PDCD1 and cancer: We found that the mean serum PD-L1 levels (Figure 1A) and PD-1 positive rate for peripheral CD4+ T cells (Figure 1B) and CD8+ T cells (Figure 1C) in patients with cancer were significantly higher than those in healthy donors (p<0.01, p<0.05 and p<0.05, respectively), which were consistent with previous reports (20, 33).