TH17 cells in tumour immunity and immunotherapy

Abstract

T helper 17 (T_H17) cells are found in human and mouse tumours. However, the numbers of T_H17 cells are limited and are lower than that of other T cell subsets, such as regulatory T (T_Reg) cells, in the same tumour microenvironment. T_H17 cells exhibit polyfunctional features and express several effector cytokines, including interleukin-2 (IL-2), IL-17, granulocyte–macrophage colony-stimulating factor (GM-CSF), interferon-γ (IFNγ) and tumour necrosis factor (TNF) in the human tumour microenvironment. T_H17 cells and IL-17-producing CD8⁺ T cells induce potent tumour eradication in mice. Tumour-infiltrating T_Reg cells suppress T_H17 cell expansion in tumours, partly through the adenosinergic pathway. The antitumour activity of T_H17 cells may be due to their ability to recruit effector T cells, natural killer cells and dendritic cells into the tumour environment and to tumour-draining lymph nodes. The mechanistic and functional relationship between T_H17 cells, T_H17 cell-associated cytokines (IL-17 and IL-23) and tumour immunopathology is likely to be highly context dependent.