Abstract

Aims To determine whether an active metabolite of vitamin A, all-trans retinoic acid (ATRA), reduces inflammation in experimental autoimmune uveoretinitis (EAU).

Methods Naive CD4⁺ T cells were activated with anti-CD3, anti-CD28 and transforming growth factor (TGF)-β, in the presence or absence of ATRA. Intracellular expression of transcription factor forkhead box P3 (Foxp3) and interleukin (IL)-17 in the activated CD4⁺ T cells was assessed by flow cytometry. C57BL/6 mice were immunised with human interphotoreceptor retinoid binding protein peptide 1–20 (IRBP_1–20). ATRA was administered intraperitoneally every other day (0.2 mg/mouse per day) from day 0 to day 21. In vivo-primed draining lymph node cells from vehicle-treated or ATRA-treated mice were stimulated with IRBP_1–20 and the culture supernatant fraction was harvested for assay of interferon (IFN)-γ and IL-17 by ELISA.

Results ATRA synergised with TGF-β to induce Foxp3⁺ T regulatory cells (Treg) and reciprocally inhibited development of IL-17-producing T helper cells (Th17) induced by TGF-β and IL-6. ATRA treatment reduced the severity of EAU clinically, and IFN-γ and IL-17 production were significantly reduced in ATRA-treated mice.

Conclusion These findings demonstrate that ATRA treatment ameliorates severity of EAU and reduces the Th1/Th17 responses. ATRA may represent a new therapeutic modality for human refractory uveitis.