Synergism between IL-2 and CpG increases the magnitude of TRP-2_180-188–specific CD8⁺ T-cell responses after BMT. (A) Examples are shown of CD8⁺ T-cell responses in tumor-bearing mice that received either the vaccination regimen described in Figure 2A that consisted of TRP-2_180-188 + CpG + IFA vaccines and systemic IL-2 or TRP-2_180-188 + CpG + IFA vaccines with control injections substituted for IL-2 or TRP-2_180-188 in IFA without CpG but with systemic IL-2. Vaccination was initiated 14 days after BMT. Peptide stimulation and ICCS were performed as in Figure 2. The percentage of CD8⁺ T cells that produced IFNγ in response to TRP-2_180-188 is shown on each plot. (B) The regimen consisting of TRP-2_180-188 + CpG + IFA vaccines, and systemic IL-2 elicited larger TRP-2_180-188–specific CD8⁺ T-cell responses as a percentage of total CD8⁺ T cells than regimens with IL-2 omitted, CpG omitted, or both IL-2 and CpG omitted (n = 8-10 mice per group). (C) The regimen consisting of TRP-2_180-188 + CpG + IFA vaccines and systemic IL-2 generated larger absolute numbers of TRP-2_180-188–specific CD8⁺ T cells than regimens with IL-2 omitted, CpG omitted, or both IL-2 and CpG omitted (n = 8-10 mice per group). (D) Mice underwent BMT and 14 days later they were injected with 100 000 B16F1 cells subcutaneously. The mice were then randomly divided into 3 groups. Starting on the same day as tumor injection, each group received 1 of 3 regimens: TRP-2_180-188 + CpG + IFA vaccines and systemic IL-2 (CpG+IL-2), TRP-2_180-188 + CpG + IFA vaccines without IL-2 (CpG), or TRP-2_180-188 in IFA without CpG but with systemic IL-2 (IL-2). The tumor size of the CpG + IL-2 group was significantly smaller than either of the other 2 groups (P < .004) at the indicated (*) time points (n = 12 mice per group).