Acute phase proteins but not activated microglial cells are present in parenchymal β A4 deposits in the brains of patients with hereditary cerebral hemorrhage with amyloidosis-Dutch type

With immunohistochemical staining methods on cryostat sections we investigated the brains of three patients with hereditary cerebral hemorrhage with amyloidosis-Dutch type, one of the cerebral β A4 amyloid diseases. Immunostaining for β A4 protein revealed numerous non-fibrillar β A4 depositions (amorphous or diffuse plaques) in the brain parenchyma in addition to extensive vascular amyloid deposition. All amorphous plaques contain complement proteins and α₁-antichymotrypsin but activated microglial cells expressing major histocompatibility (MHC) class II antigens HLA-DR and leucocyte adhesion molecules belonging to the lymphocyte-function-associated antigen (LFA)-1 family are virtually absent in cortical gray matter. Our findings are discussed from the view that a cascade of events including acute phase proteins and activated microglial cells are involved in classical amyloid plaque formation.