T helper 17 T cells do good for cancer immunotherapy

Evaluation of: Martin-Orozco N, Muranski P, Chung Y et al.: T helper 17 cells promote cytotoxic T cell activation in tumor immunity. Immunity 31(5), 787-798 (2009). The immune system plays an important role in tumor control. Tumor antigen-specific CD4(+) and CD8(+) T cells are being actively exploited in cancer immunotherapy protocols that often attain clinical responses. The T helper (Th)1 effector cytokine profile, epitomized by the production of IFN-gamma, is considered the optimal pathway in controlling tumor growth. In this study, Martin-Orozco challenges this notion by demonstrating that newly defined Th17 effector T cells display a stronger anti-tumor effect vis a vis with Th1 cells. Th17 cells produce the strongly inflammatory cytokines IL-17A and IL-17F, and so far have been implicated in the response to infectious pathogens and in autoimmunity. This study reveals that Th17 cells protect against cancer, not only by triggering a potent nonantigen-specific intratumor inflammatory infiltrate, but also, and remarkably, by providing a more significant help than Th1 cells for the efficient induction, expansion, differentiation and tumor homing of tumor-specific CD8(+) T cells. This study, therefore, sheds new light on the effector functions of Th17 cells and has strong implications for their translation into clinical applications for cancer immunotherapy.