Microheterogeneity of anti-myelin-associated glycoprotein antibodies

Antibodies to the myelin-associated glycoprotein (MAG) are implicated in the pathogenesis of an acquired demyelinating polyneuropathy. We studied IgM affinity to MAG in 18 patients with anti-MAG antibodies. Binding of sera was tested for anti-MAG immunoreactivity in central nervous system (CNS) by ELISA and in CNS and peripheral nervous system (PNS) by Western blot analysis. Furthermore, immunohistochemical characterization of IgM binding on sural nerve tissue was investigated using the indirect peroxidase method. Western blot analysis revealed that all sera detected MAG in central myelin, but only eight in peripheral myelin. Anti-MAG-IgM-ELISA-titers correlated significantly (p<0.0001) with PNS-Western blot results. By indirect immunoperoxidase immunohistochemistry, 12 sera stained myelin sheaths, while 6 sera showed no staining. These results demonstrate considerable variations in antibody binding strength to MAG between PNS myelin and CNS myelin. The relevance of these differences for the pathogenesis of the neuropathy and clinical impairment remains to be demonstrated.     

Analysis of the feline immune response to human myelin-associated glycoprotein

Elucidation of the pathogenesis of demyelinating peripheral neuropathy associated with myelin-associated glycoprotein (MAG) binding IgM paraproteins requires an in vivo animal model of the syndrome. Multiple immunizations of cats with MAG in Freund's adjuvant did not produce an antibody response but four immunizations with MAG-iscom (Morein, B. et al. (1984) Nature, 308: 457-460) did induce IgM antibodies which bound to human MAG and cat peripheral nerve myelin. Despite the presence of antibody for a 13-month period, no neuropathy developed. At necropsy, the peripheral nerves were ultrastructurally normal and no antibody was detectable in the endoneurium. A competitive ELISA indicated that the cat and human IgM antibodies recognized different epitopes.     

Characterization of HNK-1 bearing glycoproteins in human peripheral nerve myelin.

The HNK-1 carbohydrate epitope, which is shared by several members of the immunoglobulin gene super-family, is also the target epitope for IgM anti-MAG autoantibodies in patients with demyelinating neuropathy. By Western blot analysis, there are 7 HNK-1 immunoreactive glycoproteins in human peripheral nerve myelin, two of which have previously been identified as the myelin associated glycoprotein (MAG) and the P0 glycoprotein. In this study, the remaining HNK-1 bearing glycoprotein bands were characterized by immunoblot and NH2-terminal sequence analysis, and were all identified as degradation products or aggregates of the Po glycoprotein. MAG and P0 are therefore the only HNK-1 bearing glycoproteins in human peripheral nerve myelin.     

Anti-MAG IgM penetration into myelinated fibers correlates with the extent of myelin widening.

The purpose of this study was to evaluate the relationship between immunoglobulin M (IgM) antibodies penetration into myelinated peripheral nerve fibers and the widening of the peripheral myelin sheaths in anti-myelin-associated glycoprotein (anti-MAG) demyelinating IgM monoclonal polyneuropathy. Demyelinating polyneuropathy with monoclonal IgM is often associated with anti-MAG autoantibodies, which are thought to initiate the disease with IgM deposits usually present on the myelin sheaths. We analyzed nerve biopsies from 12 patients with an anti-MAG demyelinating neuropathy by confocal and electron microscopy. The total number of nerve fibers and the proportion of IgM-associated fibers were quantified after immunohistochemical staining. The affinities of IgM were examined by analyzing the binding pattern of serum IgM on normal peripheral nerve sections. Ultrastructural examinations of the biopsies showed a good correlation between in situ widened myelin sheaths and the IgM penetration level into myelinated fibers. The terminal complement complex appears not be involved in the penetration of IgM into the myelinated fibers. Our findings suggest a causative role of the IgM anti-MAG antibodies in the ultrastructural modifications of the myelin sheaths. The basement membrane and myelin components appear to be the major targets of the IgM monoclonal antibodies. However, the pathogenic mechanism whereby IgM antibodies reach their targets and induce nerve damage are still unclear.     

