ILT2 Identifies an Unexploited Pool of Intratumoral CD8+ Bystander T Cells with TCR-Independent Cytotoxicity in Renal Cell Carcinoma

Immune checkpoint inhibitors (ICI) 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. In this study, we deeply characterized CD8+ILT2+ tumor-infiltrating lymphocytes (TIL) as a distinct subset from CD8+PD-1+ TILs in ccRCC, using high-dimensional spectral flow cytometry, single-cell transcriptomics, and T-cell receptor (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 coculture 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.