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The role of indoleamine 2,3-dioxygenase in retinal pigment epithelial cell-mediated immune modulation
Choul Yong Park1, Seung-Ha Yang, Roy S Chuck
1Department of Ophthalmology, Dongguk University, School of Medicine, Koyang, South Korea.
Purpose:
To evaluate the role of indoleamine dioxygenase (IDO) in human retinal pigment epithelial cell (RPE)-mediated immune modulation.
Methods:
The immunosuppression of cultured human RPEs (ARPE-19 cells) was assayed using the mixed lymphocyte reaction (MLR) harvested from CBA/J and BALB/c mice. The expression of critical immune modulatory molecules, such as class II major histocompatibility complex (MHC) molecules, co-stimulatory molecules (B7-1 and B7-2), and indoleamine dioxygenase (IDO), was examined by reverse transcriptase polymerase chain reaction, flow cytometry, and immunofluorescence staining with and without IFN-gamma stimulation.
Results:
RPEs expressed IDO and class II MHC molecules under IFN-gamma stimulation. However, B7-1 and B7-2 were not expressed. RPE significantly suppressed MLR in the absence of IFN-gamma prestimulation. This phenomenon was enhanced by IFN-gamma stimulation. The addition of 1-methyl tryptophan (1-MT) into the culture medium successfully reversed RPE immunosuppression.
Conclusions:
The expression of IDO may in part explain RPE-mediated immune suppression effects.
