In line with this, high levels of circulating tumor-antigen-specific TH1 CD4+ T cells and low levels of CD4+ cells co-expressing the immune-checkpoints programmed cell death protein 1 (PD-1) and T cell immunoglobulin and mucin-domain containing-3 (Tim-3) predict better survival in lung cancer patients (99). This evidence concerns the gene PDCD1 and lung cancer.