Monoclonal antibody 3C11 was found to have an epitope within the N-terminal region of Aβ determined by ELISA, react with APP overexpressed in cultured cells, and immunohistochemically stain parenchymal Aβ plaque and cerebrovascular pathology in the TgCRND8 mouse model of amyloidosis and post-mortem human brain tissue from individuals neuropathologically diagnosed with AD. The gene discussed is APP; the disease is amyloidosis.