T-cell cytokines in chronic allergic eye disease

Background: The pathophysiology of chronic allergic eye disease cannot be explained by type I hypersensitivity alone, and T cell-mediated inflammation has been strongly implicated as a possible additional mechanism. Previous studies suggested that T-H2-like T cells play an important role in one form of chronic allergic eye disease. Objectives: This study examined the cytokine profile of T cells in different clinical groups of subjects with chronic allergic eye disease (i.e., vernal keratoconjunctivitis [VKC], atopic keratoconjunctivitis [AKC], and giant papillary conjunctivitis [GPC]) and normal control subjects. Methods: In situ hybridization was used to identify cytokine messenger RNA (mRNA), and two-color immunohistochemical analysis was used to demonstrate cytokine immunoreactivity localizing to T cells in the conjunctiva. Results: Allergic tissue expressed increased levels of mRNA for IL-3, IL-4, and IL-5 when compared with normal tissue. There was significantly greater IL-2 mRNA expression in subjects with AKC than in those with VKC (p = 0.004) and those with GPC (p = 0.02). Immunoreactivity for T-cell IL-5 was present more frequently in subjects with VKC (p = 0.004), GPC (p = 0.02), and AKC (p = 0.04) than in normal control subjects. However, T-cell IFN-gamma protein expression was greater in subjects with AKC than in subjects with VKC (p = 0.01), GPC (p = 0.01), and control subjects (p = 0.005). Conclusions: These results show a T-H2-like T-cell cytokine array in subjects with VKC and GPC but a shift in cytokine profile toward a T-H1-like pattern, potentially because of differences in chronicity of the disorders, in subjects with AKC. These important functional T-cell variations in chronic allergic eye conditions are likely to be important in understanding differences in clinical characteristics and therapeutic responses.