MAPT and Alzheimer disease: IHC using 3R- or 4R-specific anti-tau antibodies showed the induced tau pathologies in 6hTau mice recapitulated the isoform compositions in the original human tau strains since injection of AD-tau from two AD cases induced tau pathologies comprised of both 3R and 4R tau, while tau extracts from two PiD cases predominantly induced 3R tau pathologies.