Administration of CpG in vivo enhances tumor-specific CD8⁺ T-cell response to posttransplantation DC vaccination. (A,B) Syngeneic transplantations were set up as described in Figure 1A. Fourteen days after transplantation, mice were vaccinated with either TNF-α–matured DC-HA or DC-Con with (CpG in vivo) or without (no CpG) coadministration of CpG in vivo. Some mice received DCs matured with CpG ex vivo followed by HA pulsing (CpG ex vivo). Seven days after vaccination, splenocytes were stained with anti-CD8, anti-Thy1.1, and anti–IFN-γ antibodies and subject to FACS analysis. The percentage of IFN-γ–secreting HA-specific T cells (Thy1.1⁺IFN-γ⁺) among total CD8⁺ T cells is indicated (A). The mean percentage (± SD; n = 4) of IFN-γ–secreting HA-specific T cells among total CD8⁺ T cells is indicated (B). (C) Tumor-free survival. Syngeneic transplantations were set up in the absence of transgenic T cells. Fourteen days after transplantation, mice were vaccinated with DC-HA or DC-Con with or without coadministration of CpG in vivo and monitored for tumor-free survival. Data (n = 10) represent percentages of tumor-free survival over time from the transplant (day 0). Representative results of 2 independent experiments are shown.