PDCD1 and non-small cell lung carcinoma: found proliferation of CD8+ T cells in peripheral blood of patients with NSCLC after PD-1–targeted therapy (10), suggesting that low or median PD-1 level of CD8+ T cells in peripheral blood may indicate activation of CD8+ T cells rather than exhaustion like in tumor microenvironment and is related to the efficacy of PD-1 immunotherapy.