EXPRESSION OF INTERLEUKIN-18 IN MURINE CONTACT HYPERSENSITIVITY

In this study, we made a mouse model for contact hypersensitivity (CH) using oxazolone as a contact allergen and examined the expression of interleukin-18 (IL-18) in the diseased skin sites at both mRNA and pro tein levels. In the kinetic study by semiquantitative RT-PCR, IL-18 mR NA was constitutively produced in normal murine skin but increased sig nificantly at 12 h and peaked at 24 h in the ear skin of CH mice. A po sitive correlation was confirmed between the IL-18 mRNA signal and CH, as measured by mouse ear swelling response. Histologically, in situ h ybridization showed that the IL-18 mRNA signal was weakly observed in the dermis but not the epidermis of normal skin, whereas the IL-18 mRN A signal was found intensively in the dermis, particularly in inflamma tory cell areas. Using IL-18-specific antibody immunostaining, it was further found that IL-18 protein production had a histologic location similar to that of IL-18 mRNA in both normal and CH mice. The present study suggests that IL-18 may be implicated in the pathogenesis of mur ine CH.