Anti‐ganglioside antibodies in Guillain–Barré syndrome and chronic inflammatory demyelinating polyneuropathy in Chinese patients

Introduction: In this study we investigated the relationships between anti‐ganglioside antibodies and Guillain–Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP). Methods: Samples from 48 Chinese patients diagnosed with GBS and 18 patients diagnosed with CIDP were retrospectively reviewed. Results: In the GBS patients, 62.5% were classified as having acute inflammatory demyelinating polyneuropathy (AIDP), 27.1% were found to have acute motor axonal neuropathy (AMAN), and 10.4% were unclassified. Serum IgG anti‐ganglioside antibodies were detected in 46.2% of the AMAN patients and in 6.7% of the AIDP patients (P < 0.05); 5.6% of the 18 CIDP patients were IgG antibody positive, and 27.8% were IgM antibody positive. Facial palsy and sensory impairment were significantly associated with IgM antibodies. Conclusions: These results suggest that IgG anti‐GM1 antibodies are associated with AMAN, but not with AIDP, and that IgM antibodies against GM1, GM2, and GM3 are associated with facial nerve palsy. Muscle Nerve 55 : 470–475, 2017     

Widening of myelin lamellae in polyneuropathy with immunoglobulin-M monoclonal gammopathy,without activity against myelin-associated glycoprotein,responsive to treatment

We report the case of a patient with a very severe predominantly demyelinating sensorimotor polyneuropathy (with axonal loss) that had developed over several months, along with an immunoglobulin-M monoclonal gammopathy without anti-myelin associated glycoprotein antibodies (or other antibodies against myelin). Widening of myelin lamellae were frequently observed by electron microscopic examination of a nerve biopsy: immunoglobulin-M targeting an unknown myelin antigen appears to be responsible for the nerve lesions similar to those observed in anti-myelin associated glycoprotein polyneuropathy. Usually, if in anti-myelin associated glycoprotein neuropathy the response to immunotherapies is not optimal, in this case the combination of plasma exchanges and rituximab was effective, suggesting an autoimmune origin.     

Anti-myelin-associated glycoprotein neuropathy

PURPOSE OF REVIEW: The anti-myelin-associated glycoprotein (MAG) neuropathy is an antibody-mediated demyelinating neuropathy. The clinical picture is characterized by a distal and symmetric, mostly sensory neuropathy. Monoclonal immunoglobulin M anti-MAG antibodies are uniquely found in this condition and are believed to be pathogenic. This review focuses on recent progress in understanding the mechanisms of this neuropathy and discusses new therapeutic advances. RECENT FINDINGS: Different electrophysiological parameters have been demonstrated to distinguish the anti-MAG-associated polyneuropathy from chronic inflammatory demyelinating polyneuropathy. The electrophysiological findings generally indicate a predominantly demyelinating neuropathy with a distal accentuation of conduction slowing. Analyses of pathology in nerve tissue from anti-MAG patients using classical nerve biopsy or skin biopsy tissue demonstrated immunoglobulin M deposits at the site of MAG localization, demyelination and axonal degeneration. MAG is a Schwann cell-based glycoprotein and has been implicated as a mediator of an outside-in signaling cascade influencing the cytoskeletal integrity of axons. SUMMARY: Therapy in patients with anti-MAG neuropathy is directed at reducing the antibody concentration, blocking the effector mechanisms and depleting the monoclonal B cells. The recent availability of rituximab, a monoclonal antibody suppressing B-cell clones, which is not myelosuppressive and does not cause secondary malignancies, allows for early targeted intervention.     

Neuropathy and paraproteins: review of a complex association

Coexistence of neuropathy and monoclonal gammopathy represents a common but complex problem in clinical practice. This association is here reviewed considering latest available literature. The association is not infrequent, and various possible syndromes need to be distinguished. However, coincidental co‐occurrence also needs to be recognized. The monoclonal gammopathy may be a ‘monoclonal gammopathy of uncertain significance’ (MGUS) or occur in a context of malignancy such as multiple myeloma or Waldenström’s macroglobulinaemia. IgM paraproteins can bind to myelin‐associated glycoprotein (MAG) in peripheral nerve. In this case, the paraprotein is directly linked to the neuropathy, causing a specific phenotype. One randomized controlled trial of this (‘Anti‐MAG’) neuropathy showed possible moderate effect of rituximab on disability. Results of another trial are awaited. IgM/G/A paraproteins can be associated with a polyneuropathy indistinguishable from chronic inflammatory demyelinating polyneuropathy. Axonal neuropathies may coexist with IgM/G/A MGUS. There is insufficient evidence about causality or effective treatment in such cases. Pain/dysautonomia with an axonal neuropathy and serum paraprotein raises the possibility of amyloidosis. Specific haematological treatment is required for malignant disorders, although caution is required with neurotoxic agents. Polyneuropathy, organomegaly, endocrinopathy, M‐protein, skin changes syndrome and chronic ataxic neuropathy with ophthalmoplegia, M‐protein, cold agglutinins and disialosyl antibodies represent rare separate entities for which evidence‐based treatment options are still lacking. The association of monoclonal gammopathy and neuropathy requires the appropriate neurological/haematological investigations for a precise diagnosis. Causality is only established in few cases. Adequate management ideally requires joint neurological/haematological input for diagnosis, monitoring and treatment.     

