COLOCALIZATION OF BETA A4 AND CYSTATIN-C IN CORTICAL BLOOD-VESSELS INDUTCH, BUT NOT IN ICELANDIC HEREDITARY CEREBRAL-HEMORRHAGE WITH AMYLOIDOSIS/

Based on the recent discovery of co-localization of beta/A4 and cystat in C in cortical blood vessels of patients with cerebral hemorrhages d ue to sporadic amyloid angiopathy and patients with Alzheimer's diseas e we investigated the presence of these two proteins in the cortical b lood vessels of patients suffering from hereditary cerebral hemorrhage with amyloidosis of the Dutch (n = 11) and the Icelandic (n = 2) type . The brains of three patients with sporadic cerebral amyloid angiopat hy were also investigated. Blood vessels of the Dutch patients clearly showed immunostaining with beta/A4 as well as with cystatin C antibod ies, whereas the blood vessels of Icelandic patients showed only stain ing with cystatin C. In one of the three sporadic amyloid angiopathy p atients co-localization was shown as well. The co-localization of muta ted beta/A4 with normal cystatin C in the Dutch patients suggests that cystatin C deposition occurs secondarily to beta/A4 deposition. This is probably also the case in sporadic amyloid angiopathy and Alzheimer 's disease. Cystatin C deposition may play a role in the development o f cerebral hemorrhages and leukoencephalopathy.