(A) Control (SIRPα-flox:— (Ctrl)) or SIRPα cKO (SIRPα-flox:Cx3cr1-CreERT2 (cKO)) mice at 19–30 wks of age were fed a 0.2% (w/w) cuprizone (Cpz) diet. After 3 or 5 wks of Cpz feeding (Cpz 3 wks, Cpz 5 wks), brain samples were prepared. Other groups of mice were returned to a normal diet after 5 wks of Cpz treatment and allowed to recover for 2 wks prior to the tissue analysis (Rec 2 wks). Mice fed a normal diet without Cpz for 3 or 7 wks were analysed as controls (Basal). Brain sections were subjected to immunofluorescence staining with specific antibodies for MBP, Iba1 (red), CD11c (green), and Olig2 (white). Arrowheads and arrows indicate typical demyelination (MBP) or microgliosis (dense immunoreactivity for Iba1) in the corpus callosum (arrowheads) and hippocampal alveus (arrows). Asterisks indicate abnormally strong immunoreactivity of MBP at Cpz 3 wks. Scale bars: 500 μm for MBP, Iba1, and CD11c; 100 μm for Olig2. (B, C, D) Ratio of demyelination area to the white matter (WM) area (including corpus callosum and hippocampal alveus) in the analysed image at Cpz 5 wks (B), or the ratio of the Iba1-positive (C) or CD11c-positive (D) area to the WM area at Basal, Cpz 3–5 wks, and Rec 2 wks, were quantified by the immunoreactivity of MBP, Iba1, and CD11c, respectively. Data are the means ± SEM. A total of eight images obtained from four mice (0 — Basal; 3 — Cpz 3 wks; 5 — Cpz 5 wks), or a total of four images obtained from two mice (5 + 2 — Rec 2 wks) were analysed at each time point for each genotype. *p<0.05, ∆p=0.06 (Welch’s t-test). (E) The number of Olig2+ oligodendrocytes were quantified in the WM area in the analysed image. Data are the means ± SEM. A total of 12–16 images obtained from four mice (0 — Basal; 3 — Cpz 3 wks; 5 — Cpz 5 wks), or a total of eight images obtained from two mice (5 + 2 — Rec 2 wks), were analysed for each genotype. §§§p<0.005 for Ctrl mice, †††p<0.005 for cKO mice (Welch’s t-test) versus the basal value for the respective genotypes. No statistical difference was found between the two genotypes. Filled and open bars or circles in panels (B, C, D, E) indicate control and SIRPα cKO mice, respectively.