Fig. 4

PHF Characterization, dosing methods, and PHF induced toxicity as measured via LDH. a Immunoblot showing enriched human PHF tau (PHF-1 staining) derived from an Alzheimer’s brain. b Neurons were exposed to PHF under one of four dosing paradigms. PHF was added alone, 24 h prior to antibody addition (PHF → Ab), together with antibody (PHF + Ab), or 24 h after antibody (Ab → PHF). Cells were washed with Neurobasal media between each step, and collection began 24 h after the last treatment applied. c In cells treated with 10 μg/ml PHF, LDH signal averaged 67 % above that of untreated controls (p < 0.01). 4E6 in the PHF + Ab and PHF → Ab paradigms significantly reduced LDH compared to PHF alone, and were comparable to untreated samples (11 and 15 % above control, p < 0.05), indicating that the antibody prevented toxicity. However, the Ab → PHF was not effective in reducing LDH signal (53 % above control) and showed no significant improvement over PHF alone samples. d All samples treated with 6B2 showed significantly higher levels of LDH relative to untreated controls (69, 59 and 79 % above control for the PHF + Ab, PHF → Ab, and Ab → PHF treatment groups respectively, p < 0.05). None of the treatments with 6B2 reduced LDH relative to PHF alone. e IgG was also not effective in preventing the increased LDH levels triggered by the addition of PHF. LDH in the PHF + Ab, PHF → Ab, and Ab → PHF groups was increased to 80, 43 and 61 % above control values (p < 0.05). None of the groups were significantly different from PHF alone. *: p < 0.05, **: p < 0.01, ***: p < 0.001