In vivo treatment of tumor-bearing mice with STI-571 preserves the responsiveness of tumor-specific CD4+ T cells to vaccination. BALB/c mice were injected intravenously with 1 × 106 A20HA tumor cells on day –10. From day–9 to day 0, half of the mice received intraperitoneal injection of STI-571 (12.5 mg/kg per day) or vehicle alone. On day zero, all the mice received 2.5 × 106 anti-HA TCR+transgenic CD4+ T cells intravenously. On day +9, mice were immunized subcutaneously with 1 × 107 pfu vacc-HA. Animals were killed 6 days later (day +15), and T cells were purified from their spleens as indicated in “Materials and methods.” Purified T cells were mixed with fresh splenocytes and HA-peptide as described in Figure 2. Then 48 hours later, supernatants were collected and assayed for IL-2 (A) or IFN-gamma (B) by ELISA. Values are the mean ± SE of triplicate cultures from 3 mice in each group. Data are expressed as the amount of cytokine produced per 100 clonotype-positive T cells/well and are representative of 3 independent experiments with similar results.
