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Background Renal cell carcinoma (RCC) responds to immunotherapy despite its low tumor mutational burden (TMB). Interestingly, the degree of CD8 + T cell infiltration in RCC negatively correlates with outcomes, suggesting that a deeper understanding of the tumor microenvironment may provide critical insight to improve outcomes.Methods Multi-omics approaches including flow cytometry, scRNA-seq, scTCR-seq, and CITE-seq were used to compare immune cell composition, gene expression, and cell-cell interactions among a cohort of primary breast cancer, head and neck squamous cell carcinoma, non-small cell lung cancer, and RCC specimens. Putative tumor specificity was determined by flow cytometry following coculture with autologous tumor cells.Results Flow cytometry analysis of tumor-infiltrating lymphocytes (TILs) revealed increased exhausted CD8 + (Tex) and CD4+CD8+ T cells and decreased CD4+ T cells including regulatory T cells in RCC compared to other tumors. scRNA-seq analysis confirmed these results and highlighted Tex cells as a major population of CD8+ T cells. Biomarker analysis of tumor-reactive CD8+ T cells (4-1BB+, CD39+CD103+) as well as a gene signature indicative of neoantigen reactivity, revealed that Tex and CD4+CD8+ T cell populations contain putative tumor-reactive T cells. Tumor reactivity of CD4+CD8+ T cells was demonstrated by increased 4-1BB and OX40 expression following restimulation with autologous tumor cells.Conclusions Exhausted CD8 + and CD4+CD8+ T cells in RCC contain tumor-reactive T cells and may represent a novel cell population capable of targeting RCC, suggesting additional functional characterization of these populations is warranted. Understanding mechanisms of T cell exhaustion and its reversal also has important implications for therapeutic treatment of RCC and other TMB-low, potentially immunotherapy-refractory, tumors.Ethics Approval Signed informed consent was obtained before enrollment. The study was approved by the Providence St. Joseph Health Institutional Review Board – Oregon (IRB #06-108).