Abstract
: β‐Amyloid (Aβ) peptides are a key component of the senile plaques that characterize Alzheimer's disease. Cytokine‐producing microglia have been shown to be intimately associated with amyloid deposits and have also been implicated as scavengers responsible for clearing Aβ deposits. However, little is known about the initial activation of these microglia or the effect of Aβ on phagocytosis. Murine BV‐2 microglia were used to assess the effect of synthetic Aβ 1–42 on phagocytosis by quantifying uptake of fluorescent microspheres, acetylated low‐density lipoproteins, and zymosan particles by flow cytometry. Aβ 1–42 stimulated microglial phagocytosis in a time‐ and dose‐dependent manner. Aβ fibrils produced the greatest potentiation, and once activated, phagocytosis remained elevated after removal of Aβ from the cultures. Aβ‐stimulated phagocytosis could be blocked if proteoglycans were first complexed to Aβ fibrils. These data suggest that Aβ fibrils act as an immune signal to stimulate microglial phagocytosis and that extracellular matrix molecules may modify Aβ function.