Cervical lymph node targeting of CSF-injected DCs. Bone marrow-derived DCs were labeled with CFSE then injected into the CSF (A-D) or brain parenchyma (E-F) of normal rats. Histologic examination of cervical or axillary lymph nodes was performed by fluorescence microscopy after counterstaining with DAPI for nuclei visualization (blue). Photomicrographs show representative results obtained from analyzing lymph nodes on day 3 after injection. (A-B) In the cervical lymph nodes, numerous labeled cells are detected within B-cell cortical follicles (A) and in the medulla (B). (C-D) Only occasional labeled cells are detected in axillary lymph nodes and are mainly localized in the medulla. (E-F) Following injections of DCs into brain parenchyma, no labeled cells are observed in cervical (E) or axillary lymph nodes (F). Scale bars: 200 μm.