Innate immunity in Alzheimer's disease: a model for local inflammatory reactions.

Over the past fifteen years, evidence has been accumulating that there is a chronic inflammatory reaction in areas of the brain affected by Alzheimer's disease. Chronic inflammation, which arises in reaction to an underlying pathology, represents a threat in its own right, wherever it may occur, and can in fact surpass primary affronts upon tissues. The brain, however, is particularly vulnerable because neurons are generally irreplaceable. In the case of Alzheimer's disease, inflammatory processes thus have the potential for turning a relatively slowly progressing condition into one characterized by rapid neurodegeneration.