PRECIPITATION OF MYELIN BASIC PROTEIN BY β-LIPOPROTEIN OF HUMAN SERUM

Myelin basic protein in cerebrospinal fluid and other body fluids

Myelin basic protein (MBP) or a fragment thereof may enter cerebrospinal fluid (CSF) and other body fluids in an etiologically nonspecific fashion to provide information about the status of central nervous system (CNS) myelin damage. MBP immunochemically detected is referred to as MBP-like material (MBPLM). The clinical utility of the assay for MBPLM in CSF is to document the presence, continuation, or resolution of CNS myelin injury. The analysis of CSF for MBPLM is subject to many variables, among which are the antisera and the form of the assay utilized. The dominant epitope of CSF MBPLM is in the decapeptide of 80-89 from the intact MBP molecule of 170 residues. Normally, CSF has no detected MBPLM. Following an acute relapse of MS, MBPLM rises quickly in the range of ng/ml and rapidly declines and disappears. The presence of MBPLM in CSF in chronic and progressive phases of the disease is unusual, but it may sometimes be detected in low levels, depending on the assay used for detection. The level of CSF MBPLM is related to both the mass of CNS myelin damage and how recently it occurred. The level of CSF MBPLM rarely is elevated in optic neuritis. The level of CSF MBPLM is unrelated to CSF protein level, level of IgG, presence of oligoclonal bands or pleocytosis. CSF MBPLM has the potential of serving as a marker of therapeutic effectiveness in MS and does have predictive value for response to glucocorticoids given for worsening of disease. The detection of MBPLM in body fluids other than CSF would be of great value because of the resulting improved feasibility for objectively monitoring the natural history of MS and response to therapy. Studies on blood have yet to produce a valid assay of MBPLM. Urinary MBPLM, though different in its features from that in CSF, may provide a correlate, not with acute demyelination in MS as is the case for CSF, but with progression of disease.

Molecular features of immunoreactive myelin basic protein in cerebrospinal fluid of persons with multiple slcerosis

The molecular weight of the myelin basic protein (BP)-like material appearing in cerebrospinal fluid (CSF) of 2 persons with active-phase multiple sclerosis (MS) and 3 with recent cerebral infarctions was determined by gel filtration chromatography under acidic conditions. Column fractions were examined by radioimmunoassay for BP peptide 43-88 antigen as well as for binding activity to BP. Material cross-reactive with BP peptide 43-88 eluted over a wide spectrum of molecular weights. Greater representation of lower molecular weight species occurred in MS. Fractionated CSF from 2 patients with MS and 2 with cerebral infarction contained binding activity, presumably antibody, to BP which was greater than that in unfractionated CSF. Binding to BP was also examined in unfractionated CSF from 70 persons, including 16 with MS and 36 with other neurological diseases. Although CSF from MS patients showed higher binding, the presence of BP binding activity was not specific for MS. Our findings suggest that the antigen cross-reacting with BP and its fragments in CSF appears in a spectrum of molecular weight species, with lower forms predominating in MS. The detection of binding activity to BP as well as its enhancement by treatment at low pH suggest that the BP-like antigen in CSF may exist in free as well as in complexed forms.

Studies on the inactivation of encephalitogenic myelin basic protein by serum

This study confirms previous reports that myelin basic protein loses its encephalitogenic activity when incubated in normal serum at 37 degrees C. The mechanisms for this was studied. 125I-labelled human myelin basic protein was rapidly degraded by normal guinea pig serum to low molecular weight products as shown by polyacrylamide gel electrophoresis. An intermediate product of molecular weight about 6000 daltons was seen. Plasma had a much lower degradative activity than serum; the half life of myelin basic protein was 3.8 hours in plasma compared with 12 minutes in serum. Serum degraded myelin basic protein was no longer capable of suppressing experimental allergic encephalomyelitis in the guinea pig nor of eliciting delayed-type hypersensitivity in guinea pigs sensitized to myelin basic protein.