Tumor-specific cytolytic CD4 T cells involved in human cancer immunity

Abstract

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