Abstract
Abstract: :
Purpose: To examine expression and functional activity in cornea of the immunoregulatory enzyme indoleamine 2,3 dioxygenase (IDO). Methods: Cultured corneal endothelial cells and homogenized whole mouse corneas were analysed by RT–PCR and western blotting for IDO mRNA and protein. Immunohistochemistry was used to localise IDO expression in corneal sections. To examine functional activity of IDO, (i) an assay for L–kynurenine, the breakdown product of tryptophan following degradation by IDO, and (ii) specific blockade by the IDO inhibitor 1–MT were used . Results: Minimal IDO mRNA and protein were found on analysis of normal murine corneal endothelial cells in vitro and whole cornea. Clear upregulation was found following stimulation with cytokines IFNg and/or TNF. Protein expression was localised to endothelium in tissue sections. Expressed IDO was functionally active, as determined by tryptophan degradation and inhibition by 1–MT. IDO mRNA expression in corneal allografts increased at intervals following transplantation until time of rejection onset. IDO overexpression by lentivirus–mediated IDO cDNA transfer to donor corneas resulted in extended survival in allogeneic recipients following orthotopic transplantation. Conclusions: IDO has a number of possible immunoregulatory roles in conreal endothelium and the anterior chamber, notably in corneal transplantation.
Keywords: cornea: basic science • cornea: endothelium • transplantation