Additional file 6: of Microglia prevent peripheral immune cell invasion and promote an anti-inflammatory environment in the brain of APP-PS1 transgenic mice

Figure S6. Iba1+/TMEM119− cells represent a CD68+ macrophage population with peripheral origin highly involved in amyloid-beta phagocytosis. Analysis of CD68 expression in the cortex revealed significantly reduced numbers of Iba1+/TMEM119+/CD68+ cells in APP-PS1 and WT animals upon PLX5622 treatment (A). Surprisingly, higher numbers of Iba1+/TMEM119−/CD68+ cells were found in APP-PS1 animals compared to WT, although these numbers were slightly reduced in APP-PS1 animals by PLX5622 treatment (B). Representative image of CD68 expression in Iba1+/TMEM119− cells located at sites of plaque in APP-PS1 mice (C). Strong MHCII expression was seen sporadically in Iba1+/TMEM119− cells in APP-PS1 mice (D, arrow). Accumulation of CD44 staining (red) was observed extracellularly around amyloid depositions (green) as indicated by the doted ellipse and CD44 staining was seen on Iba1+ cells at sites of plaques (E, insert). Quantification of percentage (%) area of CD44 staining in hippocampal brain regions revealed barely any staining in WT and WT + PLX5622 treated animals, however in APP-PS1 and APP-PS1 + PLX5622 treated mice significantly higher expression of CD44 was observed compared to WT or WT + PLX5622 animals (F). Detailed immunohistochemical analysis revealed increased staining for CD44 at sites of amyloid deposition in areas colonized with Iba1+/TMEM119− cells in APP-PS1 and APP-PS1 PLX5622 treated mice (G, arrow). ThioflavinS was used to stain amyloid plaques and Dapi (blue) was used as nucleus stain. One-way ANOVA with Tukey’s Multiple Comparison Test (A, B, F n = 3/group) was performed. Scale: 50 μm (C, D, E), 20 μm (G). (TIF 4515 kb)