Periplaque White Matter Research Articles

Myelin‐associated glycoprotein in multiple sclerosis lesions: A quantitative and qualitative analysis

Myelin-associated glycoprotein (MAG), myelin basic protein (MBP), and proteolipid protein (PLP) were quantitated by immunoassays in nine plaque, inner periplaque, outer periplaque, and normal-appearing white matter regions from brains of five multiple sclerosis patients and compared with the levels found in white matter samples of control subjects matched for age, postmortem time, and brain region. In plaque and inner periplaque regions, all three proteins were substantially reduced due to extensive myelin loss. In outer periplaque regions, MBP and PLP were close to control levels, but MAG was significantly reduced to a mean of 57% of control. All three proteins were close to control levels in the normal-appearing white matter samples. MAG in the various regions was qualitatively examined on Western blots by binding of lectins and by immunostaining with polyclonal and monoclonal antibodies against carbohydrate and protein epitopes of MAG. Densitometric scanning of these blots did not reveal any qualitative differences in the oligosaccharide or polypeptide moieties of MAG between samples from control subjects and those from multiple sclerosis patients. However, a high proportion of the MAG in the multiple sclerosis samples was often in the form of dMAG, a proteolytic derivative of MAG that is formed by a myelin-associated, Ca2+-activated, neutral protease. The preferential loss of MAG at the periphery of multiple sclerosis plaques may be initiated by its proteolytic conversion to dMAG.

Multiple sclerosis: Plaques caused by 2-step demyelination?

Selected studies concerning events at the contour of a progressive plaque are reviewed and an explanation of the subtle changes in periplaque white matter which various investigators have observed on autopsy or biopsy is presented. Recurrent exposure to toxic small molecular weight substances carried by arterial blood and capable of diffusing through the walls of blood vessels cause modification of protein or glycoprotein in the myelin sheath. These then act as allergens (modified native tissue considered as ‘nonself’ tissue by the immune system) which induce antibody formation (termed allo-auto-allergy). Phagocytosis of altered myelin, debris removal and cellular action to maintain homeostasis in the fluid surrounding neurons characterize the premorbid phase of multiple sclerosis. We suggest that the accumulation in the perivascular space of macrophages with large lysosomes digesting myelin debris (visible in electron micrographs) causes bottlenecks in the lymphatic channels serving the extracellular space near nodes of Ranvier. This changes the chemical microclimate and leads to the second step of demyelination and degeneration of the oligodendrocytes, i.e. plaque formation. Reference is made to outstanding problems. Research into the diffusion of small molecular weight substances into the extracellular spaces of white matter would aid in evaluating the hypothesis.

A change in the cerebrosides and sulfatides in a demyelinating nervous system: Development of the methodology and study of multiple sclerosis and Wallerian degeneration

This report describes a new method for the microanalysis of sphingolipids and its application for the characterization of cerebrosides and sulfatides in multiple sclerosis brain and rat sciatic nerves undergoing Wallerian degeneration. Tissue was extracted with isopropanol/hexane (20 : 78), and the total lipids obtained were subjected to benzoylation-desulfation. A portion of this was directly analyzed by silica-column high performance liquid chromatography for the determination of nonhydroxycerebroside, hydroxycerebroside, nonhydroxysulfatide, and hydroxysulfatide. Another portion was fractionated by thin-layer chromatography, and the spots corresponding to the sphingolipid derivatives were eluted. The material from each spot was analyzed by reverse phase high performance liquid chromatography for its homolog composition. With this new procedure the concentrations and homolog compositions of cerebrosides and sulfatides were measured in plaque, periplaque, and normal-appearing white matter from brains of multiple sclerosis patients and Wallerian degenerated rat sciatic nerves distal to the nerve transection. One piece of plaque studied contained only 1.86, 2.76, 0.60, and 0.45 nmol of nonhydroxycerebroside, hydroxycerebroside, nonhydroxysulfatide and hydroxysulfatide/mg of protein, respectively. These concentrations are less than 1% of those found in normal white matter. Periplaques were found to contain concentrations of these sphingolipids between those of plaque and normal white matter. The levels of these sphingolipids in degenerative nerves were 10–20% below normal the third day after the nerve was severed and about 70% below normal after 10 days. The rate of decrease lessened from ten days to 55 days. The homolog compositions of these sphingolipids in both multiple sclerosis brain and degenerating nerves were similar to those in the control. The implications of these findings and the advantages of this new analytical method are discussed.

Analysis of a predominant immunoglobulin population in the cerebrospinal fluid of a multiple sclerosis patient by means of an anti-idiotypic hybridoma antibody.

We have produced hybridoma antibodies directed against immunoglobulins present in the cerebrospinal fluid of a patient with multiple sclerosis (MS). One hybridoma antibody recognized an idiotypic determinant of an immunoglobulin population [an idiotype (Id)] which constituted approximately 1% of the immunoglobulin present in the cerebrospinal fluid. The Id focused in the pH range 8.0-8.4. It was present at roughly 10- to 15-fold higher relative (compared to total immunoglobulin) concentration in cerebrospinal fluid than in serum of the homologous MS patient. The Id could not be detected in three cerebrospinal fluid samples and 28 serum samples of heterologous MS patients or in the serum of 43 optic neuritis patients. The Id persisted in the homologous MS patient at increased concentration over the entire (6 years) observation period. The Id could be shown to react with a Theiler murine encephalomyelitis virus strain WW which was isolated from mice after inoculation with periplaque white matter from brain in a histologically confirmed case of MS.