α₁-Antichymotrypsin gene polymorphism and risk for Alzheimer's disease

α₁-Antichymotrypsin (ACT), a component of the senile plaque of the Alzheimer's disese (AD) brain, has a possible role as a molecular chaperone in developing AD pathology. This study was a search for the possible association of the two structural polymorphisms of ACT, Ala¹⁵ → Thr and Met³⁸⁹ → Val in the Japanese population. In 101 AD patients, genotype and allele frequencies of the two polymorphisms did not differ from those of 104 age-matched healthy controls. However, in those subjects in which the apolipoprotein ε4 allele was absent, the frequency of the Ala¹⁵ homozygote was significantly higher in the AD patients than in controls. This suggests that the Ala¹⁵ homozygote state may be a susceptibility marker for AD, interacting with apolipoprotein E genotype.