PDCD1 and neoplasm: Correlation analyses also demonstrated that CD8+ T-cells, CD8+ Tcm, CD8+ naive T-cells, CD4+ memory T cells, and CD4+ naïve T cells were all positively correlated with expressions of these inhibitory receptors in tumor tissues, especially with PD1 and CTLA4 (P < 0.05) (Fig. 2C and 2D).