CEREBROSPINAL-FLUID C3A INCREASES WITH AGE, BUT DOES NOT INCREASE FURTHER IN ALZHEIMERS-DISEASE

Complement activation is present in the brain in Alzheimer's disease ( AD), and Clq concentrations are decreased in AD cerebrospinal fluid (C SF). To determine whether concentrations of other complement proteins are also altered in AD CSF, we measured concentrations of C3a and SC5b -9 in CSF from patients with probable AD (n = 19), normal aged control s (n = 11), and normal younger controls (n = 15). C3a concentrations w ere similar between AD and aged controls, but threefold higher than in younger controls (p < 0.05 vs. both groups). A similar pattern was fo und with SC5b-9, though the increase was only twofold and statisticall y significant only for AD vs. younger controls. These results suggest that an increased generation of complement proteins in localized areas of the AD brain does not result in elevated concentrations of these p roteins in CSF, compared with age-matched controls. Increased C3a (and , to a lesser extent, SC5b-9) in aged controls may be due to increased complement activation, increased central nervous system production, a nd/or blood-brain barrier leakage of these proteins. (C) 1997 Elsevier Science Inc.