Elevated alpha 1-antichymotrypsin serum levels in a subset of nondemented first-degree relatives of Alzheimer's disease patients.

A portion of Alzheimer's disease (AD) patients have elevated serum levels of the acute phase reactant alpha 1-antichymotrypsin (A1ACT) compared to age-matched controls. We measured serum levels of A1ACT in AD patients, age-matched controls, Down's syndrome patients, and nondemented first-degree relatives of AD patients. Significantly elevated levels of A1ACT were found in both AD patients and first-degree-relatives. In AD patients, serum A1ACT concentrations decreased with increasing severity of cognitive impairment. These results may suggest that inflammatory phenomena may be an early component of AD pathophysiology.