Type 1–type 2 interferon imbalance in dry eye disease

PURPOSE: Dry eye disease (DED) is characterized by altered ocular surface proinflammatory and antiinflammatory factors. Interferons (IFNs) are a class of pleiotropic cytokines well known for their antimicrobial, inflammatory, and immunomodulatory roles. Hence, this study investigates the ocular surface expression of different types of IFNs in patients with DED. METHODS: The cross-sectional, observational study included patients with DED and normal subjects. Conjunctival impression cytology (CIC) samples were obtained from the study subjects (controls, n = 7; DED, n = 8). The mRNA expression levels of type 1 IFN (IFNα, IFNβ), type 2 IFN (IFNγ), and type 3 IFN (IFNλ1, IFNλ2, IFNλ3) were measured by quantitative PCR (polymerase chain reaction) in CIC samples. IFNα and IFNγ expression under hyperosmotic stress was also studied in human corneal epithelial cells (HCECs) in vitro. RESULTS: The mRNA expression levels of IFNα and IFNβ were significantly lower and that of IFNγ was significantly higher in DED patients compared to healthy controls. The mRNA levels of IFNα, IFNβ, and IFNλ were significantly lower compared to IFNγ in DED patients. An inverse association between tonicity-responsive enhancer-binding protein (TonEBP; hyperosmotic stress maker) and IFNα or IFNβ expression and a positive association between TonEBP and IFNγ expression was observed in CIC samples. The expression of IFNα was lower than IFNγ in HCECs undergoing hyperosmotic stress compared to HCECs without the stress. CONCLUSION: The presence of an imbalance between type 1 and type 2 IFNs in DED patients suggests newer pathogenic processes in DED, plausible ocular surface infection susceptibility in DED patients, and potential therapeutic targets in the management of DED.