Formation and maintenance of β-amyloid plaques in the absence of microglia

Background: In Alzheimer's disease β-amyloid plaque deposits are accompanied by an inflammatory reaction involving microglia, which are the primary phagocytotic immune cells of the brain. Microglia cells are attracted to and surround amyloid plaques, suggesting a role in plaque formation and/or restricting unlimited plaque growth. Methods: Amyloid precursor protein transgenic mouse models (APPPS1 and APP23) have been crossed with CD11b-HSVTK transgenic mice. Results: These mice allow 30% and >90% microglia depletion upon systemic and intracerebroventricular ganciclovir application, respectively, for up to 4 weeks. Conclusions: Opposite to expectations, results show that amyloid plaque formation can occur in the absence of microglia and that microglia depletion in amyloid-bearing mice does not influence amyloid plaque load.