Epitope-specific inhibition of B16F1 tumor growth depends on CD8⁺ T cells contained in the transplant graft. (A) CD8⁺ cells were depleted from the grafts used to reconstitute mice that underwent BMT. A representative example of splenic T cells and BM cells after CD8 depletion compared with splenocytes from the same mice before depletion is shown. (B) Mice underwent BMT on day 0. Transplantations were conducted identically to the experiments described in Figure 4A except that CD8⁺ cells were depleted from the spleen and BM cells as shown in 5A. On day 14, 100 000 B16F1 cells were injected subcutaneously. As described in Figure 4, one group received regimens consisting of TRP-2_180-188 + CpG–containing vaccines plus systemic IL-2, and a second group received identical regimens except that the negative control peptide OVA_257-264 replaced TRP-2_180-188. In contrast to the experiments described in Figure 4, no difference in tumor size was observed in the mice that received vaccines containing TRP-2_180-188 compared with the mice that received vaccines containing the negative control peptide OVA_257-264 (TRP-2_180-188 vaccinated, n = 11; OVA_257-264 vaccinated, n = 10). (C) CD8⁺ T-cell depletion persisted 42 days after BMT (28 days after tumor injection) in the mice described in panel B. The plots show splenocytes from a mouse that was reconstituted with a CD8⁺ cell–replete graft and a representative example of splenocytes from a mouse that received a graft that was depleted of CD8⁺ cells.