Serum amyloid P component level in Alzheimer's disease

Serum amyloid P component (AP) is a normal plasma constituent that is observed in senile plaques and neurofibrillary tangles in brains of Alzheimer's disease (AD) patients. In this study we have evaluated the AP levels in sera of 16 patients with AD and in 16 control subjects by enzyme-linked immunosorbent assay. The AP level was 22.4 +/- (SD) 7.0 micrograms/ml in the AD group and 34.4 +/- (SD) 6.6 micrograms/ml in the control group. The AP level in the AD group was significantly lower than that of the control group (p < 0.01). In the control group, there was no correlation between AP levels and age. Our results suggest that the production of AP by the liver (hepatocytes), thought to be the only source, may be suppressed in AD patients and that the deposition of AP in senile plaques and neurofibrillary tangles is not due to its overproduction.