有效的抗肿瘤免疫取决于肿瘤和细胞毒性免疫细胞（尤其是细胞毒性T细胞）之间的特异性结合。尽管研究这些细胞间相互作用对于表征免疫反应和指导免疫治疗应用至关重要，但在活细胞环境中直接定量检测肿瘤-T 细胞相互作用仍然具有挑战性。我们在此报告了一种光催化活细胞相互作用标记策略（CAT-Cell），该策略依赖于醌甲基化物部分的生物正交解衰，以灵敏、选择性地研究和量化肿瘤-T细胞相互作用。通过开发针对捕获细胞间相互作用 (CCIs) 进行优化的醌甲基化物衍生探针，我们证明了 CAT-Cell 检测由各种类型的受体-配体对（例如 CD40-CD40L、TCR-pMHC）引导的 CCI 的能力，以及进一步量化了肿瘤-T 细胞相互作用的强度，这对于评估抗肿瘤免疫反应至关重要。我们进一步应用 CAT-Cell 对小鼠模型的脾细胞和实体瘤样本上的肿瘤特异性 T 细胞相互作用进行离体定量。最后，通过将 CAT-Cell 与抗原特异性靶向系统集成以及用于肿瘤-自然杀伤细胞相互作用检测，证明了 CAT-Cell 的广泛兼容性和实用性。通过利用醌甲基化物的生物正交光催化解腐化学，CAT-Cell 提供了一个灵敏、可调、通用和非侵入性的工具箱，用于揭示和量化活细胞环境下关键但微妙的肿瘤免疫相互作用。

Effective antitumor immunity hinges on the specific engagement between tumor and cytotoxic immune cells, especially cytotoxic T cells. Although investigating these intercellular interactions is crucial for characterizing immune responses and guiding immunotherapeutic applications, direct and quantitative detection of tumor-T cell interactions within a live-cell context remains challenging. We herein report a photocatalytic live-cell interaction labeling strategy (CAT-Cell) relying on the bioorthogonal decaging of quinone methide moieties for sensitive and selective investigation and quantification of tumor-T cell interactions. By developing quinone methide-derived probes optimized for capturing cell-cell interactions (CCIs), we demonstrated the capacity of CAT-Cell for detecting CCIs directed by various types of receptor-ligand pairs (e.g., CD40-CD40L, TCR-pMHC) and further quantified the strengths of tumor-T cell interactions that are crucial for evaluating the antitumor immune responses. We further applied CAT-Cell for ex vivo quantification of tumor-specific T cell interactions on splenocyte and solid tumor samples from mouse models. Finally, the broad compatibility and utility of CAT-Cell were demonstrated by integrating it with the antigen-specific targeting system as well as for tumor-natural killer cell interaction detection. By leveraging the bioorthogonal photocatalytic decaging chemistry on quinone methide, CAT-Cell provides a sensitive, tunable, universal, and noninvasive toolbox for unraveling and quantifying the crucial but delicate tumor-immune interactions under live-cell settings.