Demyelinating polyneuropathy associated with monoclonal IgM-paraproteinaemia. Histological, ultrastructural and immunocytochemical studies

Heterogeneous spectrum of neuropathies in Waldenström's macroglobulinemia: a diagnostic strategy to optimize their management

Neuropathy in Waldenström's macroglobulinemia (WM) is very heterogeneous. We retrospectively studied 40 patients with WM and neuropathy to analyze the different presentations and mechanisms encountered and to propose a diagnostic strategy. Twenty-five patients (62.5%) had axonal neuropathy, related to the following mechanisms: amyloid neuropathy (n = 5), cryoglobulinemic neuropathy (n = 5), neuropathy associated with tumoral infiltration (n = 2), vasculitic neuropathy (n = 2), a clinical motor neuropathy possibly of dysimmune origin (n = 6), or an unclassified mechanism (n = 5). A demyelinating pattern was observed in 15 patients, 10 having anti-myelin-associated glycoprotein (anti-MAG) antibodies and 5 having neuropathy related to chronic inflammatory demyelinating polyradiculoneuropathy. On the basis of these results, we propose a diagnostic strategy combining: (1) an EMG to distinguish between a demyelinating and an axonal pattern; (2) measurement of anti-MAG and anti-ganglioside antibodies; (3) screening for "red flag" features to orientate further investigations. This strategy may help clinicians to identify the mechanism of neuropathy in order to adapt the therapeutic strategy.

Long-term clinical and neurophysiological follow-up of patients with peripheral, neuropathy associated with benign monoclonal gammopathy

The incidence of hematological malignancy in patients with monoclonal gammopathy of undetermined significance (MGUS) has been assessed as 17% to 25%. To ascertain whether this is true of neuropathy associated with MGUS, a long-term (5-42 years) retrospective clinical and neurophysiological follow-up was conducted in 50 cases (immunoglobulin M [IgM], n = 38; IgG, n = 11; IgA, n = 1). Only three patients developed hematological malignancy. Of 25 survivors with IgM paraproteinemia, 7 had myelin-associated glycoprotein antibodies with typical clinical features. Evoked distal muscle amplitudes were significantly smaller than for the other paraprotein classes. Preferential distal demyelination manifested by relative prolongation of distal motor latency was not apparent in the cases of long duration. Two patients with IgM antidisialosyl antibodies and cold agglutinating activity had a large fiber neuropathy with intermittent oculofacial involvement. Both responded to intravenous immunoglobulin. Findings in the remaining patients were varied. Recognition of IgM subgroups is important both for prognosis and possible response to treatment.

Myelin modifications in 8 cases of peripheral neuropathy with Waldenström's macroglobulinemia and anti-MAG activity

Characteristic myelin modifications in patients with IgM monoclonal gammopathy and anti-MAG activity have mainly been studied in cases of undetermined significance, but also exist in cases with indolent Waldenström's macroglobulinemia, i.e., when lymphoplasmocytic infiltration in bone marrow is 15% or more, without any visceral involvement. Since 1983, the authors have examined nerve biopsies from 8 cases with Waldenström's macroglobulinelia by direct immunofluorescence examination on frozen sections and ultrastructural examination. At direct immunofluorescence, fixation of anti-IgM serum on myelinated fibers was present in 7 cases. At ultrastructural examination, a widening of some myelin lamellae at the periphery of a few fibers was visible in 8 cases. A few fibers with hypermyelination were present in 5 cases. In 2 of these 5 cases widening of some myelin lamellae was present in numerous fibers, 88% in one of them. Frequently, there was a major widening of some myelin lamellae with dilated lamellae present in the inner part of the myelin sheath. Certain lamellae were more dilated, up to 50 nm. Occasionally, enlarged lamellae were not compacted with each other. The authors also examined nerve biopsies from 36 patients with IgM monoclonal gammopathy of undetermined significance and anti-MAG activity, but found only one case with major widening of some myelin lamellae. Five other cases with major widening of some myelin lamellae, 4 Waldenström's macroglobulinemia and 1 IgM monoclonal gammopathy of undetermined significance, have been reported. Given that demyelinating neuropathies are far more numerous in cases with IgM monoclonal gammopathy of undetermined significance, it is likely that cases of indolent Waldenström's macroglobulinemia are prone to develop major myelin modifications, possibly due to another mechanism, added to the classic anti-MAG activity.

