Narcoleptics may have an immune disease.

Narcoleptics may have an immune disease

They sleep fitfully at night, drop off unexpectedly during the day, and sometimes fall slumbering face first into their plates at mealtimes. The exact cause of the disorder, called narcolepsy, has eluded researchers so far, but a California group now suggests the problem may involve a defect in one of the genes that control the immune system.

A team led by Emmanuel Mignot of Stanford University School of Medicine's Sleep Disorders Research Center has uncovered evidence in dogs that narcolepsy arises from a mutation in a gene similar to one that spurs the production of antibodies in humans. They report their results in the April 15 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES.

The immune system has been implicated before in narcolepsy. In 1983, a Japanese study linked the disease with a particular class of cell-surface proteins that enable the immune system to distinguish the body's own tissue from foreign invaders. But subsequent studies found that only 90 percent of narcoleptics carried the protein, suggesting the disease results from more than one factor.

In the new study, the Stanford researchers examined DNA from two inbred families of Dobermans and Labradors, roughly half of which had narcolepsy. Two-thirds of the narcoleptic dogs had pieces of DNA that matched human DNA known to control the production of antibodies.

Mignot suggests that the dogs' DNA could be part of a mutant antibody gene. Antibodies made by such a gene, he theorizes, could contribute to narcolepsy by interfering with unidentified cells or molecules necessary for healthy sleep.

Narcolepsy researcher Shiva M. Singh, from the University of Western Ontario in London, Ontario, believes Mignot's group could be on the right track. "There is probably more than one genetic cause for narcolepsy'" he says.