Comparative immunohistochemical characteristics of human choroid plexus in vascular and Alzheimer's dementia

Autoimmune alterations are indirectly supported in Alzheimer's disease by the demonstration of circulating antibodies directed to the epithelial basement membrane (BM) of the choroid plexus. We used immunohistochemical methods to compare the characteristics of choroid plexuses obtained postmortem from 15 patients. Six had a diagnosis of Alzheimer's disease, five had multi-infarct dementia (MID), and one suffered from mixed dementia. Similar tissue from three age-matched, non-demented controls was studied as well. Age-related psammoma bodies, lipofucsin, and flattened epithelial cells were present in all cases. Specific alterations were evident in Alzheimer's disease patients only. These were comprised of pseudolinear deposits of immunoglobulin (Ig)G and coarse deposits of C1q along the thickened and segmented epithelial BM, and were associated with IgM in five cases. Although no lymphoid infiltration was demonstrated, MHC Class II+ macrophages were observed in the plexus stroma, and numerous epithelial cells were class II+. These observations suggest that immune alterations, possibly of autoimmune origin, may be involved in Alzheimer's disease, leading to severe lesions of the choroid plexus. Such anomalies could be responsible for some of the alterations of cerebrospinal fluid (CSF) production or composition noted in this disease.