Impact of IL-17-producing γδ T cells on chronic otitis media induced by nontypeable Haemophilus influenzae in a mouse model

Nontypea b le Haemophilus influenzae (NTHi) is considered a major pathogen underlying middle ear infection. This study aimed to investigate the impact of IL-17 on chronic otitis media (COM) induced by NTHi in mice. NTHi was inoculated into the tympanic bulla with eustachian tubal obstruction. Middle ear effusions (MEEs) and tissues were collected on days 3, 14, and at 1, 2, and 6 months after injection. The expression of interleukin-17A (IL-17A) in MEEs was significantly elevated compared to that in the control group at the translational and transcriptional levels during the experiments. The quantities of IL-17-pr oducing gamma delta T cells wer e significantl y incr eased compar ed to that in the contr ol gr oup during COM, but that of Th17 cells did not. Depletion of gamma delta T cells by anti-gamma delta T-cell r ece ptor (TCR) monoclonal antibody (mAb) administration significantly decreased the bacteria counts and the concentrations of IL-1 ,6, IL-6, IL-17A, TNF-alpha, and IL-10 in MEEs. Our results suggest that IL-17 may play an important role in prolonging the inflammation in the middle ear in COM and that IL-17-producing gamma delta T cells may contribute to the exacerbated inflammatory response in the middle ear. In this study, anti-gamma delta TCR mAb administration was found to improve chronic middle ear inflammatory conditions.