Histological findings. EAE-typical perivascular cell infiltrations were identified on Hematoxylin & Eosin stained slices (A). After Prussian Blue staining, VSOP was detected on corresponding sites (B). Two different distribution patterns of magnetic nanoparticles became evident: The incorporation of VSOP into cytoplasmatic vesicles within phagocytic cells (arrows in C), and a diffuse accumulation in the brain parenchyma (ellipse in D). IBA-1 positive macrophages/microglia were identified by immunofluorescent staining within perivascular plaques, colocalizing with Prussian Blue positive cells (arrows in E, and in higher magnification in F; green: anti-IBA-1, macrophages/microglia; blue: Hoechst 33258, cell nuclei; red: rhodamin phalloidin, vascular structures).