Fig. 2.

Endogenous IL-15, but not IL-2, enhances the in vivo antitumor activity of adoptively transferred CD8⁺ T cells. WT, IL-15^–/–, and IL-2^–/– mice bearing 14-d s.c. B16 tumors received sublethal irradiation and were left untreated as controls or given a triple regimen of 6 × 10⁶ pmel^IL2 cells, rFPhgp100 vaccine, and exogenous IL-2 (36 μg per dose). Tumors grew similarly in untreated WT (⋄), IL-15^–/– (□), and IL-2^–/– (▵) controls. (A) The treatment effect of the combined immunotherapy regimen is impaired in IL-15^–/– hosts (▪) relative to WT controls (○). (B) Treatment in IL-2^–/– hosts (▴) is similar to that of WT controls (•). Data shown are representative of two independent experiments.