A specific immune cell has been identified in narcolepsy patients, indicating that the common sleep disorder is in fact an autoimmune disease. This finding, and a further understanding of the specific mechanisms that cause narcolepsy, could serve as a model for other autoimmune diseases, such as type 1 diabetes, multiple sclerosis and Crohn´s disease.
Autoimmune diseases are characterized by overactive, and often aggressive, immune responses, to natural substances in the body. This often results in cell, and eventually organ, damage. For example, in type 1 diabetes, also known as juvenile diabetes, insulin-producing beta cells within the pancreas are attacked and destroyed by the immune system, resulting in an inability to control blood glucose levels.
Narcolepsy is a common (effects approximately one in 2,000 individuals), but generally poorly understood sleep disorder. Irregular sleeping and daytime fatigue are two of the most common symptoms, along with a “sudden loss of muscle tone and strength,” known as cataplexy.
More than 10 years ago, the same researchers who published the current study, confirmed that narcolepsy was the result of a lack of the wakefulness inducing hormone hypocretin in the brain, and that narcolepsy patients had lower levels of brain cells that produce this hormone. This finding created the suspicion that narcolepsy was connected to the immune system, but it was not confirmed as an autoimmune disease until now. “For a long time, people have suspected narcolepsy had something to do with the immune system — that it was killing cells that produce hypocretin,” says lead researcher Dr. Emmanuel Mignot.
“Whole-genome scans” were performed on 800 narcoleptics, and 1,800 individuals in total, in the current study. This technique allows researchers to observe a thorough range of gene variations, and was performed based on a suggested connection between a variant of the human leukocyte antigen (HLA) gene, and narcolepsy (all 1,800 participants had this particular genetic variation).
It was observed that in the narcolepsy patients, the variation in HLA was related to T cells, which are immune cells related to immune response. According to Dr. Mignot, this observation “clearly shows narcolepsy is an autoimmune disease.” Dr. Mignot believes that the HLA and T cells work together to attack hypocretin producing brain cells, though the specific mechanisms of this action will need to be confirmed through further research.
In addition to forming a better base for treating narcolepsy, the hope is that an understanding of the autoimmune mechanisms that lead to narcolepsy, will lead to a better understanding of other poorly understood autoimmune diseases, such as those mentioned above. “We’re now getting the main pieces of what’s happening in narcolepsy. What’s most satisfying to me is that we’re bringing this story to a close and that we can use narcolepsy as a model for other diseases. If we can work out what happens specifically in patients with narcolepsy, we’ll be able to better understand the role of T cells in other autoimmune diseases that are more complicated and difficult to detect,” concludes Dr. Mignot.
Source: Defeat Diabetes Foundation: Mignot, Emmanuel. Brandt, Michelle. Stanford University Medical Center news release. May 2009.