CD4⁺ effector T cells enable and collaborate with intratumoral CD8⁺ T cells to mediate enhanced antitumor effects after chemotherapy. Following the procedures depicted in Figure 2, tumors were excised 7 days after CD4⁺ T-cell transfer and subject to (A) immunofluorescence staining of host CD8⁺ T cells. The representative composite images show CD8⁺ cells (green) and DAPI (blue) staining in tumor sections (original magnification, ×20). (B) Frequency of tumor-infiltrating CD8⁺ T cells measured by flow cytometry analysis. Single-cell suspensions made from resected tumor masses were stained for CD8. Bar graph shows percentage of intratumoral CD8⁺ T cells in each group. Results shown are from 2 independent experiments with 6 mice per group (mean ± SD). (C) Functional analysis of intratumoral CD8⁺ T cells. Granzyme B level was evaluated ex vivo, IFNγ production was assayed by ICS after 4 hours stimulation of purified CD8⁺ T cells with PMA/ionomycin. Representative dot plots are shown, and the results are summarized in scatter plots (**P < .005). (D) Tumor growth kinetics in mice receiving the indicated treatments. Number of mice in each group is given.