IDO (D5J4E™) Rabbit mAb (PE Conjugate)

INDO/IDO1/indoleamine 2,3-dioxygenase (IDO) is an IFN-γ-inducible enzyme that catalyzes the rate-limiting step of tryptophan degradation (1). IDO is upregulated in many tumors and in dendritic cells in tumor-draining lymph nodes. Elevated tryptophan catabolism in these cells leads to tryptophan starvation of T cells, limiting T cell proliferation and activation (2). Therefore, IDO is considered an immunosuppresive molecule, and research studies have shown that upregulation of IDO is a mechanism of cancer immune evasion (3). The gastrointestinal stromal tumor drug, imatinib, was found to act, in part, by reducing IDO expression, resulting in increased CD8+ T cell activation and induction of apoptosis in regulatory T cells (4). In addition to its enzymatic activity, IDO was recently shown to have signaling capability through an immunoreceptor tyrosine-based inhibitory motif (ITIM) that is phosphorylated by Fyn in response to TGF-β. This leads to recruitment of SHP-1 and activation of the noncanonical NF-κB pathway (5). 1.Yasui, H. et al. (1986) Proc Natl Acad Sci U S A 83, 6622-6. 2.Mellor, A.L. et al. (2003) Adv Exp Med Biol 527, 27-35. 3.Prendergast, G.C. (2008) Oncogene 27, 3889-900. 4.Balachandran, V.P. et al. (2011) Nat Med 17, 1094-100. 5.Pallotta, M.T. et al. (2011) Nat Immunol 12, 870-8.