[Clinical usefulness of neopterin].

Neopterin (NPT) concentration reflects the activation of the cellular immune system. Neopterin is released by macrophages stimulated by interferon gamma which is produced by activated T lymphocytes. Raised NPT concentrations in body fluids are found in various disorders, e.g., viral infections, infections caused by intracellular bacteria, autoimmune disorders and malignancy. Neopterin concentration is low or not significantly high in bacterial infections (except for induced by intracellular bacteria).