Immune factors in narcolepsy.

Most but not all subjects with the narcoleptic syndrome have the human leukocyte antigen (HLA) DR2 (and DQ1). The narcolepsy-DR2 association is the highest disease-HLA linkage known, and occurs in nonfamilial as well as familial cases of the narcoleptic syndrome. In other forms of daytime drowsiness, there is no relationship with a specific HLA, although some subjects considered to have "essential" hypersomnolence probably have the narcoleptic syndrome. The cause of the narcoleptic syndrome remains unknown, although in a few instances the condition follows infection. There is no evidence for a circulating sleep factor in the blood or in the cerebrospinal fluid of narcoleptic subjects, and no unequivocal marker of cellular immunity has yet been found. However, a few subjects with the narcoleptic syndrome have oligoclonal bands or raised immunoglobulin concentration in the cerebrospinal fluid. It is highly likely that the narcoleptic syndrome is an immune-mediated disorder, occurring in a genetically susceptible (DR2/DQ1-positive) subject.