Overall, The percentage of PD-1+CD45+ cells (R2 = 0.01, P = 0.0001, Fig. 4A), PD-1+CD3+ T cells (R2 = 0.015, P < 0.0001, Fig. 4B), PD-1+CD4+ Th cells (R2 = 0.02, P < 0.0001, Fig. 4C) and PD-1+CD3+CD8+ CTL (R2 = 0.006, P = 0.0036, Fig. 4D) showed an increase trend with age in both cancer patients and healthy individuals (Supplementary Fig. 5). Here, PDCD1 is linked to cancer.