Re-activation and clonal expansion of tumor-specific antigen (TSA)-reactive T cells are critical to the success of checkpoint blockade and adoptive transfer of tumor-infiltrating lymphocyte (TIL)-based therapies. There are no reliable markers to specifically identify the repertoire of TSA-reactive T cells due to their heterogeneous composition. We introduce FucoID as a general platform to detect endogenous antigen-specific T cells for studying their biology. Through this interaction-dependent labeling approach, intratumoral TSA-reactive CD4⁺, CD8⁺ T cells, and TSA-suppressive CD4⁺ T cells can be detected and separated from bystander T cells based on their cell-surface enzymatic fucosyl-biotinylation. Compared to bystander TILs, TSA-reactive TILs possess a distinct T cell receptor (TCR) repertoire and unique gene features. Although exhibiting a dysfunctional phenotype, TSA-reactive CD8⁺ TILs possess substantial capabilities of proliferation and tumor-specific killing. Featuring genetic manipulation-free procedures and a quick turnover cycle, FucoID should have the potential of accelerating the pace of personalized cancer treatment.

肿瘤特异性抗原 (TSA) 反应性 T 细胞的重新激活和克隆扩增对于检查点阻断和基于肿瘤浸润淋巴细胞 (TIL) 疗法的过继转移的成功至关重要。由于 TSA 反应性 T 细胞的异质组成，没有可靠的标记物可以专门识别它们的库。我们介绍 FucoID 作为检测内源性抗原特异性 T 细胞以研究其生物学的通用平台。通过这种相互作用依赖的标记方法，肿瘤内 TSA 反应性 CD4 ⁺、CD8 ⁺ T 细胞和 TSA 抑制性 CD4 ⁺基于细胞表面酶促岩藻糖基生物素化，可以检测 T 细胞并将其与旁观者 T 细胞分离。与旁观者 TIL 相比，TSA 反应性 TIL 具有独特的 T 细胞受体 (TCR) 库和独特的基因特征。尽管表现出功能失调的表型，但 TSA 反应性 CD8 ⁺ TIL 具有强大的增殖和肿瘤特异性杀伤能力。FucoID 具有无基因操作程序和快速周转周期，应该具有加快个性化癌症治疗步伐的潜力。