[Neopterin: a marker used for monitoring infections]

Neopterin released by monocytes/macrophages upon activation by interferon-gamma secreted from T-lymphocytes, is a sensitive indicator of cell-mediated immune activation. Chemically, neopterin is a pyrazino-pyrimidine derivative, namely, 2-amino-4 hydroxy-(1',2',3' trihydroxypropyl)-pteridine. Biosynthetically, neopterin derives from guanosine triphosphate (GTP), and is a biologically stable cytokine. Increased concentrations of neopterin in serum and urine have been found in various infections (especially viral), autoimmune diseases, malignant disorders, and during allograft rejection episodes. In addition, there is a close relationship between high neopterin levels and systemic inflammatory diseases, septicemia and surgical stress. Measurement of neopterin concentration in human body fluids such as serum, urine, cerebrospinal fluid and pleural fluid, allows insight into a cell-mediated immune response. In recent years neopterin becomes an important laboratory parameter for clinical and therapeutical follow-up of diseases involving the cellular immune system. In this review article, the clinical use of neopterin as a marker in the diagnosis and monitorization of the infectious diseases has been discussed.