In vivo CTL cytotoxicity against GP33-41-coated cells in B6 mice and OM → RAG1^-/- chimeras after immunization with DCs. Mice were immunized with 1 to 2 × 10⁶ splenic DCs coated with GP33-41 peptide on days 0 and 14. GP33-41–specific cytotoxicity in vivo was assessed on day 21. Splenic cells pulsed with 10^-6 M GP33-41 peptide or not were labeled with a high (250 nM) and low (25 nM) concentration of CFSE, respectively. A 1:1 mixture of these target cell populations was injected intravenously into naive and immunized mice. After 4 hours, the mice were killed and the spleen and mLNs were analyzed for the presence of CFSE^high and CFSE^low target cell populations and the tetramer-positive CD8 T cells. (A) Data show a representative histogram plot of spleen cells from naive and immunized mice 4 hours after transfer of CFSE-labeled target cells. (B) Percentage (mean ± SD) of specific lysis in spleen and mLNs of immunized B6 mice (□) and chimeras (▪). The mean numbers of GP33-specific CD8 cells are shown above each bar. There were 3 mice per group.