Morphological changes at paranodes in IgM paraproteinaemic neuropathy

The paranode is one of a number of sites of a specific myelin sheath abnormality found in cases of IgM paraproteinaemic neuropathy. The gammopathy may be malignant or, more frequently, benign, and is often associated with a predominantly demyelinating neuropathy. The circulating paraprotein IgM antibody, usually with kappa light chains, was found in many cases to recognise an antigenic determinant in myelin, identified as myelin-associated glycoprotein (MAG). Other glycoconjugates expressed by Schwann cells may also be recognised by the antibody. MAG is localized to regions of the myelin sheath in which the membranes are uncompacted. The paranode is one such region, and there is evidence that IgM is deposited specifically on the membranes of the terminal loops of the myelin sheath in addition to other MAG-associated regions of the sheath. In many cases the presence of the paraprotein appears not to otherwise affect paranodal organization; in a few it is associated with changes to the termination of the loops on the axolemma and to the associated Schwann cell cytoplasm. These findings do not provide unambiguous evidence that binding of anti-MAG IgM antibodies at the paranode is a direct cause of demyelination. Whilst localization of the paraprotein closely matches that of MAG, proof is still lacking that the relevant antigen is MAG itself.

Subcellular Distribution of Sulfated Glucuronyl Glycolipids in Human Peripheral Motor and Sensory Nerves

Sulfated glucuronyl glycolipids (SGGL) have been implicated as important target antigens in patients with demyelinating polyneuropathy and IgM paraproteinemia. Sulfated glucuronyl paragloboside (SGPG), a major species of SGGL, was identified in the subcellular fractions of human peripheral motor and sensory nerves using a simple and quantitative method. SGPG was found to be concentrated in the myelin-enriched fractions of both motor and sensory nerves (1.3 +/- 0.3 and 1.5 +/- 0.4 &mgr;g/mg protein, respectively), whereas its concentration was 0.9 +/- 0.2 and 1.8 +/- 0.6 &mgr;g/mg protein in the axolemma-enriched fractions of motor and sensory nerves, respectively. Our finding that SGPG is more abundant in the human sensory nerve axolemma-enriched fraction may account for the clinical and pathological observations that the lesions are more heavily concentrated in the sensory nerve than in other parts of the nerve tissues in this disorder. Copyright 1994 S. Karger AG, Basel

Susceptibility to demyelinating polyneuropathy in plasma cell dyscrasia may be influenced by amino acid position 9 of the HLA-DR beta chain

Fifty-five patients with plasma cell dyscrasias were investigated by genomic typing for HLA-DR and -DQ genes by restriction fragment length polymorphism, neurophysiology and for presence of anti-myelin-associated glycoprotein (MAG) antibodies. In 26 patients, a polyneuropathy (PN) of demyelinating type was established. Among these individuals, an association was found with the presence of a tryptophan amino acid residue at position 9 of the DR beta chain (P < 0.01). This position is part of the first hypervariable region of the DR beta chain, and may be of importance in determining preferential peptide-binding capacity of the HLA-DR molecule. The presence of anti-MAG antibodies in 15 out of 17 patients with an IgM M-component and demyelinating PN (14 of these 15 individuals carrying a tryptophan at position 9) supports the pathogenic role of an autoimmune response against MAG. The finding of an HLA class II association may indicate a pathogenic role of T cell immunity in this condition.

