Figure 9.

α-hP₁₁ autoantibodies induce neuronal apoptosis in vitro and in vivo. (A) α-hP₁₁ antibodies induce apoptosis in neurons in primary culture. Cells were incubated with 100 μg/ml of control IgG or 0.5 μg/ml of α-hP₁₁ for 48 h. Indirect immunofluorescence against activated caspase-3 revealed apoptosis. (B) α-hP₁₁ antibodies decrease neuronal viability. MTT assays show a concentration-dependent loss of viability. In contrast with the 30% viability loss caused by 0.5 μg/ml of an IgG fraction from a normal individual, the same concentration of α-hP₁₁ lowered the viability by ∼90%. For comparison, H₂O₂ at 50 μM decreased the viability by 80%. Error bars represent the mean ± SEM. (C) α-hP₁₁ antibodies induce apoptosis in neurons in situ. The rat brain cortex was injected with 0.7 μg of either control IgG or α-hP₁₁ in contralateral sides, fixed after 24 h, and either stained with Cresyl violet or treated for immunohistochemistry of activated caspase-3. The region injected with α-hP₁₁ shows caspase-3 activation (bottom right and inset) and lower cell density (top right) and. Bars, 100 μm.