Cytokine

Cytokines are any class of immunoregulatory proteins secreted by cells, especially immune system cells. Cytokines are small proteins important in cell signaling that modulate the immune system.

There are many different cytokines. They function as messenger molecules passing information around the body. They resemble hormones in this way, but they are usually communicating in response to something external and lead to inflammatory or immune responses.

Types of cytokines

 * Chemokines
 * Interferons
 * Interleukins
 * Lymphokines
 * Tumor necrosis factor

Cellular immune response
IFN-γ, TNFα

Antibody response
TGF-β, IL-4, IL-10, IL-13

Chronic Fatigue Syndrome
There is increasing evidence that cytokine expression is altered in CFS (ME). Mady Hornig et al (2015) indicates that there is a generally increased response in the first 3 years of illness. In 2017, a Montoya, et al, study showed that "seventeen cytokines had a statistically significant upward linear trend that correlated with ME/CFS severity"..."thirteen of these are proinflammatory, likely contributing to many of the symptoms experienced by patients."

Two large 2015 studies found a general pattern of down regulation in long term patients (Hornig, et al and Landi, et al). It is worth noting that these differences can average each other out when data from newly diagnosed and long term patients are analysed together. More accurate data may necessitate patient groups being stratified by disease duration.

In a 2017 study by Hornig, Lipkin et al, 51 Cytokines of cerebrospinal fluid were measured where they found Atypical and Classical cases of ME/CFS. There are differing immune signatures within the central nervous system. "Typically, symptoms of ME/CFS begin suddenly following a flu-like infection, but a subset of cases classified by the investigators as “atypical” follows a different disease course, either from triggers preceding symptoms by months or years, or accompanied by the later development of additional serious illnesses."

When reading cytokine studies it is important to remember that with so many cytokines it is common to find some pattern and results can change quickly within individuals. In a small sample, if just a couple of people were fighting a cold then this could change the overall results.

Fibromyalgia
Fibromyalgia: Cytokines IL-1beta, IL-6 and TNF-alpha are involved with central and peripheral neuropathic pain which is experienced by Fibromyalgia patients. Profiles are distinguishing Lupus and Rheumatoid Arthritis from Fibromyalgia.

Cytokines and Chemokines
Chemokines are cytokines that induce chemotaxis. Chemotaxis is the orchestrated movement of cells towards a specific location flagged by a chemical messenger. Unlike cytokines, chemokines have just one major role: to direct leukocytes toward pathogens, or to areas of injured/diseased tissue.
 * What is the Difference Between a Cytokine and a Chemokine? (WiseGEEK)

Notable studies

 * 2010, A Formal Analysis of Cytokine Networks in Chronic Fatigue Syndrome - (Full text)
 * 2015, Distinct plasma immune signatures in ME/CFS are present early in the course of illness
 * 2015, Daily cytokine fluctuations, driven by leptin, are associated with fatigue severity in chronic fatigue syndrome: Evidence of inflammatory pathology - (Full text)
 * 2015, Plasma cytokine expression in adolescent chronic fatigue syndrome
 * 2016, Reductions in circulating levels of IL-16, IL-7 and VEGF-A in myalgic encephalomyelitis/chronic fatigue syndrome
 * 2017, Cytokine signature associated with disease severity in chronic fatigue syndrome patients - (Full text)
 * 2017, Cytokine signatures in chronic fatigue syndrome patients: a Case Control Study and the effect of anakinra treatment - (Full text)
 * 2019, The clinical value of cytokines in chronic fatigue syndrome - (Full text)

Learn More

 * HGNC - Official nomenclature for cytokines, chemokines, and growth factors