Description_x000D_ General description_x000D_ Indoleamine 2,3-Dioxygenase 1 (IDO1) is a cytoplasmic hemoprotein that oxidizes tryptophan yielding N-formylkynurenine (NFK). In mammals, this reaction is the first and rate limiting step in the kynurenine catabolic pathway. IDO1 activity is low under normal physiological conditions, but is dramatically upregulated by proinflammatory cytokines such as interferon-γ. This short-term activation of IDO1 occurs as part of the innate immune response and helps to inhibit the growth of pathogens and parasites. IDO1 activation can also promote host immune tolerance by exerting an immunosuppressive effect. IDO1 expression by tumor cells play a substantial role in tumor immune tolerance, aiding tumors in evading detection and destruction. Chronic induction of IDO1 expression has been found in cancer patients and is correlated with negative prognosis. IDO1 has thus become an attractive pharmacological target for development of novel antineoplastics and adjuvants to increase the efficacy of conventional chemotherapy._x000D_ Features and Benefits_x000D_ Compatible with high-throughput handling systems._x000D_ Suitability_x000D_ Suitable for the assessment of native or recombinant IDO1 activity and the screening of drugs and novel ligands for induction or inhibition of cellular IDO1 activity in mammalian tissues expressing IDO1, cultured cells treated with IDO1-inducing cytokines (e.g. interferon-γ), recombinant IDO1 enzyme preparations, and IDO1-expressing heterologous cells._x000D_ Principle_x000D_ The Indoleamine 2,3-Dioxygenase 1 Activity Assay Kit enables IDO1 activity to be easily determined in mammalian tissues and cell lines. The assay uses a fluorogenic developer that selectively reacts with NFK to produce a highly fluorescent product (ex = 402 nm/em = 488 nm), ensuring a high signal-to-background ratio. The kit also includes a highly selective IDO1 inhibitor for verification of enzyme activity in biological matrices. The assay has a simple no-wash protocol, is high-throughput adaptable and can detect down to 0.2 mU of IDO1 activity or 200 pmole NFK.