Blood concentrations of lipopolysaccharide (LPS) together with inflammatory cytokines, e.g., IL-1β and tumor necrosis factor (TNF)-α, are increased in AD patients compared to non-AD individuals with and without cognitive impairment.29 Components of Porphyromonas gingivalis, a bacterium often existing in chronic periodontitis, were found in the brains of AD patients.30 We have observed that bacterial receptors CD14 and Toll-like receptor (TLR)-2 are receptors for aggregated Aβ,31–33 implying that Aβ and bacterial components share receptors on microglia in the brain. This evidence concerns the gene TLR2 and Alzheimer disease.