An immune system gene has been strongly associated with a form of narcolepsy, lending strength to the long-held belief that this sleep disorder is an autoimmune disease. The researchers suggest that this finding could have implications not just for narcolepsy, but for a wide range of autoimmune diseases. The gene is TCRA (T-cell receptor alpha), which codes for a receptor protein on T-cells. Narcolepsy is a disorder that causes disabling daytime sleepiness, irresistible bouts of sleep that can strike at any time, and disturbed sleep at night. This new study focused on a special form of the disease called narcolepsy with cataplexy, which is a sudden loss of muscle tone that can cause a person to collapse, with or without falling asleep. Approximately 1 in 2,000 people in the United States have narcolepsy-cataplexy. The symptoms of this disease have been shown to result from the death of a small group of brain cells that normally regulate the sleep-wake cycle by releasing hormone chemicals called hypocretins. Previous work had shown that almost everyone with narcolepsy-cataplexy has the same variant (HLA-DQB*0602) of a major histocompatibility gene. Because of HLA’s prominent role in immunity, it was hypothesized that narcolepsy-cataplexy might be caused by an autoimmune attack on the hypocretin-producing cells in the brain. The new study lends credence to this theory by implicating an immune system gene (TCRA).
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