Antibodies in cerebrospinal fluid of some Alzheimer disease patients recognize cholinergic neurons in the rat central nervous system.

The etiology of Alzheimer disease is unclear. However, immunological aberrations have been suggested to be critical factors in the pathogenesis of this neurodegenerative disease. This study was carried out to investigate if cerebrospinal fluid (CSF) from Alzheimer disease patients contains antibodies that recognize specific neuronal populations in the rat central nervous system. The results indicate that in a subgroup of patients this is indeed the case. The antibodies reported in this study have the following properties: (i) they recognize neuronal populations and components in the medial septum and spinal motor neurons in rats perfused with a mixture that fixes small neurotransmitter molecules; (ii) adsorption of the patient CSF with staphylococcal protein A-Sepharose and using a polyclonal antiserum against human IgG3 indicates that the immunocytochemical reaction in these brain regions is mainly due to the subclass IgG3; and (iii) the CSF immunocytochemical reaction is blocked by preincubation of the sections with a rabbit anti-acetylcholine antiserum. These results provide evidence that antibodies in the CSF of some, but not all, Alzheimer disease patients recognize acetylcholine-like epitopes in cholinergic neurons in the rat central nervous system.