Figure 2.

Immune responses in human and experimental inflammatory neurodegenerative disorders. B‐cells (arrows) are observed in white (a) and grey matter lesions (b) in multiple sclerosis (MS). (c) and (d) depict an MS leucocortical lesion. The white matter (WML) is associated with HLA ⁺ microglia (d, WML) in contrast to the lack of HLA ⁺ microglia in the grey matter (d, GML). A similar pattern of HLA ⁺ cells is seen in the white and grey matter in an X‐ALD case (e) and where peripheral macrophages infiltrate the white matter (f). Granulocytes (arrow) in suspected vasculitis cases (g). Ageing influences the activity of microglia in a mouse model of MS: microglia in the central nervous system (CNS) of young mice (h; Iba1 staining) are less active than in aged mice (i). In MS cases microglia in normal appearing white matter express P2Y12 (j) and TMEM119 (k). In progressive multifocal leucoencephalopathy astrocytes (l, arrow) and activated microglia/macrophages (m, arrow) are highly reactive in an area of demyelination. The paucity of astrocytic glial fibrillary acidic protein expression (red circle, n) is associated with an area of microglial activation (red circle, o) in acute haemorrhagic leucoencephalitis.