TH17 cells in tumour immunity and immunotherapy

T helper 17 (TH17) cells are found in human and mouse tumours. However, the numbers of TH17 cells are limited and are lower than that of other T cell subsets, such as regulatory T (TReg) cells, in the same tumour microenvironment.TH17 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.TH17 cells and IL-17-producing CD8+ T cells induce potent tumour eradication in mice.Tumour-infiltrating TReg cells suppress TH17 cell expansion in tumours, partly through the adenosinergic pathway.The antitumour activity of TH17 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 TH17 cells, TH17 cell-associated cytokines (IL-17 and IL-23) and tumour immunopathology is likely to be highly context dependent.