C9orf72 immunoreactivity in the frontal cortex of Alzheimer's disease brains. Expression of chromosome 9 open reading frame 72 (C9orf72) studied in the frontal cortex of Alzheimer's disease brains by immunohistochemistry using sc-138763 and HPA023873 antibodies. (a) sc-138763, neurons and the neuropil. (b) HPA023873, neurons, the neuropil, and senile plaques (arrows). (c) HPA023873, senile plaque and surrounding astrocytes. (d) HPA023873, perivascular plaques with reactive astrocytes.