PRECISE-seq reveals disease-relevant TCR repertoires with phenotypic plasticity.

Linking T cell phenotypes with antigen specificity and functional avidity is critical for understanding in vivo immune responses in infection and cancer. Here, we develop PRECISE-seq, a method that integrates multi-omics T cell analysis with contact-dependent proximity labeling for rapid screening of disease-relevant T cell repertoires, and for linking the relative TCR avidity with T cell phenotypes at single-cell resolution. PRECISE-seq accurately retrieves CMV-specific clonotypes from human peripheral blood and quantitatively measures functional avidity in physiological contexts. We find that high-potency CMV-specific T cells preferentially acquire an exhausted phenotype. In tumors, polyclonal tumor-reactive CD8+ T cells predominantly differentiate into a protumor Ly49+ regulatory state (TLy49), characterized by inhibitory killer cell lectin-like receptor expression and originating from effector memory T cells along a trajectory distinct from exhaustion. Notably, PD-1 blockade reduces TLy49 formation and promotes effector revival, which correlates with responsiveness to immunotherapy. Together, PRECISE-seq enables high-resolution mapping of TCR potency and T cell phenotype, revealing a regulatory axis shaping T cell fate in tumors.