Phenotypic and functional characteristics of IL-21-expressing CD8+ T cells in human nasal polyps

Although CD4(+) T cells are recognized to play an important role in the inflammatory response of nasal polyps (NPs), the biological functions of CD8(+) T cells in polypogenesis remain unclear. In this study, we analyzed cell markers, cytokine expression and transcription factors in IL-21-expressing CD8(+) T cells in polyp tissues of NP patients. The results showed that the majority of IL-21-producing CD8(+) T cells were effector memory cells and they co-expressed IFN-γ. IL-21-expressing CD8(+) T cells in polyp tissues expressed higher CXCR5, PD-1, and ICOS levels than cells in control tissues and showed significantly higher T-bet and Bcl-6 expression levels compared with IL-21(-)CD8(+) T cells. Purified polyp CD8(+) T cells promoted IgG production from isolated polyp B cells in vitro, and recombinant IL-12 modulated the expression of IL-21, IFN-γ and CD40L in purified polyp CD8(+) T cells. Moreover, the percentage of IL-21(+)CD8(+) T cells in polyp tissues was positively correlated with endoscopic and CT scan scores in NP patients. These findings indicated that polyp CD8(+) T cells, by co-expressing IL-21 and IFN-γ and other markers, display a Tfh cell functionality, which is associated with the clinical severity of NP patients.