Trichloroacetic acid-triggered reaction of kynurenine with nitrite produced by bone marrow-derived myeloid dendritic cells stimulated with CpG

Indoleamine 2,3-dioxygenase (IDO)-initiated tryptophan (Trp) metabolism along the kynurenine (Kyn) pathway regulates T cell responses. However, it is not clear whether bone marrow-derived myeloid dendritic cells (BMDC) express functional IDO. In this study, BMDC expressed IDO protein with nitric oxide (NO) production by CpG oligodeoxynucleotides (CpG), and the CpG-mediated induction of IDO activity in BMDC was severely down-regulated by NO. The error in the estimation of Kyn assay was induced by the reaction of Kyn with nitrite under acidic conditions.