Increased CSF sulfatide levels and serum glycosphingolipid antibody levels in healthy siblings of multiple sclerosis patients

A proportion of healthy siblings of multiple sclerosis (MS) patients have an oligoclonal immunological reaction in their cerebrospinal fluid (CSF) termed the “MS oligoclonal trait”. The CSF levels of the major myelin glycosphingolipid sulfatide and serum antibodies against the glycosphingolipids sulfatide and galactosylceramide were recently reported to be increased in MS patients. We studied the levels of these substances in pairs of 46 patients and their 46 healthy siblings and 50 unrelated healthy blood donors (HBD). The sulfatide concentration in CSF was assayed by thin layer chromatography and immunostaining, and the concentration of galactosylceramide by densitometry after thin layer chromatography. Anti-glycosphingolipid antibody levels were assayed by ELISA. In the healthy siblings, the CSF sulfatide concentrations were markedly increased (p < 0.001, age adjusted p = 0.025), and the serum IgM anti-GalCer antibodies were increased in healthy siblings compared with HBD (p = 0.02). The increased sulfatide or antibody levels did not co-segregate with the “MS oligoclonal trait” or the HLA-DR15 phenotype. In conclusion, a proportion of healthy siblings of MS patients have increased CSF sulfatide and anti-glycosphingolipid antibody levels, which may, analogous to the “MS oligoclonal trait”, constitute an “MS glycosphingolipid endophenotype”. Endophenotypes could potentially simplify the genetics of complex disorders.