DC-induced CD44^hiCD8⁺ T cells retain the ability to kill tumor cells. (A) Naive C3H.SW CD44^loCD8⁺ T cells were separated and stimulated with B6 DCs plus IL-2 plus IL-15. After 5 days of culture, cells were collected, sorted into CD44^hiCD8⁺ and CD44^loCD8⁺ T cells (CD45.2) and transplanted together with C3H.SW T^–BM into lethally irradiated B6 mice (CD45.1) at day 0. At day 7 following BMT, 5000 EL-4 leukemic cells were injected into the peritoneal cavity of these B6 mice. Survival after EL-4 inoculation: ▪, T^–BM (n = 12); •, T^–BM plus unstimulated naive CD8⁺ (n = 9); ×, T^–BM plus B6 DC-induced CD44^loCD8⁺ (n = 8); ▴, T^–BM plus B6 DC-induced CD44^hiCD8⁺ (n = 18). B6 mice receiving C3H.SW T^–BM plus B6 DC-induced CD44^hiCD8⁺ but no EL-4 injection (○, n = 4) were used as controls. (B) The ability of B6 DC-induced CD44^hiCD8⁺ (▪) and CD44^loCD8⁺ T cells (▴) to kill EL-4 cells ex vivo was examined by ⁵¹Cr-release method either prior to or 7 days after their infusion into irradiated B6 mice. Unstimulated C3H.SW CD8⁺ naive T cells (♦) were used as controls, before (♦ and ×) or 7 days (♦) after infusion into B6 mice. (C) The ability of B6 DC-induced CD44^hiCD8⁺ (♦) and CD44^loCD8⁺ T cells (▪) to kill EL-4, C1498, MC57 and NS-1 cells that had been grown in serum-free medium was examined as mentioned in panel B. (D) Neutralizing anti–MHC-I (50 μg/mL), anti-FasL Ab (50 μg/mL), anti–MHC-II, or anti–TNF-α was added into the cytolytic assays containing 8 × 10⁴ CD44^hiCD8⁺ T effector cells and 1 × 10⁴ target cells as indicated. *P < .05 and **P < .01 (anti–MHC-I Ab or anti-FasL Ab versus control IgG), respectively. Results are representative of 2 separate experiments. All values shown in B-D represent means ± SD of triplicate wells.