Neopterin

Neopterin is part of the pteridin class of molecules. Neopterin acts as a marker for immune system activation and neuroinflammation.

Neopterin is found in blood serum, urine, tears, Cerebrospinal fluid.

Neopterin in cerebrospinal fluid has also been suggested as a possible biomarker for flu-associated encephalopathy in children.

Function
Neopterin is also a metabolite of guanosine triphosphate (GTP) that is produced by a type of white blood cell known as macrophages after IFN-γ stimulation.

Research on brains affected by Alzheimer's disease has shown levels of neopterin are five times higher than in healthy brains. Some evidence suggests that microglia may produce neopterin during physiological stress, and that neopterin may have a protective role in response to damage or inflammation.

ME/CFS
Maes et al. (2012) found that levels of lysozyme and neopterin were significantly higher in patients with ME/CFS compared to patients with chronic fatigue and healthy controls.

Notable studies

 * 2012, Evidence for inflammation and activation of cell-mediated immunity in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): increased interleukin-1, tumor necrosis factor-α, PMN-elastase, lysozyme and neopterin. - (Abstract)
 * 2021, The Reification of the Clinical Diagnosis of Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS) as an Immune and Oxidative Stress Disorder: Construction of a Data-Driven Nomothethic Network and Exposure of ME/CFS Subgroups - (Full text)