Integrating Three Functional Subsets of T Cell Immunity Into an Integrative Model for Cancer Immunotherapy

Current cancer immunotherapy relies heavily on tumor-Ag specific T cells (TASTs). While checkpoint blockade has redefined the therapeutic landscape of oncology, this single-mechanism strategy shows limitations from stochastic de novo priming and terminal exhaustion. High-dimensional single-cell data reveal the tumor microenvironment as a heterogeneous immune ecosystem where virus-specific T cells (VSTs) and bystander T cells often predominate over TASTs. We propose an integrative model built on three functional subsets: 1) classical TASTs; 2) VSTs acting as TASTs via viral etiology or molecular mimicry; and 3) bystander T cells representing a tumor-independent compartment. Characterizing these subsets by ontogeny and transcriptional programs suggests their potential utility as predictive biomarkers for checkpoint inhibitor responses and as distinct platforms for adoptive cell transfer strategies. This explains resistance mechanisms in immunologically cold tumors and guides mechanistically distinct therapeutic approaches-from classical priming to in situ viral activation and off-the-shelf cellular products.