Figure 7

Histological correlations. The tissue distribution of fluorescence-labeled Gf was histologically assessed at two time points, 24 h (A and B) and 72 h (C) after intravenous Gf injection, and correlated to MRI. Coronal T1-weighted MR images 24 h after Gf injection are shown. Gf-enhancing lesions are marked by squares (A1 and B1). Two exemplary lesions studied after 24 h are shown, one with a periventricular inflammatory focus close to the corpus callosum (A) and a second spreading from the hippocampal fimbria to the choroid plexus (*) (B). Corresponding H&E stained (A2 and B2) and fluorescence microscopy (A3, B3, B4; red: Gf, blue: Hoechst 33258) slices depict typical inflammatory plaques, including cellular infiltrations (arrows), halo-like surrounded by Gf. A detail is given in higher magnification to point out the diffusely extracellular accumulation of Gf (B4). After 72 h, Gf uptake into macrophages/microglia was evident. In the choroid plexus, internalized Gf became visible in numerous IBA-1 positive cells (arrows in C; red: Gf; green: IBA-1; blue: Hoechst 33258). The MR image is shown to localize the detail (C: arrowhead).