PDCD1 and neoplasm: According to the latest research by Lilin Ye et al., there exists a group of TCF-1+ TOX− tumor-specific memory CD8+ T cells (TTSM) in tumor-draining lymph nodes (TdLN), which have a typical memory T cell phenotype and potent anti-tumor capabilities with less exhaustion, representing the real CD8+T cell subpopulation that responds to PD-1/PD-L1 inhibitors [86].