Fig. 6

IL-1β expression in perivascular infiltrates in active MS lesions. Within the active lesions of two patients, we observed perivascular infiltrates in areas with ongoing demyelination (PLP, in brown; a). These perivascular cells were strongly MHC class II⁺ (in brown; b). We observed IL-1β expression (in brown) in cells associated with these perivascular infiltrates, mainly at the edges of the infiltrate and the parenchyma (c). These cells were double stained for IL-1β (in brown) and cell surface markers associated with pro-inflammatory or anti-inflammatory cellular phenotypes (in red). IL-1β staining colocalized with MHC class II (d) and CD74, although we also observed multiple IL-1β⁺/CD74⁻ cells (e). Furthermore, IL-1β staining colocalized with CD40 (f), CD200R (g), and CCL22, although we also observed some IL-1β⁺/CCL22⁻ cells (h). IL-1β and MR staining were both observed in the same perivascular infiltrates, but all IL-1β⁺ cells were MR⁻ (i). In addition, within one active lesion, we observed MHC class II⁺ cells (in red) with a foamy appearance (j). These MHC class II⁺ foamy cells did not express detectable levels of IL-1β. In addition, we observed some IL-1β staining (in brown) in reactive astrocytes in the same active lesion (k). Original magnifications ×40, scale bar represents 50 μm. Nuclei were counterstained with hematoxylin (blue)