Neopterin: a review.

Neopterin was discovered in bee larvae, in worker bees and in royal jelly. The compound was termed "neopterin" to denote that it might start a new (Greek, neo) epoch in pteridine research. Increased concentrations of neopterin were reported in patients with viral infections, suggesting that increased neopterin may originate from the immune response of patients to the infections. In vitro studies revealed that human monocytes/macrophages produce neopterin when stimulated by interferon-gamma. Neopterin can easily be detected in serum and urine. The most important clinical applications for the determination of neopterin are prognostic indicator of malignant diseases, follow-up control of chronic infections, monitoring of immune-stimulatory therapy, differential diagnosis of acute viral and bacterial infections, prognostic indicator in HIV infections and early indications of complications in allograft recipients. In recent years new physiological functions of neopterin have been discovered such as inducing or enhancing cytotoxicity, inducing apoptosis and the role of a chain breaking antioxidant. This review will focus on the immunological and physiological properties of neopterin.