Diffuse plaques in the molecular layer show intracellular A beta(8-17)-immunoreactive deposits in subpial astrocytes.

The presence of A beta protein- (A beta) containing astrocytes in diffuse plaques of the cortical layers II-VI has recently been demonstrated with antibodies directed against A beta(17-23) and C-terminal epitopes, of A beta. We here confirm and extend this finding by use of immunocytochemical double-labeling and preembedding immune-electron microscopy. Diffuse subpial plaques are associated with both anti-A beta(8-17) and anti-A beta(17-23)-positive granules in astrocytes. The ultrastructural nature of these intracellular deposits has been demonstrated to be lysosomal and the deposits have a lipofuscin-like appearance. These data point to a role of subpial astrocytes in the degradation of A beta by lysosomal processing.