Distribution of beta amyloid associated proteins in plaques in Alzheimer's disease and in the non-demented elderly.

Recent studies have shown that cerebral beta amyloid (A beta) protein deposition is a necessary, but not sufficient, factor to develop the pathology of Alzheimer's disease (AD). In the present immunohistochemical study, we have investigated in AD the distribution of A beta associated proteins in the cerebral neocortex, in the cerebellar cortex where A beta plaques are mainly of the diffuse type, and also in the cerebral neocortex of non-demented patients with A beta plaques. Results show that immunolabeling for C1q, C4c, C3d, alpha 1-ACT and Apolipoprotein E (ApoE) occurs in the great majority of A beta plaques in all groups. ApoJ is present in A beta plaques of the cerebral neocortex in AD and in non-demented elderly, but is almost absent from those of the AD cerebellar cortex. C4Bp and P-component, in contrast to AD, rarely occurs in A beta plaques of the cerebral neocortex in the non-demented elderly. Heparan sulphate proteoglycan (HSPG) core protein and intercellular adhesion molecule-1 (ICAM-1) are absent in the diffuse A beta plaques in the AD cerebellum. These differences in distribution and expression of A beta associated proteins may be determined by brain region specific factors (cerebral cortex versus cerebellar cortex) and clinical state (demented versus non-demented cases). We suggest that, besides A beta peptide, certain A beta associated proteins are required for both amyloid plaque formation and for the induction of neurofibrillary changes.