(A) Immunofluorescence analysis of the old APPPS1 slice (14 DIV) treated with GM-CSF and vehicle Ctr and immunostained with CD68 (red), cell proliferation marker Ki67 (green) and M3.2 (blue). Scale bar: 50 µm.(B) Quantitative analysis of Ki67 and CD68 double positive microglial cells in the old APPPS1 tissue (14 DIV) treated with GM-CSF and Ctr reveals increased microglial proliferation upon treatment with GM-CSF. The values are expressed as percentages of CD68 and Ki67 double positive microglial cells from the total number of CD68 positive cells and represent mean ± SEM from 2 independent experiments, each experiment including 4 independent slice culture dishes (***P < 0.001). 