(A–J and L–O) The optic nerves (A–F) and spinal cords (G–J and L–O) from OSE mice that developed neurological disease in a non-SPF environment showed severe infiltration, demyelination, and axonal damage as visualized by H&E (A, D, G, and I), luxol fast blue (B, E, H, and J), and Bielschowsky silver impregnation (C and F). Arrows in G indicate eosinophilic granulocytes. (K) Demyelinating lesions (red shading) were specifically localized in the optic nerves and spinal cords of OSE mice, thus resembling the lesion distribution observed in human Devic disease. Cervical sections are labeled C1–C8; thoracic sections are labeled T1–T13; lumbar sections of the spinal cord are labeled L1–L7. (L–O) Cellular infiltrates were predominantly composed of CD11b⁺ macrophages/microglia (L) and CD4⁺ T cells (M), while only few CD8⁺ T (N) and B cells (O) were found exclusively in the optic nerves and spinal cords of sick mice. Note that healthy OSE littermates remained free of demyelinating CNS lesions (see Supplemental Figure 3). Furthermore, OSE mice housed under SPF conditions showed slightly stronger infiltration/demyelination (see Supplemental Figure 4).