Research into chronic fatigue syndrome (CFS) got a big boost last month when doctors announced they'd found a simple, reliable blood test for the illness that looks for changes in patients' immune systems—specifically, low levels of immune-system transmitters called cytokines. Now, those same doctors report similar signs in patients' cerebrospinal fluid—a finding that may finally pave the way to treatments for a disease that until recently has been tough to diagnose, let alone treat.
Cytokines play a central role in the immune system's response to viruses and bacteria, and to the inflammation those pathogens cause, but they're also vital for normal brain function, the study's lead author Mady Hornig explains in an email. "We know that cytokines such as interleukin-1 are important in laying down memories and other aspects of cognition."
So it was big news when Hornig and her colleagues discovered low cytokine levels in blood samples of patients with chronic fatigue syndrome—more properly called myalgic encephalomyelitis (ME)—who'd had the illness for more than three years, suggesting doctors could use cytokines as the basis for a blood test. And if researchers found low levels of cytokines in cerebrospinal fluid as well, it might explain why people with ME/CFS often experience neurological symptoms such as impaired memory and have difficulty thinking clearly.
"With this solid foundation, there is now hope that we will soon be able to translate these findings into tangible options that can fill clinicians’ currently-bare toolkits."
To begin to test that idea, Hornig and her team looked at cerebrospinal fluid from 32 patients with ME/CFS, 19 healthy subjects, and 40 patients with multiple sclerosis, which shares some symptoms with ME/CFS. To ensure a strong comparison, the researchers matched the three pools of participants so they had the same proportion of males and females and similar age profiles. Then, they measured 51 separate cytokine levels, revealing a pattern of cytokine interruptions in cerebrospinal fluid similar to what they'd found in blood.
"One of the key advances of our recent work has been to establish that there are clear biological correlates in ME/CFS. Additionally, these findings suggest an immune basis to the disease," Hornig writes. "With this solid foundation, there is now hope that we will soon be able to translate these findings into tangible options that can fill clinicians’ currently-bare toolkits: objective diagnostic tests for disease, and therapies that can correct the imbalance in cytokine levels that we have seen in people with ME/CFS."
The researchers have a lot more on their plate, though. In addition to a study that will track the immune systems of patients with ME/CFS over time, Hornig and her colleagues are also working on detailing the bacteria in the throats and guts of both healthy people and those with ME/CFS, looking at metabolic responses to the disease, and conducting further studies of cerebrospinal fluid. "We are also taking a deeper dive than before in order to discover the potential pathogens that may still be lurking inside the peripheral immune cells of individuals with ME/CFS," Hornig writes.
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