CD4+ T cells activated under the Th1 polarizing condition respond to rhIL-7 after transferring into CTX-conditioned tumor-bearing hosts. The schema outlines the timeline of experimental procedures. Balb/c mice were inoculated with A20HA tumors subcutaneously in one flank. When tumor sizes reach ~170 mm2, mice were treated with CTX (150 mg/kg) followed by adoptive transfer of in vitro-differentiated HA-specific Th1 CD4 T cells (1 × 106 Th1 cells/mouse). A cohort of mice were then subcutaneously injected rhIL-7 (10 ug/injection) at the indicated time points. (A) Phenotypic characterization of in vitro-cultured HA-specific Th1 CD4 T cells. Cytokine profile and Foxp3 level of the cultured Th1 cells were evaluated by FACS. Numbers indicate the percentage of cells positive for the assayed marker. (B) IL-7Rα expression on in vitro-cultured HA-specific Th1 CD4+ T cells before adoptive transfer. (C) rhIL-7 administration enhances the expansion and maintenance of the infused Th1 cells. Tail blood samples collected at the indicated time points were analyzed for donor Th1 cell frequencies by FACS. (D) rhIL-7 administration leads to accelerated complete tumor rejection. The numbers of day needed to achieve complete tumor rejection are plotted. Results are pooled from 2 independent experiments. ***P < 0.001.