In immunocytochemical studies, the CSF from Parkinson disease (PD) patients and from Alzheimer disease (AD) patients were investigated for the presence of neuron specific antibodies using dopaminergic and cholinergic neuronal cultures from embryonic rat brain, respectively. Dopamine containing cell bodies were labelled by Parkinsonian CSF-IgG, while cholinergic neurons, identified with a-NGF-receptor antibodies, were recognized by CSF from AD-patients. The CSF from PD-patients was investigated after autologous adrenal transplantation. CSF was removed 7 d, 5 months and 1 year after operation. When added to 18 d neuronal cultures for 3 d, the 7 d CSF caused neuronal cell and a glial reaction. The 4 months CSF caused cell death, but markedly less than the 7 d CSF. One year after transplantation the CSF had no toxic effects; these cultures were similar to control cultures. It is concluded that CSF from PD patients may contain aggressive IgG-species specific for DA neurons, and that the amount of such antibodies decrease after adrenal transplant operations. It is suggested that neurodegenerative diseases may become aggravated by autoimmune reactions.