PDCD1 and neoplasm: Notably, we found that CD8+ T cells in tumours with PD-1+CD8+ T cells high infiltration expressed increased immune checkpoints, including cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) and T-cell immunoglobulin domain and mucin domain-3 (TIM-3) while decreased effector cytokines, perforin 1 (PRF1) (Fig. 4b) than their counterparts.