Figure 3.

MHCII-Knockout 5XFAD Mice Exhibit An Exacerbated Amyloid Pathology

Immune-deficient 5XFAD mice lacking MHCII (5XFAD/MHCII^−/−) were generated, and their plaque pathology, neuroinflammation, and phagocytic clearance were characterized. 5XFAD/MHCII^−/− and age-matched 5XFAD mice (n = 4–5 mice per group) were killed at 1, 3, or 6 months of age, and their brain samples were analyzed by IHC or qPCR.

(A) A breeding diagram of the strategy used to generate 5XFAD/MHCII^−/− mice.

(B) Representative IHC images showing Aβ plaque pathology at 1, 3, and 6 months of age in brain sections derived from 5XFAD and 5XFAD/MHCII^−/− mice and immunolabeled for anti-Aβ (red) and a DAPI nucleus counterstain (blue). Quantitative analyses of the Aβ plaque load per volume of cortical section (right graphs) were performed with IMARIS. Each symbol represents one mouse, and the bars represent means ± SEM.

(C) A qPCR analysis of the pro-inflammatory cytokines IL-1β, IL-6, and IFN-γ and the astrogliosis marker GFAP in the brains of 3- (top panels) and 6-month-old (bottom panels) 5XFAD mice, 5XFAD/MHCII^−/− mice, and littermate control mice. Bars represent means ± SEM.

(D) The 3D reconstructions (left images) of z-sections (21 μm overall, 0.75 μm/slice) in cortical sections. The images to the right are higher magnifications of the framed areas, showing the co-localization of Aβ with Iba1+ cells (unsliced and sliced) in brain sections of 5XFAD (top panels) and 5XFAD/MHCII^−/− (bottom panels) mice. Scale bars, 30 μm (left images) and 5 μm (all other images). The quantitative analysis (right graph) of the percentage of Aβ co-localized with Iba1+ microglia in the cortex was performed with IMARIS. Bars represent means ± SEM.

(E) A qPCR analysis of the phagocytic markers TREM2 and SIRP-1β in the cortex of 3- and 6-month-old mice. Bars represent means ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001 ((B and D) Student's t test, (C and E) one-way ANOVA).