Cell origins and significance of IL-17 in malignant pleural effusion.

PURPOSE

T cells are dominant in the immune regulation of malignant pleural effusion (MPE). However, it is unclear about the role of IL-17+ T cells, particularly for IL-17+CD8+ Tc17 cells in antitumor immunity. This retrospective study is aimed at evaluating the prognostic significance of IL-17+ T cells in patients with MPE.

METHODS

The frequency of IL-17+CD4+ Th17 and IL-17+CD8+ Tc17 cells in peripheral blood (PB), pleural fluids (PF), and tumor tissues in 24 patients undergoing thoracoscopy was determined by flow cytometry, immunohistochemistry, and ELISA. The association among the different measures was analyzed by Spearman's correlation tests.

RESULTS

The percentages of PF Th17 and Tc17 cells were significantly higher than those in the PB of MPE patients and healthy controls (p < 0.01). Analysis of Th17 and Tc17 cells in the tumor tissues indicated that the percentages of Th17 and Tc17 cells in the invading tumor edge were significantly higher than those in the non-tumor tissues and intra-tumor regions (p < 0.05). More importantly, the percentages of IL-17+ T cells were associated with prolonged survival of patients with MPE.

CONCLUSIONS

Both Th17 and Tc17 cells were involved in the tumor immunity against MPE. Increased frequency of Tc17 cells may serve as a biomarker for the prognosis of patients with MPE.