Figure 2.

Histological examination of cerebral cortex sites with foci of attenuated MRI signal (α, β, γ). At 24 h following SPIO administration, a male 28-month-old APP23 mouse was analyzed in vivo by MRI and processed for histology immediately thereafter. Perls/Prussian blue staining showed iron-loaded macrophages in CAA-laden vessels (Congo red positive) at both sites (α and β). While the vessel walls were thickened at both α and β locations, only site β in addition showed vasculitis characterized by lymphocyte infiltration (Hematoxylin eosin). At site γ, isolated iron-loaded macrophages (severity grade 1) were present close to amyloid vessels. 1, Iron in isolated macrophages; 2, iron in macrophages at the vessel wall; 3, amyloid deposit in vessel wall; 4, vasculitis; P, amyloid plaque. Scale bars, 50 μm. Congo red-stained sections were observed under bright field or polarized light.