Exertion of the suppressive effects of IFN-γ on experimental immune mediated blepharoconjunctivitis in Brown Norway rats during the induction phase but not the effector phase

Abstract

Background/aims: Interferon gamma (IFN-γ) knockout mice exhibit severe allergic conjunctivitis (AC), indicating that IFN-γ regulates the development of AC. The authors examined whether this inhibitory effect of IFN-γ is exerted during the induction or effector phase of experimental AC.

Methods: Experimental immune mediated blepharoconjunctivitis (EC) was induced in Brown Norway (BN) rats, using ovalbumin (OVA) as the antigen. To investigate the role of IFN-γ in the induction phase, EC was induced by active immunisation and IFN-γ (10 μg/time, total 70 μg), or phosphate buffered saline (PBS) as a control, was injected intraperitoneally every other day from the day of immunisation. The rats were challenged with OVA eye drops 13 days after immunisation, and 24 hours later, the eyes were harvested for histology. To examine the effects of IFN-γ in the effector phase, OVA specific T cells were transferred into syngeneic rats and IFN-γ (10 μg/time, total 50 μg) or PBS was injected each day after the transfer until induction of EC 4 days later with an OVA challenge. To investigate the role of endogenous IFN-γ during the effector phase, an anti-IFN-γ monoclonal antibody (3 mg/time) was injected on days 3 and 4.

Results: Injection of IFN-γ into actively immunised rats suppressed eosinophilic infiltration but not infiltration of mononuclear cells. In contrast, neither IFN-γ nor anti-IFN-γ affected EC in passively immunised rats.

Conclusion: IFN-γ is a suppressive cytokine for the development of EC and exerts this suppressive effect during the induction phase.