CD8A and head and neck squamous cell carcinoma: conducted integrated single-cell transcriptome, spatial transcriptome, and TCR lineage tracing analysis of human head and neck squamous cell carcinoma (HNSCC) patients cohort and found that CD8+ Tpex cells were mainly distributed in cDC1-enriched regions in uninvolved regional lymph nodes (uiLNs).These Tpex cells are the first to be activated following PD-L1 blockade and represent a critical effector population.