PDCD1 and cancer: Furthermore, the results of flow cytometry demonstrated that the mean apoptosis rate of peripheral PD-1+ cells (Figure 1D), PD-1+CD4+ T cells (Figure 1E), and PD-1+CD8+ T cells (Figure 1F), as evidenced by Annexin V binding, in patients with cancer was significantly higher than in healthy donors (p<0.001, p<0.001, and p<0.01, respectively).