CXCL8 and nasal cavity polyp: For the nine samples obtained from rCRSwNP patients, the IL-8-producing ability of PMNs isolated from nasal polyps was enhanced in response to IL-15 treatment (posttreatment IL-8 level: 3.18-fold elevations compared to the pretreatment IL-8 level) (p < 0.05) (Figure 4B).