The importance of neopterin as a laboratory diagnostic marker of immune activation

Neopterin is produced and secreted in large amounts by interferon-g stimulated human monocytes/macrophages. Neopterin measurement in urine and serum provides a useful possibility to estimate the degree of cellular (Th1-type) immune activation, which is directed against viral infections, intracellular bacteria, and certain parasites. Also in malignancy, autoimmune diseases and allograft rejection episodes neopterin sensitively relfects the extent of cellular immune activation. Determination of neopterin concentrations can be conveniently performed by immunoassay like ELISA or RIA, and HPLC. The major diagnostic applications of neopterin monitoring are: surveillance of the immune status of organ recipients, therapy control and prognosis of disease progression in tumor diseases and HIV infections and also detection of unknown infections in e.g. blood banks. High neopterin levels are strongly associated with oxidative stress, opening an additional application field of neopterin monitoring to estimate the extent of tissue damage in the course of immune activation.