Tumor-infiltrating gamma delta T-cells reveal exhausted subsets with remarkable heterogeneity in colorectal cancer.

The γδT-cells recognize infected or transformed cells. However, unlike αβT-cells, γδT-cells are innate-like immune cells, with no major histocompatibility complex restriction requirements. γδT-cells are the main population of intestinal intraepithelial lymphocytes (IELs) and are associated with the antitumor immune response, particularly in colorectal cancer (CRC). Although CD8+ T-cells exhibit dysfunction and even exhaustion in the tumor microenvironment (TME), which contributes to tumor immune escape, whether the same applies to tumor-infiltrating (TI)-γδT-cells is not completely understood. Here, we sought to investigate the expression pattern of inhibitory receptors and functional state of TI-γδT-cells, and reveal the features of exhausted TI-γδT-cells in the CRC TME. We demonstrated that TI-γδT-cells exhibited exhaustion phenotypes and displayed more severe functional exhaustion than TI-CD8+ T-cells or NK-cells in the TME of CRC. In addition, scRNA-seq analysis of TI-γδT-cells revealed three exhausted subsets with remarkable heterogeneity. The presence of three heterogeneous exhausted γδT-cell (Tex) populations, including Texprog , Textran and Texterm were further confirmed by flow cytometry, on the basis of PD-1 and TIM-3 expression. Finally, we revealed that c-Maf not only contributed to γδT-cell exhaustion via upregulation of inhibitory receptors, but also involved in the exhaustion of CD8+ T and NK-cells. c-Maf may also be an important contributor to γδT-cell exhaustion in CRC patients. These findings indicated that TI-γδT-cells exhibit phenotypic and functional exhaustion in the CRC TME. The revealed features of exhausted TI-γδT-cells may provide help for understanding the mechanisms and the association of γδT-cell exhaustion with tumor development and pathogenesis.