MAPT and Alzheimer disease: This intermediate seeding activity was also observed with the original AD tau RT-QuIC assay (logSD50/mg tissue: KO < PiD and 4R tauopathies < AD, Table 1) [21], but not in the 3R or 4R tau RT-QuIC assays (compare control logSD50/mg tissue values in 3R, 4R tau RT-QuIC columns with KO averages in Table 1) [27, 29].