Fig. 1. Transportation of tau from the brain to blood.

(a–b) Mice were intracerebroventricularly injected with ¹²⁵I-labeled tau 2N4R (I-Tau). Brain (a) and blood plasma (b) were then collected at indicated time points after injection. Levels of radioactivity in the samples were determined using a gamma counter. See also Supplementary Fig. 1a for the early phase efflux kinetics of I-Tau. (c) Blood was collected at 60 min after injection, followed by anti-L1CAM immunocapture of exosomes from platelet-free plasma. Normal mouse IgG-captured (mIgG) or “Empty” (no bead “capture”) samples were used as controls. Levels of radioactivity were measured in the whole brain, the whole plasma, the plasma L1CAM-containing exosome fraction (Exo), and the exosome-less fraction (supernatant after immunoaffinity capture; Super). Data shown are mean ± S.D. from 4–6 mice at each time point. CPM, counts per minute.