Increased expression of transcription factor Bcl-6 in chronic rhinosinusitis with nasal polyps.

B cell activation and excessive immunoglobulin (Ig) production were suggested as the key molecular events of chronic rhinosinusitis with nasal polyp (CRSwNP). However, whether T follicular cells (Tfh cells) were involved in this process has not been documented. In this study, 22 CRSwNP patients and 12 normal controls were enrolled, Bcl-6 (the key transcription factor for Tfh cell differentiation) immunoreactivity was examined by immunohistochemical staining, and the mRNA and protein expression of Bcl-6 and IL-21 was examined using qPCR, ELISA and Western blot, respectively. Moreover, the frequencies of Bcl-6(+)CD4(+) cells (Tfh cells) in polyp tissues and normal controls were measured by flow cytometry. We found that Bcl-6 mRNA and protein levels, as well as the frequencies of Bcl-6(+)CD4(+) cells were significantly increased in polyp tissues compared with normal controls. The frequencies of Bcl-6(+)CD4(+) cells were found to be significantly associated with B cell cluster formation, tissue eosinophilia, asthma comorbidity and polyp recurrence. These findings thus added a new insight into the molecular mechanisms underlying CRSwNP and raise the possibility that Tfh cells could be a novel therapeutic target for difficult-to-treat CRSwNP.