Figure 1.

Pathology of human and experimental neurodegenerative disorders showing involvement of the immune response. (a) Toll-like receptor 3 (TLR3) expression in neurons in multiple sclerosis (MS). The insert shows the granular appearance of the receptor in the cytoplasm (arrow). (b) Activated microglia, as depicted by human leucocyte antigen (HLA) class II expression (blue) around amyloid-beta (Aβ)-positive accumulations (red) inside neurons in Alzheimer’s disease. (c) HLA class II expression by activated microglia (blue) phagocytosing myelin basic protein (red) in stroke. (d) Lipid-laden (oil red O positive) foamy macrophages (blue) in an active MS lesion. (e) HLA class II-positive microglia (brown) at the edge of a chronic active lesion in MS. Activated microglia/macrophages surrounding a blood vessel in the lesion (arrow). (f) CD45⁺ lymphocytes (arrow) and (g) CD20⁺ B cells (brown) in perivascular infiltrates in MS. (h) HLA class II-positive microglia (blue) close to a damage axon red (arrow) stained for neurofilament light (NF-L). (i) Meningeal infiltrate in acute bacterial meningitis containing a single CD20⁺ cell (brown). The majority of cells are polymorphonuclear cells (inset). (j, k) Shrunken and swollen axons (arrows) in the spinal cord of mice with experimentally induced neuronal damage following immunization with NF-L. In the same mice, CD3⁺ T cells (l), and (m) B cells in the meninges close to areas of neuronal degeneration, are shown.