A , Representative images from 18-month-old PDAPP/TRE mice double stained with anti-apoE (apoE, green) or anti-Aβ (Aβ, red) and merged (yellow). B , Quantification of apoE and Aβ colocalization in PDAPP/TRE brain sections. The vast majority (∼90%) the apoE signal that is measured in the brain from PDAPP/TRE4 mice is associated with Aβ, whereas only ∼25% of apoE and Aβ are colocalized in very old PDAPP/TRE2 mice. ***p < 0.001 versus all other groups, ANOVA, Tukey–Kramer post test.