White matter amyloid in Alzheimer's disease brain.

Amyloid beta-protein (A beta) deposits in the white matter were investigated by the double immunohistochemical staining for A beta and neuritic, glial or vascular components. Reactive astroglia and neurite abnormality were absent around A beta deposits in the white matter (w-A beta) even those with a core. The association of w-A beta with blood vessels was not consistent. Aggregates of activated microglia were found to be the sole but a consistent accompaniment of A beta deposits even in the absence of other components such as neuron, synapse, neurite abnormality and reactive astroglia, as observed in the white matter. This suggests that the aggregates of activated microglia most likely represent one of the factors promoting the process of A beta deposition.