APOE and Alzheimer disease: Although some subtypes of APOE can remove potentially toxic β-amyloid (Aβ) in the brain during AD through apoptotic programmed cell death and the exposure of cellular phosphatidylserine (PS) membranes that can attract microglia for toxin removal, APOE-ε4 does not inhibit Aβ aggregation and may add additional disability by permitting viral antigen infection.