From the article:
A new study suggests that brain injury from repeat blows to the head – observed among football players and soldiers – might not be a traumatic phenomenon, but an autoimmune phenomenon. It indicates that brain injury may be the result of an out-of-control immune response, much like multiple sclerosis. This is an entirely new way of thinking about how trauma could cause long term degeneration and opens the door to investigating a vaccine/drug to prevent head trauma.
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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.