Allele frequencies of +874T→A single nucleotide polymorphism at the first intron of IFN-γ gene in Alzheimer's disease patients

Background and aims: Inflammation seems to play a role in progressive neurological degenerative diseases such as Alzheimer's disease (AD). Local inflammatory processes can in fact give rise to direct neurotoxicity, interfere with β-amyloid expression and metabolism, and maintain chronic, intracerebral, acute-phase protein secretion, in turn favoring the formation of β-amyloid fibrils. Accordingly, recent studies show an increased risk for AD associated with certain polymorphisms in the genes encoding some proinflammatory cytokines and acute-phase proteins. To our knowledge, no data have yet been presented on the association between AD and polymorphisms of the interferon(IFN)-γ gene, despite the pivotal role that IFN-γ plays in immune-mediated inflammatory responses. Methods: Using the amplification refractory mutation system method, we evaluated the role of IFN-γ in AD by analyzing, in 111 AD patients and 213 healthy controls, the prevalence of +874T→A single nucleotide polymorphism (SNP), associated with different IFN-γ production. Allele ApoE polymorphisms were assessed by the PCR-based method. Results: No statistically significant differences were observed between AD patients and controls in the frequency of +874 T→A SNP, either on analyzing data as a whole or according to gender. As expected, the frequency of the well-known genetic risk factor APOE-E4 allele was significantly increased in AD patients. However, analyzing the results according to the presence or absence of the APOE-E4 allele, no interactions among ApoE, IFN-γ alleles, gender or age at onset were observed. Conclusions: Our study does not support the hypothesis that IFN-γ SNP may be a genetic risk factor for AD. Further analysis of recently described IFN-γ polymorphisms may clarify the role, if any, of IFN-γ alleles in AD.