Local IL-17 positive T cells are functionally associated with neutrophil infiltration and their development is regulated by mucosal microenvironment in nasal polyps.

OBJECTIVE AND DESIGN: IL-17 plays essential roles in neutrophilic inflammation in the lower respiratory tract, however, the characteristics of local IL-17+ T cells in nasal inflammatory mucosa are not fully understood. We investigated the roles of IL-17+ T cells in regulating neutrophil infiltration and the effect of the mucosal microenvironment in modulating IL-17+ T cell differentiation in CRSwNP tissues. SUBJECTS: 47 polyp tissues from chronic rhinosinusitis with nasal polyps (CRSwNP) patients without corticosteroid therapy and 26 tissues from healthy mucosa were obtained. METHODS: Immunohistochemistry and flow cytometry were used to analyze the neutrophil infiltration, local IL-17+ T cell subsets, as well as cytokine producing profiles of IL-17+ T cell; tissue homogenates were used to study neutrophil migration and IL-17+ T cell differentiation. RESULTS: Increase of IL-17+ cells and IL-17+ T cell subsets was significant in polyp tissues versus controls, IL-17+ cell number was positively correlated with neutrophil infiltration; while homogenates from polyp tissues with high IL-17 promoted neutrophil migration in vitro. IL-17 response was found in polyp-derived T cells upon Staphylococcus aureus infection. IL-17+ T cells were also down-regulated in polyps from patients treated with glucocorticoid steroids, and exhibited poly-functionality patterns in polyp tissues. Finally, IL-17+ T cell differentiation could be induced by IL-23, and homogenates from polyps could enhance IL-17+ T cell development. CONCLUSIONS: This study determined a functional association of IL-17+ T cells with neutrophils in CRSwNP, and revealed that polyp microenvironment could promote IL-17+ T cell differentiation, suggesting a potential feedback role for IL-17+ T cell development and local neutrophilic inflammation.