Recognition of TAg⁺lymphoma cells by CD8⁺T cells. (A) B cells of 5- to 7-week-old tamoxifen-treated (day 0-4) or untreated mice were isolated on days 17 to 24, activated with cytosine guanine dinucleotide and cocultured with TCR-IV–transduced CD8⁺ T cells for 3 days. The IFN-γ concentration in the supernatant was determined by ELISA. Each dot represents the IFN-γ response to 1 mouse. Shown are combined data of 2 independent experiments. One-way analysis of variance and Sidak’s post hoc test were performed. Adjusted P values are indicated. (B) Nine- to 12-week-old CD19-CreER^T2 × LoxP-Tag mice were tamoxifen treated (day 0-4) or left untouched. The positive control was immunized with 1 × 10⁷ TAg⁺ tumor cells at day −7 (symbols in red). Untreated wt mice served as negative control. On day 14/15, splenocytes were stained with pIV-tetramer and were restimulated with medium (-), TAg peptide IV, or TAg⁺ lymphoma cells. Shown are exemplary FACS plots of tamoxifen-treated CD19-CreER^T2 × LoxP-Tag mice, which stained pIV-tetramer⁻ (upper row) and pIV-tetramer⁺ (lower row). Combined data of 3 independent experiments were analyzed with 1-tailed Mann-Whitney U test. (C) Six- to 9-week-old mice were tamoxifen treated or remained untouched. Mice were immunized IP with 1 × 10⁷ TAg⁺ tumor cells on day 10 or 41 (symbols in red) or stayed nonimmunized. The TAg peptide IV–specific CTL response was evaluated by in vivo cytotoxicity assays on day 17 (left) or day 48/49 (right). Shown are combined data of 2 independent experiments. Two-tailed Mann-Whitney U test (left) and Kruskal-Wallis test with Dunn’s post hoc test (right) were performed. Adjusted P values are indicated.