Complement C4a

Complement C4a is a protein that is expressed, primarily in the liver and in macrophages, in response to acute inflammation or tissue injury. Increased C4a levels have been found one to six hours after exercise challenge tests in ME/CFS patients and not in healthy controls. Others found a strong relation between the change in complement C4a level and an increase in post-exertional pain and fatigue in ME/CFS patients. Previously, complement C4a, in combination with other proteins, was being considered as a potential marker of post-exertional malaise in ME/CFS.