PD-1 and TIM-3 differentially regulate subsets of mouse IL-17A-producing gamma delta T cells

IL-17A-producing gamma delta T cells in mice consist primarily of V gamma 6(+) tissue-resident cells and V gamma 4(+) circulating cells. How these gamma delta T cell subsets are regulated during homeostasis and cancer remains poorly understood. Using single-cell RNA sequencing and flow cytommetry, we show that lung V gamma 4(+) and V gamma 6(+) cells from tumor-free and tumor-bearing mice express contrasting cell surface molecules as well as distinct co-inhibitory molecules, which function to suppress their expansion. V gamma 6(+) cells express constitutively high levels of PD-1, whereas V gamma 4(+) cells upregulate TIM-3 in response to tumor-derived IL-1 beta and IL-23. Inhibition of either PD-1 or TIM-3 in mammary tumor-bearing mice increased V gamma 6(+) and V gamma 4(+) cell numbers, respectively. We found that genetic deletion of gamma delta T cells elicits responsiveness to anti-PD-1 and anti-TIM-3 immunotherapy in a mammary tumor model that is refractory to T cell checkpoint inhibitors, indicating that IL-17A-producing gamma delta T cells instigate resistance to immunotherapy. Together, these data demonstrate how lung IL-17A-producing gamma delta T cell subsets are differentially controlled by PD-1 and TIM-3 in steady-state and cancer.