Fig. 4

Inflammatory changes. Microglial nodules and neuronophagia. a, b H&E-stained sections of medulla oblongata at the inferior olivary nucleus (a) and cerebellar dentate nucleus (b) show neuronophagia (arrow). c H&E-stained section of medulla oblongata shows a microglial nodule (arrow). d Immunohistochemistry against HLA-DP, DQ, and DR antibody shows clustered microglia in the nodule. e Immunohistochemistry against CD8 antibody shows CD8 + T cell accumulation within an area of the microglial nodule. f CD8 immunostaining identifies lymphocytic cuffing in the medulla oblongata. Microglial activation. g-l Immunostaining with HLA-DP DQ DR shows mild (g, j), moderate (h, k), and severe (I, l) microglial activation from medulla (g–i) and olfactory bulb (j–l). Lymphocytic inflammation. m Immunostaining with CD4 shows moderate CD4 + T cell accumulation (arrows) in the meninges. n, o Immunostaining with CD8 presents moderate CD8 + T cell accumulation (arrows) around the vessel (n) and in the parenchyma (o). Acute hemorrhagic leukoencephalitis. p The medial left hemisphere shows multiple petechiae (arrows) throughout the brain including the corpus callosum, primarily in the genu and splenium. q H&E stained corpus callosum shows gross acute intraparenchymal hemorrhage. r H&E section of the temporal white matter shows necrotic vessel with hemorrhage “ball ring pattern” (arrow) with hemosiderin-laden macrophages, consistent with acute hemorrhagic leukoencephalitis. s Luxol-fast blue/H&E stain section demonstrates the perivascular myelin loss (arrow) within the lesion. t Immunohistochemistry with neurofilament (NF-31) antibody identifies some damaged axons (arrow) within an area of myelin loss. Cerebral vasculitis-like changes. u H&E section of cerebellar white matter shows vasculitis-related changes (fibrinoid necrosis, disruption of the vessel wall with inflammatory reactions). v, w Immunostaining with CD68 and CD8 shows activated microglial cells and macrophages (arrow, v) and T cells (arrow, w) around the vessel wall. x Immunostaining with fibrin antibody represents fibrin deposition (arrow) within the vessel wall. Scale bar: 1 mm (p), 200 µm (q–x), 100 µm (c–e and g–o), and 50 µm (a, b, and f)