Immunoelectron microscopic localization of monoclonal IgM antibodies in gammopathy associated with peripheral demyelinative neuropathy

A sural nerve biopsy from a patient with benign monoclonal IgM kappa gammopathy and sensory-motor demyelinative neuropathy, revealed marked loss of myelinated fibers and focal axonal degeneration as well as widespread demyelination and remyelination with onion-skin formation. Almost all myelinated fibers displayed characteristic widening of the myelin lamellae as well as excessive thickness and/or exuberant outfoldings of myelin, reminiscent of that seen in tomaculous neuropathy. Many endoneurial capillaries were lined by fenestrated endothelium, indicating breakdown of a normal blood-nerve barrier. The endoneurium contained large amounts of extracellular proteinaceous material. Immunofluorescence and immunoelectron microscopy performed on the nerve of the patient, demonstrated selective deposition of IgM kappa gammaglobulin, exclusively in the areas of splittings of the myelin lamellae. Schwann cells contained cytoplasmic myelin debris labelled with IgM kappa only. In the indirect immunofluorescence and immunoelectron microscopy, serum of the patient reacted with the whole thickness of compact peripheral myelin of a normal human nerve. There was no immunoreactivity with the central myelin, Schwannoma cells, glial cells, axons or neurons. Demonstration of the selective presence of monoclonal IgM in widened lamellae of myelinated fibers, as well as bound to the internalized myelin debris in Schwann cells and macrophages, indicates a pathogenetic role of monoclonal paraprotein in myelin injury. Demyelination is promoted by development of endothelial fenestrations in the endoneurial capillaries and breakdown of the blood-nerve barrier.

Immunochemical and clinical effects of immunosuppressive treatment in monoclonal IgM neuropathy

A pathogenic role of the M protein in monoclonal IgM neuropathy has been suggested. This is based among other things on a close relation between immunosuppressive treatment, lowered concentration of M protein, and clinical effect. We studied five patients with monoclonal IgM and antibodies to peripheral nerve myelin. The immunosuppressive treatment was beneficial in three of the patients. In three patients there was a relationship between antibody concentration and clinical effect (in one there was no change in antibody concentrations and correspondingly no change in clinical status, and in two patients clinical improvement corresponded to decreased antibody concentrations). In two patients, however, there was no clear correlation, since one patient improved despite increasing antibody concentrations and one patient did not improve despite a lowered antibody concentration. It is therefore possible that other mechanisms may contribute to the effect of treatment.

Sensorimotor polyneuropathy and monoclonal IgM: a review of clinical and immunological features

Main clinical and biological features of peripheral neuropathies associated with monoclonal IgM are reviewed. Special emphasis is given to the structure of these monoclonal auto-antibodies which points to an antigen (or some other kind of selective pressure) driven process.

The clinical spectrum of peripheral neuropathies associated with benign monoclonal IgM, IgG and IgA paraproteinaemia. Comparative clinical, immunological and nerve biopsy findings

Observations have been made on a consecutive series of 62 patients with peripheral neuropathy associated with benign monoclonal paraproteinaemia. The paraprotein class was IgM in 46 cases, IgG in 11 and IgA in 5. Although showing variations between patients, the clinical picture was similar for those with either IgM or IgG paraproteins, usually consisting of a late-onset, slowly progressive, distal sensorimotor demyelinating polyneuropathy, often with tremor and ataxia as prominent features. Tremor was slightly more common in patients with IgM paraproteins, in whom there was a male preponderance. The patients with both paraprotein classes were indistinguishable clinically and electrophysiologically from chronic idiopathic demyelinating polyneuropathy. In the 5 patients with an IgA paraprotein, there was a distal sensorimotor neuropathy in 4 which was demyelinating in 1. In 1 there was proximal demyelinating motor neuropathy. Immunoglobulin deposition on myelin was observed only in the patients with IgM paraproteinaemia, more commonly with a kappa light chain. No deposition of immunoglobulin in the endoneurium was seen. IgM deposits on the perineurium are a feature of normal nerve and were present in all cases. Widely spaced myelin was confined to cases with IgM paraproteins in which immunoglobulin deposition was detected on myelin. The response to treatment could not be assessed systematically but, in general, the patients with IgG and IgA paraproteins responded more satisfactorily (to corticosteroids, cytotoxic drugs, or plasma exchange) than did those with an IgM paraprotein.

