PDCD1 and cancer: Analyses of CD8+ PD-1+ CD107a+ TCM cells showed that negative control cells that were not activated by anti-hCD3 or co-cultured with cancer cells had minor levels of CD107a-expressing cells (0.3% ± 0.54%) compared to positive control cells that were activated by anti-hCD3, which had significantly higher levels of cells expressing CD107a (8.7% ± 5.2%).