Decreased IL-27 expression in association with an increased Th17 response in Vogt-Koyanagi-Harada disease

IL-27 has emerged as an important regulator of proinflammatory T-cell responses in animal models. We investigated the pathophysiological role of IL-27 in Vogt-Koyanagi-Harada (VKH) disease.

IL-27P28 and EBI3 mRNA expression in peripheral blood mononuclear cells (PBMCs) were assayed by RT-PCR. Cytokines in the serum and supernatants of PBMCs, naïve CD4(+) T cells and DC-T cocultures were assayed by ELISA. Flow cytometry was used to evaluate the frequencies of IL-17-producing CD4(+) T cells.

The active VKH patients showed a decreased IL-27P28 mRNA expression in PBMCs and lower IL-27 expression in the serum and supernatants of PBMCs, but higher Th17 cells in PBMCs. EBI3 mRNA expression was not different among the groups tested. Stimulation of naïve CD4(+) T cells under Th17 polarizing conditions showed a higher Th17 cell differentiation in active VKH patients. IL-27 significantly inhibited Th17 cell differentiation. IL-27-treated DCs showed a significant inhibition on Th17 differentiation. There was a significant defect in the Tr1 cell induction as measured by IL-10 in active VKH patients. Treatment with corticosteroids and cyclosporine A (CsA) resolved the intraocular inflammation in association with an upregulation of IL-27 and a downregulation of IL-17. In vitro experiments showed that corticosteroids, but not CsA, significantly upregulated the expression of IL-27.

The present study suggests that decreased IL-27 expression may result in a higher Th17 in active VKH patients, which may promote the autoimmune response observed in these patients. Manipulation of IL-27 may offer a novel target for treatment of this disease.