Studies of humoral immunity to preprohypocretin in human leukocyte antigen DQB1*0602-positive narcoleptic subjects with cataplexy.
BACKGROUND
Canine models for narcolepsy have mutations of the hypocretin receptor 2 gene, and preprohypocretin knockout murine lines exhibit narcoleptic-like behaviors. Human narcolepsy with cataplexy is associated with human leukocyte antigen DQB1*0602 and reduced hypocretin levels in cerebrospinal fluid, suggesting an autoimmune diathesis. We tested the hypothesis that DQB1*0602-positive narcoleptic subjects with cataplexy have immunoglobulin (Ig)G reactive to human preprohypocretin and its cleavage products.


METHODS
Serum samples of 41 DQB1*0602-positive narcoleptic subjects with cataplexy and 55 control subjects were studied, as were 19 narcoleptic and 13 control samples of cerebrospinal fluid. We tested for IgG reactive to preprohypocretin and its major cleavage products (including hypocretin 1 and 2), using immunoprecipitation assays (IP), immunofluorescence microscopy (IF) of Chinese hamster ovarian cells expressing preprohypocretin, and Western blots.


RESULTS
There was no evidence for IgG reactive to preprohypocretin or its cleavage products in CSF of subjects with narcolepsy as measured by IPs, Western blots, and IF. Although the IP with CSF and the C-terminal peptide showed significant differences by two methods of comparison, the control subjects had higher counts per minute than narcoleptic subjects, which was opposite to our hypothesis.


CONCLUSIONS
The hypothesis that DQB1*0602-positive narcoleptic subjects with cataplexy have IgG reactive to preprohypocretin or its cleavage products was not supported.
Black
John L
JL
Psychogenomics Laboratory, Department of Psychiatry and Psychology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA. black.john@mayo.edu
Silber
Michael H
MH
Krahn
Lois E
LE
Avula
Rajeswari K
RK
Walker
Denise L
DL
Pankratz
V Shane
VS
Fredrickson
Paul A
PA
Slocumb
Nancy L
NL
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000917:Antibody Formation / Q000502:physiology*; D015153:Blotting, Western / Q000379:methods; D002352:Carrier Proteins / Q000134:cerebrospinal fluid*; D002385:Cataplexy / Q000150:complications / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique / Q000379:methods; D006683:HLA-DQ Antigens / Q000276:immunology* / Q000378:metabolism; D059866:HLA-DQ beta-Chains; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D047908:Intracellular Signaling Peptides and Proteins / Q000134:cerebrospinal fluid; D008297:Male; D008562:Membrane Glycoproteins / Q000276:immunology* / Q000378:metabolism; D008875:Middle Aged; D009290:Narcolepsy / Q000150:complications / Q000235:genetics / Q000378:metabolism*; D009479:Neuropeptides / Q000134:cerebrospinal fluid; D000068797:Orexins
D002352:Carrier Proteins; C000596229:HCRT protein, human; D006683:HLA-DQ Antigens; D059866:HLA-DQ beta-Chains; C069051:HLA-DQB1 antigen; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D009479:Neuropeptides; D000068797:Orexins