Ly-6C⁺ monocytes migrate to the CNS during EAE and up-regulate CD11c and MHC class II. Mice were treated with clodronate or PBS liposomes 24 hours after transfer of encephalitogenic T cells. Eighteen hours after liposome treatment, animals were injected with FITC-labeled microspheres. (A) Left: Expression of FITC and CD11b by CD115⁺-gated cells 5 days after liposome treatment and 4 days after FITC microsphere injection. Right: Ly-6C expression on FITC⁺CD115⁺ blood monocytes from clodronate versus PBS liposome-treated animals. Histograms are based on cells that fall within the R1 gate (left panel). (B) Spinal cord mononuclear cells were harvested from mice treated with clodronate (left) or PBS liposome (right) during peak EAE and analyzed for FITC expression. (C) The cell surface phenotype of CNS-infiltrating FITC⁺ cells (shown in the gate of panel B left) was determined by FACS. (D) CD11b⁺MHC class II⁺Ly-6C⁺ cells were sorted from the blood and CNS of mice with EAE and analyzed by real-time RT-PCR for the genes shown. The data are shown as fold expression in CNS-infiltrating cells over circulating cells. (A-D) All experiments shown were repeated 3 times with similar results. *P < .05, comparing mRNA levels in CNS versus blood Ly-6C⁺ monocytes.