MAPT and tauopathy: There is mounting experimental evidence that tauopathies can progress by inter-cellular transmission prionoid mechanisms [23, 32, 36] and can be secreted in a diseased brain; consequently tau immunotherapies have been successful in mitigating or halting tauopathy in preclinical models [3–7, 12, 13, 22, 30, 44, 45, 48].