Contribution of IL-17-producing γδ T cells to the efficacy of anticancer chemotherapy

By triggering immunogenic cell death, some anticancer compounds, including anthracyclines and oxaliplatin, elicit tumor-specific, interferon-γ- producing CD8⁺ αβ T lymphocytes (Tc1 CTLs) that are pivotal for an optimal therapeutic outcome. Here, we demonstrate that chemotherapy induces a rapid and prominent invasion of interleukin (IL)-17-producing γδ (Vγ4⁺ and Vγ6 ⁺) T lymphocytes (γδ T17 cells) that precedes the accumulation of Tc1 CTLs within the tumor bed. In T cell receptor δ^-/- or Vγ4/6^-/- mice, the therapeutic efficacy of chemotherapy was compromised, no IL-17 was produced by tumor-infiltrating T cells, and Tc1 CTLs failed to invade the tumor after treatment. Although γδ T17 cells could produce both IL-17A and IL-22, the absence of a functional IL-17A-IL-17R pathway significantly reduced tumor-specific T cell responses elicited by tumor cell death, and the efficacy of chemotherapy in four independent transplantable tumor models. Adoptive transfer of γδ T cells restored the efficacy of chemotherapy in IL-17A^-/- hosts. The anticancer effect of infused γδ T cells was lost when they lacked either IL-1R1 or IL-17A. Conventional helper CD4⁺ αβ T cells failed to produce IL-17 after chemotherapy. We conclude that γδ T17 cells play a decisive role in chemotherapy-induced anticancer immune responses.