Increased neopterin concentrations are established in patients with an activated cellular (= Th1-type) immune response which includes allograft rejection, viral infection and autoimmune disorders as well as various malignant tumors. In patients with several types of cancer, neopterin concentrations in body fluids like urine, serum/plasma or ascites parallel the course of the disease, and a higher neopterin concentration in patients is an independent predictor of a shorter survival period. Neopterin is released in large amounts from human monocyte-derived macrophages and dendritic cells preferentially following stimulation with the pro-inflammatory cytokine interferon-gamma, thus reflecting the immune activation status. Therefore, not only as a laboratory diagnostic tool, the measurement of neopterin concentrations allows studying the immunological network and its interaction with the pathogenesis of tumor development. It contributes to a better understanding how immune activation is involved in the development of tumor-induced immune escape and tumor antigen specific tolerance.
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