ILT2 identifies an unexploited pool of intratumoral CD8+ bystander T cells with TCR-independent cytotoxicity in renal cell carcinoma

Immune checkpoint inhibitors (ICIs) have improved clear-cell renal cell carcinoma (ccRCC) therapy, yet many patients remain unresponsive. Alternative strategies are needed, and the HLA-G/ILT2 axis has emerged as a promising immunosuppressive pathway. Here, we deeply characterized CD8⁺ILT2⁺ tumor-infiltrating lymphocytes (TILs) as a distinct subset from CD8⁺PD1⁺ TILs in ccRCC, using high-dimensional spectral flow cytometry, single-cell transcriptomics, and TCR clonotype analysis. CD8⁺ILT2⁺ TILs were terminally differentiated, highly cytotoxic “bystander” cells, enriched for virus-specific TCRs. They phenotypically, transcriptionally and functionally mirrored their circulating counterparts, suggesting peripheral recruitment. In dynamic co-culture assays, they exhibited potent TCR-independent cytotoxicity, mediated by activating innate receptors, namely NKG2D. However, HLA-G inhibited this activity, underscoring the immune-evasive role of the HLA-G/ILT2 axis. Our study defines CD8⁺ILT2⁺ TILs as an untapped effector population with potential antitumor activity and a promising therapeutic target in ccRCC. These findings offer new insights into TIL functional diversity and pave the way for innovative immunotherapies beyond conventional ICIs.