Reducing microglial activity in the presence of apolipoprotein E4 (APOE4) has uncovered a mechanism associated with the deposition of misfolded amyloid and tau in a novel mouse model of Alzheimer’s disease. By transplanting human neurons into the mouse brain and eliminating the mouse microglia, scientists at the Gladstone Institutes in San Francisco observed that amyloid and tau deposition was reduced. These results support therapeutic strategies that target APOE4 and microglia.