T regulatory and Th17 cells in chronic rhinosinusitis with polyps

Chronic rhinosinusitis (CRS) is categorized into 2 types based on the absence (CRSsNP) and presence of nasal polyps (CRSwNP). Although CRSsNP patients lack nasal polyps, the mucosa may show variable degrees of polypoid change. This raises the question of whether or not the classification system is an over simplification and that CRSsNP and CRSwNP only represent 2 phenotypic extremes along a broader spectrum of immunologically different disease processes. To investigate this, adaptive and innate immune cells were compared in the different tissue types within CRSsNP and CRSwNP patients.

Tissue from 15 CRSwNP, 6 CRSsNP, and 8 healthy control patients was obtained prospectively. Nonpolypoid mucosa, polypoid tissues, and polyps were obtained at the time of endoscopic sinus surgery and analyzed using flow cytometry for various adaptive and innate immune cell subsets.

In the polyps from CRSwNP patients there were significantly more T regulatory (Treg) cells (12.86 ± 12.60 vs 2.83 ± 4.68) and Th17 cells (16.12 ± 11.75 vs 2.31 ± 2.13) compared to the polypoid tissue from CRSsNP patients. Cellular infiltrates in the nonpolypoid or polypoid mucosa of the different patient categories showed no difference in CRSwNP, CRSsNP and control groups.

This observational study identified an increase in Treg and Th17 cells in CRSwNP patients implying that these cells may be implicated in polyp development. Importantly it also identified a similar inflammatory infiltrate in nonpolyp or polypoid mucosa across control, CRSsNP, and CRSwNP groups inferring that polyps should be sampled when studying CRSwNP.