heart, spleen, liver and
kidneys. Most cells of the immune system also are found in these organs. The
vagus nerve releases a neurochemical signal that produces an electrical current
across the nerve. The chemical, acetylcholine, floats a short distance and lands
on cells of the immune system called macrophage. When acetylcholine lands on
docking receptors on the macrophage, immune cells turn off. The result: No
massive immune response to the normally lethal endotoxin.
This is the first time the brain chemical acetylcholine has been linked to the
immune system's anti-inflammatory response. This brain chemical is depleted in
Alzheimer's disease and inflammation is often noted in the brains of patients.
Tracey believes that the brain's regulation of acetylcholine is responsible for
its anti-inflammatory properties. He is embarking on a pig study to see whether
stimulating the vagus nerve blocks inflammation.
Crohn's disease, rheumatoid arthritis, and inflammatory bowel disease are
examples of sickness caused by a wildly overactive immune system. That the vagus
nerve can enhance acetylcholine and shut down an abnormal immune response offers
hope for new treatments for many conditions, he said.
At North Shore, Tracey is bringing volunteers into the laboratory and measuring
their vagal nerve activity. His hunch is that a robust vagus nerve response will
be a sign of good mental and physical health.
Copyright © 2004, Newsday, Inc.