HIGH EXPRESSION ON KUNITZ-TYPE PROTEASE INHIBITOR-CONTAINING SUBSTANCES IN THE CEREBRAL VESSELS OF PATIENTS WITH DOWN-SYNDROME

Down syndrome (DS) brains, from 19 gestational weeks to 50 years of ag e were studied by immunohistochemical methods with a polyclonal antibo dy against synthetic peptide comprising part of the Kunitz-type protea se inhibitor (KPI) domain of Alzheimer disease amyloid precursor prote in (APP), residues 301 to 323 of APP 770. In DS, positive KPI immunore activity was observed in early infancy and from child to adulthood on the tunica media of the arteries in the leptomeninges, cerebral cortex and white matter, but negative or little in controls. In DS with Alzh eimer type dementia, KPI immunoreactivity in the arteries was reduced, but a gross granular reactivity was noted in neurons and glial cells. The high expression of KPI in DS vessels may be one of the predisposi ng factors to vascular diseases and amyloid deposition associated with DS.