Axonal neuropathy in a patient with monoclonal IgM kappa reactive with Schmidt-Lantermann incisures

We report a patient with a progressive, predominantly sensory neuropathy and a IgM kappa M-protein that binds to Schmidt-Lantermann incisures. A sural nerve biopsy showed primary axonal damage and IgM deposits at Schmidt-Lantermann incisures were seen by direct immunoperoxidase. Serum from the patient injected into rat sciatic nerve reacts with the incisures as with those in the patient's nerve. The IgM kappa M-protein reacts with chondroitin sulfate C and binds to a broad nerve protein band with a mobility of between 170 and 118 kDa. Peripheral neuropathy may be related to the M-protein, which had immunocytochemical reactivity not previously described for patients with polyneuropathy and IgM monoclonal gammopathy.

Polyneuropathy associated with IgA monoclonal gammopathy: a hypothesis of its pathogenesis

We describe three patients with chronic progressive polyneuropathy associated with IgA monoclonal gammopathy. Two patients had a prominent sensory neuropathy and one had a prominent motor neuropathy. Sural nerve biopsies showed axonal degeneration in all cases. In immunocytochemical studies patients' IgG immunostained axons. By Western immunoblot a band of IgG reactivity with an axonal protein of 66 kDa was found. No band of IgA and IgM were found. We suggest the possibility that the IgA monoclonal protein may act as a stimulating factor of preexisting B cell clones eliciting an immune reaction against nerve antigens.

Morphological changes in IgM paraproteinaemic neuropathy

Sural nerve biopsies were examined from two patients with neuropathy associated with IgM kappa [anti-myelin-associated glycoprotein (MAG)] paraproteinaemia. Both nerves had a moderate loss of myelinated fibres. The pathology in one was of a chronic primary demyelinating type, in the other it was associated with axonal atrophy. Widened myelin (WM) was seen in both nerves affecting over 80% and 50% of myelinated fibres, respectively. The WM was associated with deposition of material which sometimes appeared granular but could also display a highly organised pattern, an appearance not previously described in these neuropathies. Granular material was also identified at the external surface of the Schwann cells of myelinated, but not of unmyelinated, fibres. WM was seen not only at the outer lamellae (a commonly observed site) but also at terminal myelin loops at the paranode, at Schmidt Lanterman incisures and at the inner and outer mesaxon. Material was also seen on the inner (adaxonal) Schwann cell surface. These are all sites associated with the presence of MAG. Other pathological features are described, including evidence of impairment of remyelination, abnormal Schwann cell/axon specialisations and the presence of tomaculous bodies. The implications of these findings are discussed.

Anti-myelin-associated glycoprotein IgM antibody titers in neuropathy associated with macroglobulinemia

Twenty-seven patients with neuropathy and IgM monoclonal gammopathy were tested for antigen specificity of the M-protein and for anti-myelin-associated glycoprotein (MAG) IgM levels by immunoblot. In 16 patients (59.2%) the M-protein reacted with MAG and with cross-reactive glycoconjugates. Anti-MAG IgM titers in these patients ranged between 1:12,800 and 1:100,000. A fainter IgM reactivity with MAG and related glycoconjugates was detected in 3 additional patients with neuropathy, but also in 8 of 24 patients with IgM M-protein without neuropathy (33.3%). This reactivity was not due to the M-protein and corresponded to antibody titers of 1:400 or less in all but 1 patient with a titer of 1:3,200. Low titers of anti-MAG IgM (1:200 or less) were also detected in 17 of 101 control patients without IgM M-proteins (16.8%), while 1 patient with neuropathy of unknown cause had anti-MAG IgMK titers of 1:25,600. In 1 patient with neuropathy and IgM M-protein that was not anti-MAG, the M-protein bound to other antigens in nerve, while in 6, other possible causes or mechanisms for the neuropathy were found. In this study, high titers of anti-MAG IgM antibodies were always associated with neuropathy. The presence of low levels of anti-MAG IgM in a significant proportion of controls suggests that monoclonal expansion of naturally occurring B-cell clones secreting anti-MAG IgM may be responsible for the high incidence of this antigen specificity of the M-protein.

