Establishment of T-helper type 2 clone-induced eosinophilia in mouse conjunctiva

Transfer of a T-helper type 2 clone into conjunctiva induces corneal damage in mice

PURPOSE

We established a T-helper Type 2 (Th2) clone-induced conjunctival eosinophilia model by injecting D10.G.4.1 (D10) cells, a murine Th2 clone, and conalbumin, its specific antigen, into conjunctiva of AKR/J mice. Using this model, we investigated the effect of a coinjection of D10 cells and conalbumin into conjunctiva on corneal damage.

METHODS

Corneal fluorescein staining scores and eosinophil peroxidase (EPO) activity in conjunctiva were measured after coinjection of D10 and conalbumin into conjunctiva, and the effects of cyclosporine A, betamethasone, and anti-interleukin-5 antibody on staining scores and EPO activity were examined.

RESULTS

Coinjection of D10 and conalbumin induced an increase of the corneal fluorescein staining score after 24, 48, and 96 hours and 10 days. EPO activity in conjunctiva increased time-dependently until 24 hours after coinjection. The increase in the staining score followed the time dependent increase in EPO activity. The instillation of cyclosporine A, an inhibitor of cytokine production from T-cells, and betamethasone significantly inhibited the increase in corneal fluorescein score and EPO activity. Intraperitoneal administration of anti-interleukin-5 monoclonal antibody, which inhibits the infiltration of eosinophils into the conjunctiva, completely inhibited the increase in staining score.

CONCLUSION

The transfer of the Th2 clone into the murine conjunctiva induced corneal damage, which may have been caused by Th2 cell-produced interleukin-5 that mediated the activation of eosinophils.

Interleukin-4–Mediated Infiltration of Eosinophils into the Conjunctiva and Its Suppression by Interferon-γ

PURPOSE

Interleukin (IL)-4 is a T helper (Th)2 cytokine that plays an important role in the development of allergic reactions. It has been suggested that IL-4 is responsible for the infiltration of eosinophils into the conjunctiva during the development of allergic conjunctivitis. However, it is still unclear whether IL-4 is able to induce this eosinophilic infiltration on its own. We investigated whether subconjunctival injection of IL-4 can induce eosinophils to infiltrate into the conjunctiva.

METHODS

Brown Norway rats were subconjunctivally injected with IL-4, eotaxin, or phosphate buffered saline (PBS), and the conjunctivas were harvested for histologic analysis (including immunohistochemistry) 6, 12, 18, and 24 hr later. The harvested conjunctivas were also subjected to reverse transcription-polymerase chain reaction (RT-PCR) analysis to examine chemokine expression. In a separate experiment, the effect of coadministering interferon-gamma (IFN-gamma) along with IL-4 was examined.

RESULTS

The subconjunctival injection of IL-4 induced eosinophil infiltration into the conjunctiva in a dose-dependent manner. IL-4 was as potent as eotaxin. The eosinophilic infiltration started 6 hr after the injection and persisted for up to 24 hr after the injection. Other infiltrating cell phenotypes were noted but were also observed in conjunctivas injected with PBS alone. RT-PCR analysis demonstrated that IL-4 injection did not upregulate chemokine RNA expression in the conjunctiva. Coinjection of IFN-gamma suppressed the infiltration of eosinophils into the conjunctiva induced by IL-4 injection.

CONCLUSIONS

The subconjunctival injection of IL-4 specifically induces eosinophils to infiltrate into the conjunctiva. In addition, IFN-gamma in the conjunctiva can counteract this effect of IL-4.