IL-10 and TGF-β Immunoregulatory Cytokines rather than Natural Regulatory T Cells are Associated with the Resolution Phase of Vogt-Koyanagi-Harada (VKH) Syndrome

The pro-inflammatory cytokines play a critical role in the initiation and propagation of ocular autoimmune diseases. Regulation of these cytokines is generally mediated by the immunoregulatory cytokine such as IL-10 or TGF-beta. In this study, we investigated the immunoregulatory cytokine profile and frequency of natural regulatory T cells (nTregs) in patients with Vogt-Koyanagi-Harada (VKH). We obtained the peripheral blood mononuclear cells (PBMC) from patients with VKH and healthy controls. The cytokine profile from supernatants of PBMC cultured with or without phytohaemagglutinin (PHA) was measured by ELISA, the percentage of CD4+ Foxp3+ and CD25highFoxp3+ T regulatory cells were analysed by flow cytometry, and the transcriptional level of Foxp3 expression was analysed by real-time quantitative PCR. The immunoregulatory cytokines, TGF-beta and IL-10, increased in patients with VKH in the inactive stage of the disease. We observed no significant difference in the CD4+ Foxp3+ and CD25highFoxp3+ T cells as well as no reduction in FOXP3 mRNA expression in the patients with VKH when compared to healthy controls. We showed in our work, an increase in IFN-gamma secretion by PBMC of patients with VKH in the active stage of the disease when compared to healthy controls and patients in the inactive stage. Our data suggest that IL-10 and TGF-beta cytokines, rather than nTregs are associated with the resolution phase of the disease and may have a more relevant role in controlling this disease.