Fig. 7

4E6, but not 6B2, prevented increase in the tau/NeuN ratio caused by exposure to 10 μg/ml PHF. a–c Immunoblots probed with a pan-tau antibody of samples incubated with PHF or PHF in combination with a 4E6, b 6B2 or c control IgG1. d Quantitation of total tau levels in samples incubated with PHF and 4E6. With PHF alone, total tau levels decreased relative to control before recovering (29 % decrease at day 7). In contrast, samples in the PHF + Ab and PHF → Ab groups had significantly higher tau levels (48 and 51 % above control, p < 0.001 relative to PHF alone). Ab → PHF samples did not significantly differ from PHF alone. e After 7 days in culture, samples treated with PHF and 6B2 were not significantly different than the PHF alone samples. f The IgG1 treated cells also did not differ significantly from PHF alone. g We then used the values obtained from the NeuN data to normalize tau levels. Due to the substantial toxicity seen using LDH and NeuN immunoblotting, tau levels alone did not provide an accurate picture of the effects of PHF exposure. Incorporating NeuN data allowed us to account for neuronal loss when assessing changes induced by PHF. Using this method, it became evident that the remaining cells in the PHF group had significantly more tau (tau/NeuN) that control cells (5.6 fold increase, p < 0.0001). In the PHF + Ab and PHF → Ab groups, adjusted tau levels were comparable to control and significantly lower than the PHF alone samples (p < 0.0001). h When NeuN levels were controlled for, all 6B2 treated groups had tau levels significantly higher that controls with no significant difference from PHF alone group (p < 0.05-0.0001). i Controlling for NeuN did not alter the pattern of results seen in cells incubated with IgG