Memory CD8⁺ T-cell induction specific to RMA by the DNAM-1 ligands. (A) Groups of 10 C57BL /6 mice were primarily inoculated with mock-transduced or Cd155-transduced RMA tumor cells. Mice that had rejected 1 × 10⁵Cd155-transduced RMA tumor cells were divided into 2 groups and pretreated (intraperitoneally) with either anti-CD8 mAb or control immunoglobulin, and rechallenged subcutaneously in the back with 1 × 10⁵ parental RMA tumor cells at 70 days after the primary tumor inoculation. Tumor size in each mouse was measured twice a week and the mean values were plotted. (B) CD8⁺ T cells were separated from spleen in mice 14 to 18 days after inoculation with RMA-mock or RMA-CD155 and stimulated in vitro with gagL peptide in the presence of splenocytes that were used as APCs. The frequency of the peptide-specific CD8⁺ T cells, defined as IFN-γ–producing cells, was determined by ELISPOT assay, as described in “Materials and methods.” Error bars indicate 1 SD.