The amino-terminally truncated forms of amyloid beta-protein in brain macrophages in the ischemic lesions of Alzheimer's disease patients.

We have investigated the cerebral cortex of Alzheimer's disease in which small infarcts are found on postmortem neuropathological examination. In areas that have been subjected to recent ischemia, immunohistochemical staining for amyloid beta-protein (A beta) is much less intense than in the non-ischemic surround. However, the infiltrating brain macrophages contain granules immunopositive for C-terminal fragments of A beta. The immunohistochemical profile indicates that A beta in these granules lacks epitopes in the N-terminal fragments. These data suggest that appropriately stimulated macrophages can phagocytose A beta deposits and that digestion of the N-terminal region is an early consequence of this phagocytosis.