Fig. 2

IL-9 is expressed in gray matter lesions and meninges of secondary progressive MS patients. Neuropathological analysis of IL-9 expression in post-mortem MS gray matter and meninges by immunohistochemistry and immunofluorescence. In normal appearing gray matter (NAGM) (a), rare IL-9⁺ cells with microglia morphology were detected (b). In active gray matter lesions (GML) (c), in areas containing MHC class II⁺ cells with microglia morphology (d), scattered IL-9⁺ were present (e, f), in particular in the external cortical layers close to the CSF surface or around small blood vessels. High numbers of IL-9⁺ cells (h) were observed in meningeal infiltrates (g) overlying the cortical gray matter. Double immunofluorescence for CD4 and IL-9 (i) or CD8 and IL-9 (j) of meningeal infiltrates in post-mortem brain tissues of progressive MS patients demonstrated that CD4⁺ (arrowheads in i), but not CD8⁺, T lymphocytes express IL-9. Original magnifications: × 100 (a, c, d), × 200 (b, g, h), × 400 (e, f, i, j)