Type 2 inflammation and eosinophilic infiltration are prominent pathologic features of chronic rhinosinusitis with nasal polyps (CRSwNP). The purpose of the present study was to determine the roles of Tregs in controlling type 2 inflammation and inhibiting eosinophilic infiltration in CRSwNP. A total of 134 nasal polyps, 67 ostiomeatal complex from chronic rhinosinusitis (CRS) and 62 normal nasal tissues from controls were collected to study the enumeration and function of Tregs cells and the expressions of cytokine profiles via immunofluorescence staining, flow cytometry, qRT-PCR, ELISA, and/or H&E staining. The effects of Tregs on type2 and type3 inflammations were determined in an eosinophilic chronic sinusitis (ECRS) mice model. It was confirmed that the CRSwNP displayed the features of Th2 and Th17 cells-mediated inflammation, accompanying by an increased level of eosinophilic infiltration and the eosinophil cationic protein (ECP), with a decreased frequency of Treg cells. Furthermore, the percentages of CD4+CD25+CD127lowTreg and CD4+CD25+Foxp3+Treg were only decreased in the polyps of CRSwNP but not in the paired peripheral blood. The CRSwNP possessed the decreased Nrp1+Tregs, Helios+Treg, and low TGF-β and interleukin (IL)-10 expressions in Tregs. The ECRS mice showed similar inflammatory characteristics to CRSwNP patients. The adoptive transfer of CD4+CD25+Foxp3+ Treg cells significantly decreased the inflammatory cytokines, eosinophilic chemotactic factors in the mucosa of the ECRS mice without alteration of the immune balance in the peripheral blood and spleen. In conclusion, CRSwNP showed high type 2 and type3 inflammation and defective Tregs. The induced regulatory T cell (iTreg) may correct the imbalance between immune tolerance and effect via limiting the eosinophil recruitment of mucosa in CRSwNP.

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