Flow cytometry analysis validated the enhanced frequencies of CD3+CD4+CD25hiCD127lo Treg cells in all 4 patients with cancer at 6 weeks following 2 cycles of anti–CTLA-4 and anti–PD-1 mAbs compared with counterparts before treatment and at 7 months when only on anti–PD-1, whereas CD4+ and CD8+ T cell ratios and major CD4+ memory and effector T cell subsets were not affected by mAb treatments (Figure 5, D and E, and Supplemental Figure 7). Here, CTLA4 is linked to cancer.