Fig. 3

IL-1β expression in different types of MS lesions. MS lesions in paraffin-embedded brain tissue sections were characterized based on the extent of myelin (PLP in brown, left panels) damage and activation of innate immune cells (MHC class II in brown, middle panels). Active MS lesions were classified as areas with ongoing demyelination and activation of MHC class II⁺ innate immune cells (a). Chronic active lesions were classified by the presence of a completely demyelinated (PLP⁻) center surrounded by a rim of MHC class II⁺ cells (b). Inactive lesions were classified by the presence of demyelinated areas where the immune response has resided (c). We did not detect IL-1β (in brown, right panels) in active, chronic active, and inactive MS lesions in paraffin-embedded tissue sections (a–c). In addition, we observed MHC class II⁺ microglia nodules in otherwise NAWM (d) in which IL-1β was expressed. Double labeling of these microglia nodules for IL-1β (in red) and Iba-1 (in green) implicated that all IL-1β⁺ cells were Iba-1⁺ (e). Original magnifications ×4, insets ×100 (a–d), scale bar represents 500 μm (a–d) or 10 μm (e). Nuclei were counterstained with hematoxylin (blue; a–d)