MAPT and Alzheimer disease: There is mounting evidence that microglia protect against the incidence of AD, as impaired microglial activities and altered microglial responses to β-amyloid are associated with increased AD risk; activated microglia also appear to be harmful to neurons and can exacerbate tau pathology and secrete inflammatory factors that can injure neurons, either directly or through the activation of neurotoxic astrocytes [23].