PDCD1 and gastric cancer: Moreover, The percentage of PD-1+ cells was robustly increased in both peripheral (4.83 ± 1.18%) and tumor-infiltrating CD8+ T cells (9.34 ± 3.23%) from GC patients when compared with peripheral CD8+ T cells from NC (1.06 ± 0.15%, LSD-t test, all P < 0.0001, Fig. 4c).