Levels of 17 immune-system proteins seem to correlate with the severity of symptoms experienced by people with chronic fatigue syndrome (CFS), also called myalgic encephalomyelitis (ME).
Mark Davis at Stanford University School of Medicine in California and his colleagues searched for markers of inflammation in people with CFS, who often experience flu-like symptoms. The authors measured levels of dozens of immune-system proteins called cytokines in blood samples from 192 patients with CFS and compared them with those from 392 healthy controls. Overall, levels were broadly similar in both groups. However, when the researchers split the cases of CFS into mild, moderate and severe, they found that 17 cytokines, including pro-inflammatory proteins such as interleukin-4 and leptin, tracked the severity of the disease.
The authors suggest that this variation between people with severe and milder states of the disease may explain why some earlier studies failed to distinguish patients from healthy people.