The immune system has a critical influence on the maintenance of physiological homeostasis. To date, immunological dysfunction, particularly reduced natural killer (NK) cell cytotoxic activity in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) patients has been consistently observed. CFS/ME is a severely debilitating illness, with no known pathomechanism and diagnosis is made according to symptom specific criteria. CFS/ME is characterised by persistent and unexplained fatigue, alongside a range of symptoms, including: post-exertional neuroimmune exhaustion, neurological, immune, gastrointestinal, genitourinary and energy metabolism impairments. However, a symptom specific criterion provides complications for diagnosis, particularly as symptoms may be qualitative. CFS/ME is also a heterogeneous illness, with patients experiencing moderate to severe symptoms. CFS/ME patients with moderate symptoms are those who have reduced mobility and ability to perform their routine daily activities. CFS/ME patients with severe symptoms are usually homebound and/or restricted to a wheelchair. The debilitating nature of CFS/ME creates an economic burden and contributes largely to health resources, affecting CFS/ME patients as well as the wider community. In Australia, the annual cost to the community per CFS/ME patient, with a prevalence rate of 0.2% is $729.3 million (based on 2012 estimates and earlier prevalence studies).