Posttransplant vaccination generates a more effective antitumor immune response than vaccination in the nontransplant setting.
(A) BALB/c mice underwent a syngeneic BMT from non–tumor-bearing donors consisting of 4 × 106 T-cell–depleted BM cells plus 4 × 107 splenocytes as described in “Materials and methods.” Nontransplanted mice were included for comparison. At the indicated times post-BMT, mice were challenged with A20 tumor (1 × 105 intravenously) and vaccinated 5 days later by a subcutaneous injection of irradiated A20/GM-CSF (1 × 106). Mice were followed twice a week for the presence of tumor, which was confirmed at autopsy. (B) Mice underwent syngeneic BMT with grafts consisting of 4 × 106 T-cell–depleted marrow alone or 4 × 106 T-cell–depleted marrow plus 4 × 107 splenocytes as indicated. Three weeks after transplantation, they were challenged with a 10-fold greater dose of A20 tumor (1 × 106), followed 5 days later by subcutaneous vaccination with irradiated A20/GM-CSF (1 × 106). Nontransplanted mice received the same tumor challenge and vaccination.
