Brain injury may be autoimmune phenomenon, like multiple sclerosis

Mar. 6, 2013 Most scientists are starting to agree that repeat, sub-concussive hits to the head are dangerous and linked to neurological disorders later in life. A new collaborative study, though, attempted to find out why -- and discovered that damage to the blood-brain barrier and the resulting autoimmune response might be the culprit.

Published in journal PLOS ONE by the University of Rochester Medical Center and the Cleveland Clinic, the research suggests a new way of thinking about concussions: That the brain degeneration observed among professional football players (including the much-publicized chronic traumatic encephalopathy) could result from an out-of-control immune response, similar to what multiple sclerosis patients experience. If so, this opens the door to investigating a vaccine or drug therapy to prevent head trauma.

Although he emphasized that the research is preliminary, co-author Jeffrey J. Bazarian, M.D., M.P.H., associate professor of Emergency Medicine at URMC, said it's exciting to discover a theory that appears to fit with the reality of what experts observe among athletes. Bazarian worked closely with lead investigator Damir Janigro, Ph.D., professor of Molecular Medicine at the Cleveland Clinic, and 67 college football players from northeast Ohio and Rochester, N.Y., who agreed to participate in the research.

"Although the awareness of sports-related concussions is much higher, we still know very little about the long-term consequences and what happens inside the brain," Bazarian said.

"Our theory is plausible as an explanation for how routine head hits that come with playing football can lead to severe neuro-degeneration later in life," said Bazarian, a national expert who has served on an Institute of Medicine committee for brain injury. "If others confirm this, it could present options with drugs that influence the immune response."

The blood-brain barrier is like a semi-permeable gate between the brain and bloodstream. No other organ has such a barrier. When the barrier is working properly, it holds in proteins and molecules that bathe the brain and protect it from foreign substances. With blows to the head, however, the barrier opens slightly and allows some proteins to leak into the bloodstream.

Researchers found that S100B, a well-accepted protein biomarker for traumatic brain injury, was present in varying degrees in the blood samples of the 67 football players after every game -- even though none of them suffered a concussion. This demonstrates that even the most routine hits have some impact on the blood-brain barrier and possibly the brain itself, Bazarian said.

For the purposes of this project, however, the team wanted to explore what happens after S100B surges from the brain and enters the bloodstream. Again, they made an important finding -- that the body views S100B as an enemy and begins to form antibodies against it as if it were a virus.

Researchers hypothesized that a buildup of antibodies would result in a more vigorous attack on S100B in the bloodstream. But in the process, they learned, some antibodies sneak back through the damaged blood-brain barrier to the brain and begin to harm the healthy brain cells that produced the S100B protein in the first place. This is analogous to a missile searching for a target, Bazarian said, with some unintended targets eventually falling under attack.

Researchers also showed that S100B accumulates in dendric cells, which regulate auto-immune responses. Therefore, as the blood-brain barrier repeatedly opens during the football season it might set the stage for a continuous autoimmune-type attack on the brain, they reasoned.

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Brain injury may be autoimmune phenomenon, like multiple sclerosis