Microangiopathy of endoneurial vessels in hypoxemic chronic obstructive pulmonary disease (COPD). A quantitative ultrastructural study

A peripheral neuropathy has been reported in patients with chronic respiratory insufficiency due to chronic obstructive pulmonary disease (COPD). It is mainly characterized by axonal degeneration, secondary demyelination and abnormal endoneurial vessels. The pathogenesis of these lesions remains obscure. To investigate whether relationships exist between neuritic and vascular lesions, a qualitative and quantitative ultrastructural study was performed on nerve biopsies in 13 patients with chronic respiratory insufficiency due to COPD, and in 9 normal controls without pulmonary lesions. A computer-assisted multiple regression analysis taking into account clinical, electrophysiological, biological and morphometric parameters was performed. Statistically significant differences in the endoneurial structure of microvessels were: (1) thickening of the basement membrane; (2) narrowing of the lumen; (3) mural pericytic debris deposits, occurring in the COPD group. In the latter, hypercapnia correlated positively with nerve fibers lesions (P = 0.03) and endothelial area (P = 0.03). No correlations were found between age and other parameters. These findings highlight the fact that the microangiopathy in peripheral nerves in patients with COPD may be diffuse and essentially due to hypoxia and reduction in blood flow, as in diabetic neuropathy.

Demyelination induced by intraneural injection of human antimyelin-associated glycoprotein antibodies

IgM monoclonal antibodies present in the sera from some patients with peripheral neuropathy react with an antigenic carbohydrate determinant that is present on the myelin-associated glycoprotein (MAG) and other peripheral nerve glycoproteins and glycolipids. It is generally believed that the neuropathy in these patients may be caused by antibody- mediated nerve damage. Intraneural injection of serum from patients with this disease produced an extensive inflammatory, macrophage-mediated demyelination of feline peripheral nerve. This only occurred with very fresh sera which had been supplemented with additional complement. Injection of sera from normal subjects failed to produce any demyelination. These results are in accordance with a recent study by Hays et al. and contradict earlier negative reports of similar studies. It is important to note that the pathology observed in these experimental studies bears little resemblance to that seen in the human neuropathy, and caution must therefore be exercised when interpreting this data in relation to the pathogenic mechanisms that might operate in the human disease.

Treatment of patients with neuropathy and anti-MAG IgM M-proteins

Five patients with neuropathy and IgM M-proteins that reacted with myelin-associated glycoprotein (MAG) were treated for 10 to 20 months with cytostatic agents. In 2 patients, a decrease in serum M-protein and in anti-MAG IgM levels coincided with a progressive improvement of neuropathy. No clinical improvement and no decrease of anti-MAG IgM were observed in the other patients. The close relationship between the decrease of anti-MAG M-proteins and clinical improvement in these patients supports the pathogenetic role of the M-protein in the neuropathy.

Visual evoked potentials in patients with neuropathy and macroglobulinemia

Visual evoked potentials were studied in 11 patients with neuropathy and macroglobulinemia. The P100 latency was increased bilaterally in 5 of the 6 patients whose IgM M-proteins reacted with myelin-associated glycoprotein (MAG) and in 1 of the other patients. In patients whose M-protein bound to MAG, abnormal visual evoked potentials correlated with the presence of the M-protein in the cerebrospinal fluid. Subclinical involvement of the central nervous system is frequent in patients with neuropathy and anti-MAG M-proteins and may be due to the binding of M-proteins to central nervous system myelin.

