Figure 4. CSF-circulating DCs migrate along the deep penetrating meninges.

Fluorescent microspheres or DCs labeled with the cytoplasmic fluorescent marker CFSE were injected into the left lateral ventricle of EAE rats (n = 32) at the clinical peak of disease (day 12 post-immunization). EAE rats injected with fluorescent microspheres (n = 14) or CFSE-labeled DCs (n = 18) were then sacrificed on day 1 post-injection (n = 16) and an immunohistological analysis of brains was performed using antibodies directed against CD11b/CD11c (OX42) or MHC class II molecules. Nuclei were counterstained with the fluorescent nuclear dye DAPI. A, B: Counterstaining of nuclei with DAPI coloration (A) shows that microspheres⁺ cells (visualized as white spots in B) localize in the deep penetrating meninges lining the inner parts of the brainstem (Bs) and cerebllum (Cb). C–E: Microspheres⁺ cells (white in D, red in E) expressing MHC class II molecules (green in C and E) are observed in the deep penetrating meninges covering the cerebellar convolutions. Insert in E shows a high magnification view of a ramified microsphere⁺/MHC class II⁺ cell observed in the penetrating pia matter. F, G: Counterstaining of nuclei with DAPI coloration (F) shows that CFSE⁺ cells (G) localize along the pia matter lining the inner parts of the brainstem (Bs) and cerebellum (Cb). H–J: An OX42⁺ infiltrate is observed in the deep penetrating meninges covering the inner parts of the brainstem (Bs) and cerebellum (Cb) (H). These infiltrating cells comprise CFSE⁺ cells (I) that express OX42 (J). Scale bars: 100 µm (F–G), 50 µm (A–E, H–J), 10 µm (insert in panel E).