Variable deposition of amyloid beta-protein (A beta) with the carboxy-terminus that ends at residue valine(40) (A beta 40) in the cerebral cortex of patients with Alzheimer's disease: A double-labeling immunohistochemical study with antibodies specific for A beta 40 and the A beta that ends at residues alanine(42)/threonine(43) (A beta 42)

Amyloid beta-protein (A beta) deposits in the cerebral cortices of patients with Alzheimer's disease (AD) were investigated immunohistochemically to determine their carboxy terminal sequences. Antibodies specific for A beta terminating at residue valine(40) (A beta 40) and at residues alanine(42)/threonine(43) (A beta 42) were used. Virtually all parenchymal A beta deposits were positive for A beta 42. Many of these deposits were also partially or completely labeled for A beta 40. The degree of A beta 40 labeling varied from area to area within a given brain and from AD case to AD case. In contrast to parenchymal deposits, A beta 40 labeled essentially all the vascular deposits which constitute amyloid angiopathy (AA), with A beta 42 occurring variably in some of these deposits. Occasional AA was found, however, in which A beta 42 predominated or was exclusively deposited. Such a diversity of A beta species, both in brain parenchyma and in AA, suggests that multiple C-terminal processing mechanisms occur in the cell types responsible for these deposits.