A press release from The American College of Rheumatology discusses the results of a new study on chronic widespread pain, such as that experienced with fibromyalgia.

Led by Nurcan Üçeyler of Julius-Maximilians University in Wurzburg, Germany, researchers analyzed cytokines in 40 patients with chronic widespread pain (26 of whom had FM), 40 controls and an additional group of 15 patients. The 40 pain patients had received intravenous immunoglobulin (IVIG) as a novel treatment for pain that was not responsive to standard therapy, while the additional 15 patients did not receive this treatment. Blood samples were analyzed for both pro-inflammatory and anti-inflammatory cytokines. In addition, patients were asked to rate their pain, fatigue, mood, cognitive function and sleep quality on a scale of 1 to 10.

An article on About.Arthritis explains:

Study results published in the August 2006 issue of Arthritis & Rheumatism revealed cytokine profiles of 40 patients with chronic widespread pain. Of the 40 patients, 26 had fibromyalgia. Cytokines are proteins which serve as messengers between cells and play a role in the inflammation pathway.

Wikipedia explains cytokines this way:

Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. These chemical signals are similar to hormones and neurotransmitters and are used to allow one cell to communicate with another.