OSE-Itga4^ΔB mice fail to build up MEBAGs in the spinal cord meningeal compartment and show a pronounced disease burden. Spontaneous EAE was monitored in littermate control mice (OSE; TCR^MOG; BCR^{MOG, KI/KI}; Itga4^flox/flox, n = 68) and B cell-conditional α4 integrin deficient OSE mice (OSE-Itga4^ΔB; TCR^MOG; BCR^{MOG, KI/KI}; Itga4^flox/flox, Cd19-Cre^wt/KI, n = 76). (A) Incidence of EAE in OSE and OSE-Itga4^ΔB mice. (B) EAE score including AUC, Student’s t-test. (C) Mortality of OSE and OSE-Itga4^ΔB mice; Mantel-Cox log-rank test. (D) In some animals, spleen and spinal cord sections were analysed for B cells by staining with B220 at around 4 weeks after onset of disease. Representative sections for OSE control or OSE-Itga4^ΔB mice, respectively. Scale bars = 200 µm and 50 µm. (E) The MEBAG area was assessed as fraction of the transversal white matter area at the respective spinal cord level. Symbols indicate individual sections. In each group six mice were included in the analysis, and the three sections of each mouse with the largest MEBAGs were analysed; unpaired Student’s t-test. (F) Spinal cord sections of OSE control mice or OSE-Itga4^ΔB mice were prepared 4 weeks after onset of disease and stained for T cells (CD3) and macrophages (Mac-3). The amount of demyelination was assessed by LFB-PAS (demyelinated area limited by dashed line). Scale bars = 200 µm and 50 µm. (G) The macrophage infiltrate in the spinal cord parenchyma was quantified in littermate control mice and OSE-Itga4^ΔB mice by assessing the fraction of the spinal cord parenchyma (excluding meninges) that displayed a Mac-3 signal. Individual mice from the two groups were paired, and the spinal cord sections with the largest Mac-3 infiltrates from three mice in each group were analysed. Bars represent means; t-test.