Restimulation of activated T cells induces additional proliferation with retention of specific anti-tumor efficacy. (A) CD62Llow TDLN cells were activated with anti-CD3 mAb from day 0–2 and again for 14 hrs on day 15. T cells were cultured in the presence of IL-2 (4 U/ml) (closed circle) or IL-2 plus IL-7 (10 ng/ml) (open circle) and the total proliferation is indicated. (B) FACS analysis of activated T cells on day 23 of culture stained for CD4 and CD8. (C) Mice bearing 10-day pulmonary metastases of either MCA205 or MCA207 tumors were pre-treated with 5 Gy TBI then received adoptive transfer of 2.5 × 107 cells cultured with IL-2 alone, the combination of IL-2 plus IL-7, or control HBSS as indicated. Difference between the groups bearing MCA 205 treated with T cells cultured with IL-2 or IL-2 plus IL-7 and all other groups is (P < 0.01). (D) Mice bearing 3-day s.c tumors were pre-treated with 5Gy TBI followed by injection of; HBSS (closed circles), 5 × 106 T cells activated for 5 days (open circles, P < 0.01), 5 × 106 restimulated T cells at day 23 of culture (closed triangles, P = 0.4), 1.5 × 107 re-stimulated T cells (open triangle, P < 0.01), or 4 × 107 re-stimulated T cells (closed square, P < 0.01). Number of mice showing complete regression in each treatment group of 5 mice is indicated in parentheses.