BACKGROUND The indoleamine, 2-3 dioxygenase (IDO) is an inducible intracellular enzyme with immunosuppressive effects mainly on lymphocyte populations. It has been postulated that indirect determination of IDO serum activity may be a marker of renal graft rejection, but its potential usefulness in heart transplantation (HT) is unknown. METHODS This longitudinal study included 98 HT patients (...

Immunotherapy can paradoxically up-regulate immunosuppressive pathways, a phenomenon we term “rebound immunosuppression”. One such pathway is the immunosuppressive enzyme indolamine-2,3-dioxygenase (IDO). Here, we postulated that IDO blockade will improve immunotherapy efficacy by preventing rebound immune-suppression. It has been previously shown that immunotherapy consisting of intralesional ...

Dendritic cells (DCs) express the immunoregulatory enzyme IDO in response to certain inflammatory stimuli, but it is unclear whether DCs express this enzyme under steady-state conditions in vivo. In this study, we report that the DCs in mesenteric lymph nodes (MLNs) constitutively express functional IDO, which metabolizes tryptophan to kynurenine. In line with a previous report that regulatory ...

Indoleamine 2,3-dioxygenase (IDO) metabolizes L-tryptophan to L-kynurenine, promotes immunosuppression, and has been described as a consumer of superoxide. We discovered IDO expression in periaortic fat and tested the hypothesis that periarterial IDO functionally reduces agonist-induced contraction. Our model was the thoracic aorta, abdominal aorta, and superior mesenteric artery of the male Sp...

Atherosclerosis is the major cause of cardiovascular disease (CVD), the leading cause of death worldwide. Despite much focus on lipid abnormalities in atherosclerosis, it is clear that the immune system also has important pro- and antiatherogenic functions. The enzyme indoleamine-2,3-dioxygenase (IDO) catalyses degradation of the essential amino acid tryptophan into immunomodulatory metabolites...

Background There is no biomarker for diagnosing active tuberculosis in patients with human immunodeficiency virus (HIV) infection. Indoleamine 2, 3-dioxygenase (IDO) is an immunoregulatory enzyme that breaks down tryptophan (Trp) to metabolites known as kynurenines (Kyns). We investigated whether IDO activity, as measured by the ratio of Kyn to Trp, could be used to diagnose or predict active t...

This paper addresses the use of dispositions in the Infectious Disease Ontology (IDO). IDO is an ontology constructed according to the principles of the Open Biomedical Ontology (OBO) Foundry and uses the Basic Formal Ontology (BFO) as an upper ontology. After providing a brief introduction to disposition types in BFO and IDO, we discuss three general techniques for representing combinations of...

Activation of the tryptophan catabolizing enzyme indoleamine 2,3-dioxygenase (IDO) in cancer cells facilitates immune escape. A recent study now shows how small-molecule inhibitors of IDO can be used to leverage the efficacy of traditional chemotherapeutic drugs that are used to treat cancer in the clinic. By promoting antitumor immune responses in combination with cytotoxic chemotherapy, IDO i...

Small-molecule inhibitors of indoleamine 2,3-dioxygenase (IDO) are currently being translated to clinic for evaluation as cancer therapeutics. One issue related to trials of the clinical lead inhibitor, D-1-methyl-tryptophan (D-1MT), concerns the extent of its biochemical specificity for IDO. Here, we report the discovery of a novel IDO-related tryptophan catabolic enzyme termed IDO2 that is pr...

The tryptophan catabolic enzyme indoleamine 2,3-dioxygenase (IDO) has emerged as an important driver of immune escape in a growing number of cancers and cancer-associated chronic infections. In this study, we define novel immunotherapeutic applications for the heme precursor compound zinc protoporphyrin IX (ZnPP) based on our discovery that it is a potent small-molecule inhibitor of IDO. Inhibi...