Tumor-specific cytolytic CD4 T cells mediate immunity against human cancer

CD4 T cells have been implicated in cancer immunity for their helper functions. Moreover, their direct cytotoxic potential has been shown in some patients with cancer. Here, by mining single-cell RNA-seq datasets, we identified CD4 T cell clusters displaying cytotoxic phenotypes in different human cancers, resembling CD8 T cell profiles. Using the peptide-MHCII-multimer technology, we confirmed ex vivo the presence of cytolytic tumor-specific CD4 T cells. We performed an integrated phenotypic and functional characterization of these cells, down to the single-cell level, through a high-throughput nanobiochip consisting of massive arrays of picowells and machine learning. We demonstrated a direct, contact-, and granzyme-dependent cytotoxic activity against tumors, with delayed kinetics compared to classical cytotoxic lymphocytes. Last, we found that this cytotoxic activity was in part dependent on SLAMF7. Agonistic engagement of SLAMF7 enhanced cytotoxicity of tumor-specific CD4 T cells, suggesting that targeting these cells might prove synergistic with other cancer immunotherapies.

Automated summary

CD4 T cells displaying cytotoxic phenotypes were identified in different human cancers through mining single-cell RNA-seq datasets. Ex vivo confirmation of the cytolytic tumor-specific CD4 T cells was achieved using peptide-MHCII-multimer technology. The cytotoxic activity of these cells, partially dependent on SLAMF7, was demonstrated to have delayed kinetics compared to classical cytotoxic lymphocytes, and agonistic engagement of SLAMF7 enhanced their cytotoxicity, indicating potential synergy with other cancer immunotherapies.