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To evaluate the role of IFN-gamma (interferon gamma) in IL-12- (interleukin-12)-induced inhibition of the inflammatory response in the eye during endotoxin-induced uveitis (EIU). C57BL/6 wild type mice and IFN-gamma-deficient (GKO) mice were injected with 250 microg of Salmonella typhymurium endotoxin as a model for EIU. Animals were then injected intraocularly with 100 ng of rIL-12 or the equivalent volume of Phosphate-buffer saline (PBS). Histopathologic grading of disease was performed 12, 36 and 72 h after endotoxin injection. Chemokine mRNA expression in the eye was evaluated by reverse transcriptase-polymerase chain reaction. Depletion of NK1.1+ cells in vivo was performed using a PK136 antibody. Depletion of IFN-gamma was performed using the R4-6A2 antibody. C57BL/6 mice treated with rIL-12 intraocularly were protected from the development of EIU. Neutralization of IFN-gamma with a monoclonal antibody abrogated such protection. The IL-12 protective effects were lost in NK1.1-depleted mice. Intraocular IL-12 decreased the expression of keratinocyte-derived chemokines (KC) gene but had no effect on macrophage inflammatory protein (MIP-2) gene. The protective effect of IL-12 during EIU occurs through production of IFN-gamma by NK1.1+ cells. IL-12-induced higher levels of IFN-gamma are also correlated with lower expression of the chemokine KC, resulting in diminished attraction of neutrophils to the inflammatory site.

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 CD25(high)Foxp3(+) 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 CD25(high)Foxp3(+) 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.