(A,E,I) Representative light microscopic images of cross-sectioned fimbria, corpus callosum, and prefrontal cortex immunolabeled for amyloid precursor protein (APP) in forebrain PLP cKO and control mice at age 22 months. (B,F,J) Representative light microscopic images of cross-sectioned fimbria, corpus callosum, and prefrontal cortex immunolabeled for MAC3 in forebrain PLP cKO and control mice at age 22 months. (C,G,K) Representative light microscopic images of cross-sectioned fimbria, corpus callosum, and prefrontal cortex immunolabeled for IBA1 in forebrain PLP cKO and control mice at age 22 months. (D,H,L) Representative light microscopic images of cross-sectioned fimbria, corpus callosum, and prefrontal cortex immunolabeled for GFAP in forebrain PLP cKO and control mice. Analyses were performed at 22 months. Genotype-dependent quantifications are shown on the right. Bars represent means ± SEM; datapoints represent individual animals; male and female mice are indicated by squares and triangular datapoints, respectively. Scale bars 50 µm. For statistical analyses two-sided Student’s t-tests were performed for the Ctrl versus cKO comparison. p-Values are given in the bar graphs. All data are shown as means ± SEM. Levels of significance were defined as p>0.05 (*), p>0.01 (**) and p>0.001 (***).