Demyelinating optic neuropathy with Miller-Fisher syndrome. The case for overlap syndromes with central and peripheral demyelination

The syndrome of ataxia, areflexia and ophthalmoplegia, or Miller-Fisher syndrome, has been considered to be a variant of Guillain-Barré syndrome with pathology restricted to the peripheral nervous system. A patient with Miller-Fisher syndrome and bilateral demyelinating optic neuropathy suggesting associated central nervous system pathology is presented. Clinical and experimental evidence regarding the association of central and peripheral nervous system demyelination is reviewed.

Humoral factors in peripheral nerve disease

Humoral factors including soluble substances transported by the blood stream and factors released at a target tissue may play a role in diseases of the peripheral nervous system. Various criteria have to be met in order to accept humoral factors as potential pathogens. In this review these general criteria are discussed, including the evidence provided by plasma exchange therapy, demonstration of circulating or deposited autoantibodies and immune complexes, identification of antigenic molecules, animal model diseases, passive transfer experiments, and the demonstration of circulating factors not directed against specific targets. In acute, chronic, and chronic relapsing inflammatory polyneuropathies, and in the polyneuropathy associated with monoclonal gammopathy, humoral factors have been identified, but their exact pathogenic role is not fully understood. In the Lambert-Eaton myasthenic syndrome, a disorder of the motor nerve terminal, pathogenic IgG-antibodies have been demonstrated by passive transfer experiments. In the experimental animal model disorders, the acute and chronic variants of experimental allergic neuritis, humoral factors including antibodies to myelin basic proteins and galactocerebroside and nonspecific humoral factors may all contribute to the ultimate peripheral nerve damage, but their relative importance in relation to cell-mediated immune reactions is not yet clear.

Polyneuropathy in paraproteinaemia

Paraproteinaemias are frequently associated with peripheral neuropathies. "Benign" paraproteinaemia, myeloma and Waldenströms macroglobulinaemia may present clinically as polyneuropathy. Therefore immunoelectrophoresis is strongly recommended in the routine diagnosis of polyneuropathies of unknown origin. Peripheral neuropathies associated with paraproteinaemia are clinically, electrophysiologically, pathologically and probably also pathogenetically heterogeneous. There are subgroups such as demyelinating neuropathy associated with IgM paraproteinaemia, which show quite distinctive features. This survey describes the different types of paraproteinaemia and their associated peripheral neuropathies. The incidence, pathogenesis and therapy of peripheral neuropathy associated with monoclonal gammopathies are discussed.

Immunohistochemical recognition of human nerve sheath tumors by anti-Leu 7 (HNK-1) monoclonal antibody

Using relatively high dilutions of anti-Leu 7 monoclonal antibody and a four-step peroxidase-antiperoxidase (PAP) reaction in paraffin-embedded tissues, we tested the affinity of this antibody to the cells of 47 human nerve sheath tumors and 22 other tumors in which the differential diagnosis with nerve sheath neoplasms is known to arise. Of all the nerve sheath tumors studied 68%, including 80% of the schwannomas, contained anti-Leu 7-positive cells. All 22 non-schwannian neoplasms were entirely negative. Specimens of eight experimental malignant rat schwannomas were also negative for anti-Leu 7 antibody. Our findings suggest that anti-Leu 7 monoclonal antibody is a promising marker that may facilitate the differential diagnosis between human Schwann cell and non-Schwann cell neoplasms.

