Phenotypic analysis of immune cells infiltrating the CSF spaces and the brain parenchyma of rats during EAE. (A, B) CD68+, MPO+ (A), CD3+ (B) and CD45RA+ (B insert, green) cells are shown at D9 in the area of the subfornical organ. CD68+ monocytic cells and CD3+ T cells form the majority of cells in the infiltrates. A significant proportion of MPO+ neutrophils and very few CD45RA+ B cells are also observed. Note the limited number of immune cells associated with the subfornical organ. (C to I) Identification of the cell types infiltrating the brain at D11. The two main populations of immune cells remain CD3+ and CD68+ cells but the proportion of these two cell types vary from cluster to cluster. (C) shows a periventricular parenchymal cell cluster in the forebrain, which is mostly formed by CD3+ cells (D,E). Infiltrating immune cells in the periventricular medulla close to the CP of the fourth ventricle spread along a vessel (F). These cells are monocytes/macrophages (F), as well as CD3+ cells ((G), corresponding to the rectangle in (F)). A large number of CD3+ and CD68+ cells infiltrate the internal CSF cisterns as shown at the level of the ambient cistern (H,I). The number of neutrophils remains very limited in both parenchymal and CSF spaces (E, F, I). Scale bar, 50 μm. Dashed lines delimit ventricles (F) or cisterns (H,I). 4VCP, fourth ventricle choroid plexus; ACi, ambient cistern, fi, fimbria; Hb, habenula; SFO, subfornical organ; VI, velum interpositum cistern.