(H) Representative immunofluorescence images of Iba1 (green) and APOE (red) on cortical sections from SPF and GF mice. Nuclei were stained with DAPI (blue). Scale bar: 50 μm. White arrowheads indicate APOE+/Iba1+ microglia and arrows show APOE-/Iba1+ microglia. Quantification of APOE+/Iba1+ microglia. Each symbol represents one mouse. At least three slides were examined per individual mouse. Data are presented as mean ± s.e.m. Significant differences were determined by unpaired t-test and marked with asterisks (*P < 0.05). Data are representative of two independent experiments. 