For decades scientists believed that so-called plaques and tangles, the postmortem evidence of a brain ravaged by Alzheimer's, were caused by the disease. (In the images above, plaques are the reddish structures- cells full of tangles are dark.) But more recent investigations suggest just the opposite: The formation of plaques and tangles probably causes the degenerative symptoms of Alzheimer's, not the other way around.
	Tangles occur inside of brain cells, while plaques are gummy globs that attach themselves to the outside of cells. The globs are molecules of a protein called beta-amyloid which floats in the space between cells. Most people can survive well into old age with a minimum buildup of beta-amyloid. But in those with a genetic pre-disposition the amyloid buildup occurs more quickly. The sticky protein binds to both neurons and supporting glial cells, causing an inflammatory response that eventually destroys neurons. The result is the onset of Alzheimer’s as early as the 40’s or 50’s.
	A number of research efforts are aimed at finding ways to halt or reverse the buildup of beta-amyloid. One approach that has shown promise in mice is a vaccine that causes the body's immune system to produce antibodies that mark beta-amyloid for attack by the brain‘s immune cells. Mice given the vaccine have shown significant reduction in plaque production.