58 Long-term IFN-γ Treatment Alters Allergic Inflammation-Associated Gene Expression in Conjunctival Fibroblasts

BACKGROUND: Interferon-γ (IFN-γ) is a T helper type 1 (Th1) cytokine which has antiviral, anti-proliferative, and immunomodulatory properties. Despite the presence of IFN-γ in the conjunctiva or tear fluid of patients with severe allergic conjunctivitis, the role of IFN-γ in allergic conjunctivitis is controversial and enigmatic. In this study, we assess the effect of long-term treatment of IFN-γ on human conjuctival fibroblasts. METHODS: Primary cultured fibroblasts derived from human conjunctiva specimens were established. Cultured fibroblasts were incubated with or without IFN-γ (10 ng/mL) for up to 14 days. After IFN-γ treatment, cells were washed out and were re-stimulated with combinations of IL-4 (10 ng/mL) and TNFα (10 ng/mL) for 6 hours. Then, total mRNAs were isolated and mRNA expression levels were measured using a microarray and real time-PCR. RESULTS: In IFN-γ treated fibroblasts in short-term (6 hours), we confirmed the increased expression levels of well-known interferon induced genes, such as MHC class II, IRF1 and CXCL10. Increased expression of CCL11 stimulated by IL-4 + TNFα was suppressed by short-term IFN-γ treatment as described previously. In long-term (14 days) IFN-γ treated cells, the expression of CCL11 and several proinflammatory chemokines, which were associated with Th2 cell and eosinophil migration, was slightly but significantly increased without any other stimulations. Interestingly, IL-4 + TNFα stimulation greatly enhanced the expression levels of these chemokines, suggesting that long-term IFN-γ treatment alters the competency of gene expression potential on these gene loci in contrast to the situation for short term treatment. Time-course analysis of IFN-γ treatment revealed that the treatment of IFN-γ up to 24 hours suppressed the IL-4 + TNFα-induced CCL11 expression, whereas the CCL11 expression was enhanced 3 days after the treatment. CONCLUSIONS: These results uncovered previously unsuspected contribution of IFN-γ to the fibroblasts in allergic inflammatory milieu in terms of the change in production of certain chemokines. In other words, the antagonistic function of IFN-γ to Th2 cells at the early phase may represent only a small part. The intracellular signaling and IFN-γ-dependent secondary events are needed to be explored to explain the long-term effect or the late phase phenomenon after IFN-γ administration.