TLR4 mutation did not influence Aβ load but diminished microglial activation in an AD mouse model at 5 months of age. Aβ deposits in the brains of TLR4W Tg (A) and TLR4M Tg (B) mice were visualized by anti-Aβ antibody (6E10). Activated microglia are visualized by anti-CD11b antibody in TLR4W Tg (C) and TLR4M Tg (D) mice. The inset image (C) is a higher magnification of the area indicated by the square. (E) Cerebral Aβ plaques are visualized by 6E10 and average percentages of Aβ-immunoreactive areas in the cerebral cortex are shown as a bar graph (means ± SEM). Average percentages of immunoreactive areas in the cerebral cortex for an activated microglial marker, CD11b (F), are shown as a bar graph (means ± SEM). The ratio of CD11b-immunoreactive area to 6E10-immunoreactive area in the cerebral cortex (G) are shown as a bar graph (means ± SEM). Brain sections from 5-month-old TLR4W Tg (H) and TLR4M Tg (I) mice were subjected to double-label fluorescence immunohistochemistry using anti-CD11b (green) antibody and 6E10 (red). *P ≤ 0.05. Scale bars 200 μm for A through D, 50 μm for H and I, and 10 μm for the inset.