Serum Amyloid P Immunoreactivity in Cortical Tangles, Plaques and Vessels in Alzheimer’s Disease: Implications for Dysfunction of the Blood-Brain Barrier?

Abstract

Amyloid P component (AP) is an α ₁-glycoprotein found in almost all types of amyloid deposits, representing 10–20% of the weight of the amyloid fibrils^l. AP is a normal constituent of serum (SAP) synthesized by the liver, the only tissue that appears to exhibit its mRNA². Investigators have previously attempted to demonstrate the immunocytochemical localization of SAP in brain amyloid deposits of subjects with Alzheimer’s disease (AD). In earlier studies^3–5, positive SAP antigenicity was evident only in cerebral vessels of AD subjects and those of hereditary cerebral hemorrhage with amyloidosis of the Icelandic type^3,6. More recently such immunoreactivity has been demonstrated in senile plaques of AD^5,6, as well as cerebral vessels, and in other related disorders exhibiting cerebral amyloid angiopathy⁶ (CAA). However, with the exception of a recent preliminary report⁷, SAP immunoreactivity has not been, so far, described in neurofibrillary tangles.