IL-17A-Producing γδT Cells Inhibit the Formation of Malignant Pleural Effusions

γδT cells are an important source of IL-17A and play an anti- or protumor role depending on the surrounding microenvironment. The precise role of γδT cells in the development of malignant pleural effusions (MPE) remains unknown. Using flow cytometry, we analyzed the distribution and differentiation of γδT cells in wild-type (WT) and IL-10 mice. We carefully elucidated the influence of γδT cells on the formation of MPE by depleting γδT cells from WT, IL-10, and IL-17a mice. The distribution of γδT17 cells in human MPE and peripheral blood was also determined. Our data showed that both γδT cells and IL-17A-producing γδT (γδT17) cells accumulated in murine MPE, and IL-10 deficiency enhanced their accumulation. γδT cells were the main source of IL-17A in MPE for both WT and IL-10 mice. IL-10 inhibited the chemotactic response of γδT cells to MPE and the proliferation of these cells. IL-10 suppressed γδT cell secretion of IL-17A via RORγt. The ablation of γδT cells accelerated MPE accumulation in both WT and IL-10 mice, but it did not influence MPE accumulation in IL-17a mice. Patients with higher frequencies of γδT17 cells had significantly longer survival times than patients with lower frequencies of γδT17 cells. Taken together, our data demonstrate that γδT17 cells play an inhibitory role in the progression of MPE, and the accumulation of γδT17 cells in MPE is suppressed by IL-10.