Detection of inflammatory cells and MHC class II expression in the CNS. Brains were obtained from EAE mice at the peak of clinical EAE (day 21 pi, top row), and naïve mice (bottom row). (A and H) Hematoxylin and eosin (H&E) staining of an inflammatory perivascular focus in CNS. Confocal images of IF staining (green) for (B and I) CD4+ T cells; (C and J) CD11c+ dendritic cells; (D and K) CD11b+ microglia/infiltrating macrophages; (E and L) Ly-6G+ neutrophils; (F and M) CD19+ B cells; and (G and N) MHC II+ cells. Cell nuclei are stained with DAPI. As expected, only microglia were present in significant numbers in the naïve parenchyma (K), whereas other cell types were found only in meninges prior to immunization (I, J and L). (F and M) CD19+ B cells were not detected in the CNS of naïve or EAE mice. (G and N) IF staining for MHC class II molecule shows increased expression during EAE while expression is low in the naïve brain.