Labeling of spinal perivascular macrophages (SPM) after icv injection of HRP in rats with EAE. A: Spinal cord of a rat with a severe paraparesis showing large erythrocytic infiltrates but no labeling of SPM; 50 μm vibratome section. B: The successful HRP-DAB labeling of SPM (arrows) in rats with EAE reveals more labeled SPM than in normal control animals; 50 μm vibratome section. C: The dense perivascular leukocytic infiltrates in the spinal cord parenchyma of rats with severe paraparesis allow only poor spatial resolution between the endothelial and extravasated cells in 50 μm thick vibratome sections. D: No differentiation among the various types of extravasated cells filling the periavscular space was possible also in plastic semithin sections (0.5 μm thick) counterstained with toluidine blue. E: Rat with severe paraparesis. Electron micrograph showing a HRP-labeled SPM with vacuolated cytoplasm. Counterstaining with uranyl acetate and lead citrate.