Conjunctiva Resident γδ T Cells Expressed High Level of IL-17A and Promoted the Severity of Dry Eye.

Purpose: Conjunctival inflammation promotes ocular surface disorders in dry eye disease (DED). Here we identified γδ T cells as the predominant source of IL-17A in the murine conjunctiva and assessed their contribution to the pathogenesis of DED.
Methods: We enrolled 22 patients with DED, and analyzed the proportion of γδ T cells in the conjunctival epithelial samples by flow cytometry. Adult C57Bl/6 wild-type and TCRδ-/- mice were used to induce DED models to investigate the role of γδ T cells. The characteristics of immune cell infiltration and the expression of immune-related cytokines or markers in mouse conjunctiva were analyzed by flow cytometry, Western blot, and quantitative polymerase chain reaction.
Results: The proportion of γδ T cells in the human DED conjunctiva is significantly higher in patients with severe corneal epithelial defects than in mild ones, which is consistently observed in the murine DED model. Further, a high level of IL-17A but not IFN-γ is detected in the conjunctiva of mice. The increased murine IL-17A-producing cells on the conjunctiva are identified as γδ T cells predominantly and Th17 cells to a lesser extent. Ablation of γδ T cells by antibody depletion or genetic deletion of TCRδ alleviates ocular surface damage in the murine DED model.
Conclusions: Our studies evaluate human and experimental murine DED for evidence of γδ T-cell-mediated inflammation and highlight a potential therapeutic synergy by targeting IL-17 and γδ T cells in DED treatment.