Alzheimer's disease (AD) is a typical senile dementia and it is believed that accumulation of Amyloidβ (Aβ) in brain parenchyma is a major cause of the disease. Meanwhile, accumulation of Aβ has been also observed on cerebrovascular walls of nearly 90% of individuals suffering with AD. Aβ is known to be produced from Amyloid Precursor Protein (APP) by cleavage with two types of protease (β- and γ- secretase) and Aβ molecules which accumulate in brain parenchyma are mainly produced from APP expressed in neurons, APP695. In contrast to this, another different APP, APP770, was found to be expressed in cerebrovascular endothelial cells, and it has been newly reported that the Aβ produced from the APP770 can accumulate on cerebrovascular walls (ref. 1). This antibody recognizes human APP770.