IDO1 and IDO2 gene expression analysis by quantitative polymerase chain reaction.

Immunomodulatory properties of IDO1 relate to tryptophan catabolism. The degradation of tryptophan by IDO1 leads to suppression of T cell responses. Recently, another enzyme with IDO-like activity, indoleamine 2,3-dioxygenase-like-protein 1 (INDOL1, IDO2), has been described in both mice and humans. In order to study the gene expression of IDO1 and IDO2, we have developed a quantitative PCR (qPCR) assay. In an exploratory application to the study of the differential expression of IDO1 and IDO2 by professional antigen-presenting cells and MSCs (mesenchymal stromal cells) under the influence of interferon-γ (IFN-γ) and T-lymphocyte conditioned media (TCM), substantial differences were observed. IDO expression measured by qPCR was valid and reliable in the cell types investigated. Further studies are needed to delineate factors driving IDO expression in MSCs.