HAGEMAN-FACTOR AND ITS BINDING-SITES ARE PRESENT IN SENILE PLAQUES OFALZHEIMERS-DISEASE

Hageman factor (HF) or factor XII participates in several defense syst ems of the body. These include coagulation, fibrinolysis and complemen t activation. We investigated the expression of HF and its mRNA in con trol and Alzheimer's disease (AD) brain, using immunohistochemistry an d polymerase-chain reaction (PCR) techniques. HF mRNA was detected in control and AD brain extracts, indicating that HF can be produced by e ndogenous brain cells. HF-like immunoreactivity was present in residua l serum of capillaries in both control and AD brain, consistent with i ts known presence in the circulation. In addition, AD senile plaques w ere stained. The staining was dramatically enhanced when AD sections w ere incubated with solutions containing HF, indicating that plaques co ntain not only HF but also binding sites for HF. The enhanced staining was eliminated by pretreatment of solutions with the HF-binding agent kaolin. It was also eliminated by pretreatment of sections with prota mine, an agent which strongly binds to negative surfaces. These data s uggest that negatively charged surfaces in plaques might bind HF in vi vo. Since HF can be activated by contact with negative surfaces, local ly released HF could be playing a role in initiating a variety of infl ammatory responses in AD brain.