H&E staining reveals an extensive mononuclear cell infiltration in spinal cord of (B6 × SJL) F1 (H-2b/s) relapsing mice (top panel). In these mice inflammatory cells are evident throughout the spinal cord parenchyma. Lesser degree of inflammation was observed in relapsing B6 (H-2b) mice (lower panel). Representative image shows lumbar spinal cord from relapsing H-2b/s mouse, with clinical severity score of 3, and relapsing H-2b mouse with severity score of 2. (H&E × 10).