Fig. 4

IL-1β expression in different types of MS lesions. MS lesions in frozen 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). IL-1β expression (in brown, right panels) was mainly observed in ramified MHC class II⁺ cells in the parenchyma, which were mainly localized at the edges of active lesions. Chronic active lesions were classified by the presence of a completely demyelinated (PLP⁻) center surrounded by a rim of MHC class II⁺ cells (b). IL-1β expression was observed in MHC class II⁺ cells in the rim of the lesion. Again, we observed MHC class II⁺ microglia nodules in otherwise NAWM (c) in which IL-1β was expressed. Original magnifications ×10, insets ×40 (a–c), scale bar represents 200 μm