Tumor relapse after chemoimmunotherapy is associated with reacquisition of Foxp3 and PD-1 in CD4⁺ effector cells. Following the experimental procedure outlined in Figure 2, we monitored mice for survival. (A) The Kaplan-Meier plot depicts overall survival. Results shown are pooled data from 2 independent experiments. The number of mice in each group is shown. (B) Correlation of tumor relapses with up-regulation of PD-1 and Foxp3 in tumor-specific donor CD4⁺ T cells. At different time points, tail blood samples or spleen cells from the mice treated with combination of Cy and CD4⁺ T-cell transfer were collected and subjected to FACS analysis. Plots of PD-1 vs Foxp3 are gated on divided donor CD4⁺ T cells. Plots shown are representative blood sample staining. Numbers indicate the percentage of cells in each quadrant. (C) The results of all samples are presented as percent of PD-1^hi cells or percent of Foxp3⁺ cells in divided donor cells and summarized in scatter plots. Horizontal bars represent mean values.