A SENSITIVE TIME-RESOLVED IMMUNOFLUOROMETRIC ASSAY FOR THE MEASUREMENT OF APOLIPOPROTEIN-B IN CEREBROSPINAL-FLUID - APPLICATION TO MULTIPLE-SCLEROSIS AND OTHER NEUROLOGICAL DISEASES

Although low density lipoprotein receptors have been described on olig odendrocytes, apolipoprotein B was thought to be absent or present in only very small amounts in cerebrospinal fluid (CSF). Several immunoas says have been used for the measurement of apolipoprotein B in serum. However, the majority of methods cannot be used to measure small amoun ts of apolipoprotein B in CSF. In this study, we describe a highly sen sitive time resolved immunofluorometric assay (TR-IFMA) using europium as label (detection limit: 0,3 mu g/l). The reliability of the TR-IFM A for the measurement of apolipoprotein B was first studied in serum. Serum and CSF apolipoprotein B concentrations were then determined in subjects free of neurological disorders and in patients with multiple sclerosis. Local intrathecal apolipoprotein B synthesis was calculated . Although the high sensitivity of the TR-IFMA allowed low amounts of apolipoprotein B in CSF to be detected (0.11 +/- 0.06; 0.12 +/- 0.06 m g/l in controls and multiple sclerosis patients, respectively), no apo lipoprotein B could be detected in CSF by electroimmunodiffusion. As s uggested by the blood/CSF apolipoprotein B ratio (about 6000), no apol ipoprotein B synthesis was observed by both using apolipoprotein B ind ex and formula. This indicates its probable serum origin. Moreover, th ere was no difference between controls and multiple sclerosis patients in CSF, serum, blood/CSF, index, and local intrathecal apolipoprotein B synthesis. Finally, these results suggest that the role of apolipop rotein B in lipid transport in the central nervous system may be quest ionable.