PDCD1 and head and neck squamous cell carcinoma: As displayed in Figure 6E, PVR/TIGIT, NECTIN2/CD226, and FAM3C/PDCD1 were relatively more strongly expressed in Plac1+ epi‐CD4+ T cells than Plac1− epi‐CD4+ T cells and PVR was specific for Plac1+ tumor cells (Figure S12A,B, Supporting Information), which was subsequently validated in HNSCC cells in vitro and in the TMA cohort by mIF (Figure S13A,B, Supporting Information, Figure 6H).