Several studies suggest that systemic infection occurring during aging and chronic neurodegenerative diseases can evoke an exaggerated immune response that contributes to the progression of neurodegeneration and cognitive decline. However, studies directly addressing the relationship between microbial environment and the onset of neurodegeneration in Alzheimer’s disease animal models are lacking. Here we showthat the onset of neurodegeneration that transgenic mice develop when raised in conventional husbandry slows down when raising anti-nerve growth factor transgenic mice in a murine pathogen free condition.