Figure 4. IL-26 treatment reduces fibrinogen and IgG leakage in EAE mice.

(A) Monolayers of mouse BBB ECs immunostained for tight junction molecules JAM-A (red) and claudin-5 (green) and nuclei (blue) after treatment with IFN-γ and TNF-α (I/T), 100 ng/mL IL-26, or left untreated (24 hours treatment). Representative images of n = 4 experiments are shown. JAM-A and Claudin-5 mean fluorescent intensity across the mouse BBB EC membrane was quantified at 30 different places per image. Three fields of view were randomly analyzed and quantified for each condition and for each experiment (n = 240 measurements per condition). Scale bars: 100 μm. (B and C) MOG_35–55 immunized C57BL/6 mice were injected IP with either HBSS or 200 ng recombinant human IL-26 in HBSS daily from day 5 to day 24. Immunohistofluorescence of IgG (green, B, central panel), fibrinogen (green, C, central panel), and PECAM-1 (red, left panel) was performed on spinal cords of EAE mice at day 27 postinduction. Fluorescence of IgG (B, right panel) and fibrinogen (C, right panel) extravasation was quantified (n = 3 animals per group and 3 sections per mouse). Scale bars: 25 μm. Data are represented as mean ± SEM (A–C). *p < 0.05; **p < 0.01; ***p < 0.001. Statistical tests: 1-way analysis of variance followed by the Dunnett multiple comparison test (A) and Student 2-tailed t test (B and C). BBB ECs = blood-brain barrier endothelial cells; EAE = experimental autoimmune encephalomyelitis; HBSS = Hanks balanced salt solution; IL = interleukin; MOG = myelin oligodendrocyte glycoprotein; SEM = standard error of the mean.