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Background: Thymic expression of a photoreceptor cell antigen, interphotoreceptor retinoid-binding protein, is known to generate regulatory T cells (Treg) that prevent spontaneous autoimmune disease of the retina. However, the contribution of other endogenous, tissue-specific antigens (Ags) expressed in the retina to the generation of Treg is uncertain. Methods: Transgenic mice that express β-galactosidase (β-gal) in photoreceptor cells, together with β-gal-specific T cell receptor transgenic mice, were used to study the induction of Treg in vivo. Results: Transgenic expression of β-gal on the arrestin promoter led to a spontaneous immunoregulatory response that inhibited the development of immune responses to β-gal. The regulation was transferred by CD3+4+25+ Treg. Several strategies were then used to show that β-gal expressed in the retina supported spontaneous, thymus-independent Treg development. The endogenous Treg also differed from the Treg induced by Ag inoculation into the anterior chamber of the eye. Conclusion: These results demonstrate that retinal expression of very small amounts of a tissue-specific Ag can generate Treg in the periphery.

The hexose monophosphate shunt inhibitor 6-aminonicotinamide was observed to have an anti-inflammatory effect in the treatment of experimental uveitis. The electrons required for the reduction of molecular oxygen to superoxide radicals are generated by the pentose phosphate pathway in acute inflammatory cells. The inhibition of superoxide production is discussed as one of the potential antiphlogistic mechanisms.