MAPT and tauopathy: Regarding the specific antibodies examined herein, 4E6 and 6B2, we have previously shown that both are readily taken up into tauopathy mouse neurons in brain slices and primary culture models, where they colocalize with tau primarily in the endosomal lysosomal system, and clear soluble tau, with 4E6 more consistently being effective in clearing pathological tau and preventing its toxicity (7, 12, 14, 23).