Histological staining for infiltrating cells in P2x7 and WT mice. Serial sections were prepared from EAE immunized P2x7 null and WT mice at day 21 after immunization. At this time, the 3 WT mice had clinical scores of 2.0; and the 3 P2x7 null mice had no clinical signs. Sections were stained with H&E to detect the presence of infiltrating cells. Representative sections from the cerebellum show the presence of perivascular infiltrating cells (arrows) in the cerebellar white matter of both P2x7 (A) and WT (B) brains. Sections taken from near the IVth ventricle show the presence of infiltrating cells (arrows) beneath the corpus callosum and lining the ventricle in both P2x7 (C) and WT (D) brains. (E) Quantitation of the average total number of infiltrating cells (mean ± sd) measured in 4 serial sections for P2x7 and WT mice (n = 3 mice each).