Indoleamine 2,3-dioxygenase 2 (IDO2) is related to IDO1/IDO, and may play a role in T and B cell immunity. IDO2 is not as widely expressed as IDO, but like its relative, it is also expressed in antigen-presenting dendritic cells where tryptophan catabolism drives immune tolerance. Like IDO, IDO2 catabolizes tryptophan, triggers phosphorylation of the translation initiation factor eIF2alpha, and mobilizes translation of LIP, an inhibitory isoform of the immune regulatory transcription factor NF-IL6 (nuclear factor for interleukin-6).