Th1- and Th2-type cytokines in chronic ocular allergy
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Previous reports have suggested that Th2-type cytokines are important in the pathogenesis of ocular allergic diseases. The purpose of this study is to measure levels and mRNA expression of Th1- and Th2-type cytokines in patients with active vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC).
Tear samples and tear-isolated cells were obtained from 9 healthy participants (CT—controls), 28 VKC, and 6 AKC patients. IL-4, IL-13, and interferon gamma (IFNγ) tear levels were determined by ELISA, and IL-4 and IFNγ tear cell mRNA expression by RT-PCR. Effects of these cytokines on IL-6 and IL-8 secretion, and on ICAM-1 expression by conjunctival fibroblasts, were evaluated by ELISA and flow cytometry respectively.
Interleukin-4 tear levels were increased in VKC and AKC compared with CT, but only IFNγ significantly correlated with corneal involvement. An IL-4/13-dominant profile was found in 50% of VKC and in 17% of AKC patients, while a IFNγ -dominant profile was found in 18% of VKC and in 17% of AKC patients. IL-4 and IFNγ transcripts were detected in tear cells from 11 out of 12 VKC patients. IFNγ upregulated expression of ICAM-1 on conjunctival fibroblasts and the secretion of IL-6 and IL-8.
Although both IL-4 and IFNγ are detected in tears, only IFNγ levels correlated with disease severity and upregulated ICAM-1 on conjunctival fibroblasts, suggesting the role of IFNγ in the inflammatory phase of chronic allergic eye diseases.
KeywordsAllergic conjunctivitis Tears Th2 cytokines Interferon-γ
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