In addition to Aβ and tau pathology, neuroinflammation has been suggested to be one link between APOE mediated increased risk for AD; Since APOE is mainly expressed in astrocytes and microglia, the cells responsible for important immune functions in the CNS, APOE ε4 is likely to have also a direct effect on glial functions, independent of Aβ or tau (17). Here, APOE is linked to Alzheimer disease.