Indoleamine 2,3-dioxygenase (IDO), an enzyme that degrades the essential amino acid l-tryptophan along the kynurenine pathway, exerts immunomodulatory effects in a number of diseases. IDO expression is increased in tumor tissue and in draining lymph nodes; this increase is thought to play a role in tumor evasion by suppressing the immune response. A competitive inhibitor of IDO is currently bei...

Indoleamine 2,3-dioxygenase (IDO), a flavin-dependent enzyme that catalyzes the conversion of tryptophan to kynurenine, is induced in peripheral blood mononuclear cells by interferon-gamma (IFN gamma). Interleukin-4 (IL-4) is a cytokine that modulates the functional properties of monocytes/macrophages, and we investigated the effects of IL-4 on IDO. We showed that IL-4 inhibited the induction o...

Control of pathogens by formation of abscesses and granulomas is a major strategy of the innate immune system, especially when effector mechanisms of adaptive immunity are insufficient. We show in human listeriosis that DCs expressing indoleamine 2,3-dioxygenase (IDO), together with macrophages, are major cellular components of suppurative granulomas in vivo. Induction of IDO by DCs is a cell-a...

BACKGROUND Acquired immunity is impaired in hemodialysis (HD) patients. Indoleamine 2,3-dioxygenase (IDO) is inducible by inflammation and through tryptophan depletion and generation of kynurenine pathway products suppresses adaptive immune response. In the present study plasma IDO levels were assessed in HD patients. Its effect on response to HBV vaccination program was evaluated. PATIENTS A...

Indoleamine 2,3-dioxygenase (IDO) is an immunosuppressive enzyme that contributes to tolerance in a number of biological settings. In cancer, IDO activity may help promote acquired tolerance to tumor antigens. The IDO inhibitor 1-methyl-tryptophan is being developed for clinical trials. However, 1-methyl-tryptophan exists in two stereoisomers with potentially different biological properties, an...

Indoleamine 2,3-dioxygenase (IDO) has been implicated in immune evasion by tumors. Upregulation of this tryptophan (Trp)-catabolizing enzyme, in tumor cells and myeloid-derived suppressor cells (MDSCs) within the tumor microenvironment (TME), leads to Trp depletion that impairs cytotoxic T cell responses and survival; however, exact mechanisms remain incompletely understood. We previously repor...

Human fibroblasts provide immunosuppressive functions that are partly mediated by the tryptophan-catabolizing enzyme indoleamine-2,3-dioxygenase (IDO). Moreover, upon stimulation with inflammatory cytokines human fibroblasts exhibit broad-spectrum antimicrobial effector functions directed against various clinically relevant pathogens and these effects are also IDO-dependent. Therefore human fib...

L-Tryptophan is the least abundant essential amino acid in humans. Indoleamine 2,3-dioxgyenase (IDO) is a cytosolic heme protein which, together with the hepatic enzyme tryptophan 2,3-dioxygenase, catalyzes the first and rate-limiting step in the major pathway of tryptophan metabolism, the kynurenine pathway. The physiological role of IDO is not fully understood but is of great interest, becaus...

BACKGROUND Indoleamine 2,3-dioxygenase (IDO) is a tryptophan catalyzing enzyme. It has been suggested that it has a role in lower airway allergic inflammations, but its role in allergic rhinitis has not been investigated. OBJECTIVE Our aim was to evaluate the expression of IDO in the nasal mucosa of allergic rhinitis patients allergic to birch pollen during peak exposure to birch pollen aller...

The degradation of tryptophan (TRP) along the kynurenine pathway plays a crucial role as a neuro- and immunomodulatory mechanism in response to inflammatory stimuli, such as lipopolysaccharides (LPS). In endotoxemia or sepsis, an enhanced activation of the rate-limiting enzyme indoleamine 2,3-dioxygenase (IDO) is associated with a higher mortality risk. It is assumed that IDO induced immunosupp...