APOE and Alzheimer disease: A previous study from our lab showed that a specific carboxyl-terminal truncated apoE4 fragment, apoE4[Δ(166–299)] (designated hereafter as apoE4-165) with a molecular weight of 19 kDa (a size within the range of molecular weights of carboxyl-terminal truncated apoE4 fragments found in brains of AD patients14, 15, 19) can promote the cellular uptake and accumulation of Aβ42 and leads to formation of reactive oxygen species (ROS)20.