Ag-specific T cells initiate EC by first infiltrating the conjunctiva, where they become activated by the specific Ag in the conjunctiva.

No abstract

The 4-1BB receptor acts as a costimulator in CD8+ T cell activation. Agonistic stimulation through this molecule by treatment with anti-4-1BB Abs has been demonstrated to inhibit various experimentally induced diseases in animals. However, the effect of anti-4-1BB Abs on experimental allergic diseases has not been reported. We investigated the effect of anti-4-1BB Abs on the development and progression of experimental allergic conjunctivitis in mice. To examine the effects of Abs during the induction or effector phase, actively immunized mice or passively immunized mice by splenocyte transfer were treated with agonistic anti-4-1BB Abs, blocking anti-4-1BB ligand Abs, or normal rat IgG. Eosinophil infiltration into the conjunctiva was significantly reduced in wild-type mice by the anti-4-1BB Ab treatment during either induction or effector phase. Th2 cytokine production by splenocytes and total serum IgE were significantly reduced by the anti-4-1BB Ab treatment, while IFN-γ production was increased. The anti-4-1BB Ab treatment induced a relative increase of CD8-positive cell numbers in the spleens. Moreover, inhibition of eosinophil infiltration by the treatment with anti-4-1BB Abs was also noted in actively immunized IFN-γ knockout mice. Taken altogether, in vivo treatment with agonistic anti-4-1BB Abs in either induction or effector phase inhibits the development of experimental allergic conjunctivitis, and this inhibition is likely to be mediated by suppression of Th2 immune responses rather than up-regulation of IFN-γ.

LPR in the conjunctiva is dominantly mediated by cellular immune responses, whereas EPR in the conjunctiva is putatively mediated by humoral immune responses. Importantly, LPR in the conjunctiva is inducible by Ag-specific IgE alone, although minute.

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.