Early complement activation increases in the brain in some aged normal subjects

Complement activation is increased in Alzheimer’s disease (AD) and may contribute to the development and progression of this disorder. To compare early complement activation between normal and AD brain specimens, C4d and iC3b concentrations were measured in hippocampus, entorhinal cortex, temporal cortex, parietal cortex, and cerebellum from aged normal and AD subjects ( n=10–14 for both), and in hippocampus and entorhinal cortex from younger normal subjects ( n=5–6). C4d and iC3b levels increased 2.3- to 4.6-fold in AD versus aged normal specimens (all P