Used in biomedical research to measure indoleamine 2,3-dioxygenase (IDO) activity in human samples. Helps assess immune responses, as IDO plays a key role in regulating inflammation and immune tolerance. Commonly applied in studies of cancer, autoimmune diseases, pregnancy, and infectious diseases. Enables researchers to evaluate the effectiveness of IDO inhibitors in drug development and immunotherapy. Provides a reliable, sensitive method for quantifying IDO activity in cell cultures, serum, and plasma.