Immunocytochemical studies of serum proteins and immunoglobulins in human sural nerve biopsies

Post-embedding immunocytochemical studies on immunoglobulins (Ig) and other serum proteins were carried out on 38 human sural nerve biopsies using the PAP method. In addition to toxic, hereditary, metabolic, dysproteinemic, and vasculitic-neuritic neuropathies, morphologically normal sural nerves were included as controls. The intensity of the immunocytochemical reactions was strong for proteins, such as IgG, the light chains of Igs, and albumin, but weak or absent for others like complement component C3, IgA, ceruloplasmin, and alpha-1-antitrypsin (AAT) in normal nerve biopsies and in all pathologic groups. IgG, the light chains of immunoglobulins, and albumin could readily be detected in perineurium, endoneurial interstitium, and blood vessel walls. IgM, C3, and beta-lipoprotein (BLP) were largely confined to the walls of blood vessels and perineurium, thus indicating that they do not penetrate the blood nerve barrier. Only in a few cases, in vasculitic-neuritic and dysproteinemic neuropathies, staining of the endoneurial interstitium for IgM and C3 was observed. Increased staining for the corresponding heavy or light chains was not detected in the endoneurium in any of the neuropathies associated with gammopathy. The results stress that PAP immunocytochemistry is suitable for studying the blood-nerve barrier (BNB) and provides new aspects to the concept of the BNB with respect to the steady state of serum proteins between endoneurial and vascular spaces. It is suggested that, in addition to serum concentration and molecular weight of serum proteins, the permeability of the BNB is influenced by other yet undefined factors.

Immunocytochemical studies in canine neuroectodermal brain tumors

Seventy-four canine neuroectodermal tumors were examined immunocytochemically for the presence of glial fibrillary acidic protein (GFAP). Eleven oligodendrogliomas were examined for the presence of myelin basic protein (MBP) and myelin-associated glycoprotein (MAG). Twenty-three tumors, including ten astrocytomas, one ependymoma, two glioblastomas, one case of gliomatosis, and nine poorly differentiated gliomas were positive for GFAP. Two astrocytomas, eleven oligodendrogliomas, eight ependymomas, four choroid plexus papillomas, two medulloblastomas, one glioblastoma, nine poorly differentiated gliomas, six cases of gliomatosis, and three unclassified tumors were GFAP-negative. In six tumors (including four that were classified as astrocytoma) GFAP staining was equivocal. All oligodendrogliomas were MBP-negative but three expressed MAG. It was concluded that many canine gliomas are not only morphologically but also immunocytochemically similar to human gliomas, but that a larger proportion of canine neuroectodermal growths are undifferentiated tumors.

Myelin-associated glycoprotein is produced before myelin basic protein in cultured oligodendrocytes

Mixed glial cell cultures from neonatal dog cerebellum were harvested daily between 3 and 21 days after seeding and studied with immunocytochemical techniques for the demonstration of myelin-associated glycoprotein (MAG) and myelin basic protein (MBP). Both MAG and MBP were detected in the cultures and by means of double labelling techniques shown to be produced by the same cells. MAG+ cells occurred earlier and were always more numerous than MBP+ cells. These results suggest that the oligodendrocyte in vitro expresses MAG before MBP. The findings are discussed in respect to oligodendroglial differentiation and myelination in vivo.

Polyneuropathy in Waldenström's macroglobulinaemia: reduction of endoneurial IgM-deposits after treatment with chlorambucil and plasmapheresis

A case of progressive polyneuropathy associated with Waldenström's macroglobulinaemia is reported. A monoclonal IgM-lambda gradient was detected in the serum and cerebro-spinal fluid. By electro-immunoblot analysis antibodies against myelin-associated glycoprotein were found in the serum and cerebro-spinal fluid. The motor and sensory conduction velocities of several peripheral nerves were markedly decreased, and examination of visual evoked potentials (VEPs) revealed pathological latencies. Sural nerve biopsies before and after treatment with chlorambucil and plasmapheresis showed nerve fibre loss and demyelination. In the pre-treatment biopsy, heavy accumulations of filamentous material were found which stained positively for IgM by immuno-cytochemistry. Such accumulations had disappeared in a biopsy performed after treatment. The morphological findings were correlated with an improvement of clinical and electro-physiological findings.