Activated CD4+ T cells, mast cells and eosinophils are the main cytokine-producing cell-types infiltrating the conjunctiva during chronic allergic eye diseases. Interactions between these cells are thought to play an important immunopathogenic role in these disorders (giant papillary conjunctivitis; vernal keratoconjunctivitis; atopic keratoconjunctivitis).
The objective was to compare the cytokine profiles of conjunctival T-cell lines from patients with different forms of chronic allergic eye disease.
T cells were isolated from conjunctival biopsies and non-specifically expanded into lines. The lines were immunophenotyped by flow cytometry. Cytokine production was quantified by immunoassays and more sensitive molecular techniques were used to investigate cytokine mRNA expression to identify the presence of interleukin (IL) -2, IL-4 and interferon (IFN) -γ transcripts.
Following four to six rounds of stimulation, the conjunctival T-cell populations were CD3+ (> 93%), with variable levels of CD4 and CD8 expression. All were HLA-DR+ (> 80%) with some HLA-DQ expression. Conjunctival T-cell lines from atopic keratoconjunctivitis produced selective increases in IFN-γ, IL-10 and IL-13 (P < 0.01), those from vernal keratoconjunctivitis produced increased IL-5 (P < 0.01) whereas T-cell lines from giant papillary conjunctivitis produced only low levels of cytokines. IL-4 was only detected at the mRNA level and was expressed in four out of five T-cell lines in the vernal keratoconjunctivitis group. In contrast there was moderate to strong expression of IFN-γ in five out of six T-cell lines in atopic keratoconjunctivitis.
Different patterns of T-cell cytokine profiles were observed for each disease, with low-level, non-polarized cytokine production in giant papillary conjunctivitis, a TH2-like profile in vernal keratoconjunctivitis and a shift towards a TH1-like profile in atopic keratoconjunctivitis.