Acute idiopathic demyelinating polyneuropathy: passive transfer to mice by immunoglobulin

Systemic administration of acute idiopathic demyelinating polyneuropathy (AIDP) immunoglobulins to mice for two weeks resulted in reduced sural nerve action potential amplitudes and reduced (rotarod) motor performance. Electron microscopic examination of the sciatic nerves of the AIDP-immunoglobulin-treated animals revealed loosening of myelin lamellae with widening of interperiod lines and multivesicular disruption of myelin. Vacuolar degeneration was detected in half of the nerves examined by light microscopy. Injection of AIDP-immunoglobulins for three days led to only minor changes, and mice receiving healthy human immunoglobulins showed no abnormalities. These data show that some features of AIDP can be transferred to mice by systemic administration of immunoglobulins and suggest that humoral factors have a pathogenic role in AIDP in addition to cellular factors.     

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.     

The gp120 glycoprotein of HIV-1 binds to sulfatide and to the myelin associated glycoprotein.

We investigated the binding of the gp120 glycoprotein of the human immunodeficiency virus (HIV-1) to neural glycolipids and glycoproteins by ELISA. The gp120 protein bound to sulfatide (GalS), a sulfated glycolipid autoantigen implicated in sensory neuritis, and to the myelin associated glycoprotein (MAG), an autoantigen in demyelinating neuropathy. Binding of gp120 to MAG was inhibited by the HNK-1 antibody, which recognizes a sulfated glucuronic acid epitope, suggesting that the interaction involves carbohydrate determinants. Sulfatide and MAG are potential receptors for gp120 in peripheral nerve and may have a role in the neuropathy associated with HIV-1 infection.     

Temporal expression pattern of peripheral myelin protein 22 during in vivo and in vitro myelination

Peripheral myelin protein 22 (PMP22) was initially described as a minor component of peripheral myelin. Mutations affecting the PMP22 gene cause demyelinating neuropathies, supporting a role for the protein in PNS myelination. Furthermore, PMP22 carries the L2/HNK-1 carbohydrate epitope suggesting an adhesion/recognition function. Despite advances in characterizing the PMP22 gene, the specific role(s) of the protein in myelin remains unknown. In this study we determined the temporal expression pattern of PMP22 in comparison to galactocerebroside (GalC) and myelin associated glycoprotein (MAG), early constituents of PNS myelin, and to protein zero (P0) and myelin basic protein (MBP), late components of myelin. In sciatic nerve lysates, PMP22 was detected at postnatal day 3, after MAG, but before MBP expression. The same results were obtained in cocultures of dorsal root ganglion neurons and Schwann cells (SCs). Low levels of PMP22 were found in early, anti-MAG and anti-GalC immunoreactive, myelinating cocultures. However, PMP22 could only be detected in the SC plasma membrane after basal lamina formation. In long-term myelinating cocultures PMP22 levels continued to increase and the protein was found in anti-P0 and anti-MBP immunoreactive myelin segments. Furthermore, PMP22, MBP, and P0 protein levels were greatly enhanced by progesterone treatment of the cocultures. The highest levels of PMP22 expression were associated with late stages of myelination; however the presence of the protein in nonmyelinating SCs and in SCs commencing myelination supports multiple roles for PMP22 in peripheral nerve biology.     

Demyelinating neuropathy and monoclonal IgM antibody to myelin-associated glycoprotein

We studied a patient with demyelinating neuropathy and monoclonal IgM kappa antibody to the major myelin-associated glycoprotein (MAG). Binding of this monoclonal antibody to the myelin antigen was demonstrated by immunoelectroblot. Binding to MAG seemed to be specific, because it was completely inhibited by MAG isolated from human myelin. Immunostaining was observed with MAG from CNS and peripheral nervous system myelin.     

Human monoclonal anti-MAG antibody and anti-Leu 7 recognise shared antigenic determinants in peripheral nerve and spinal cord.

Anti-Leu 7 monoclonal antibody (MAB), a marker of natural killer cells, and a human MAB to myelin-associated glycoprotein (MAG) from a patient with a demyelinating neuropathy specifically stained Schmidt-Lanterman incisures, paranodal and periaxonal regions in peripheral nerve myelin by immunocytochemistry on thin plastic sections, while compact myelin was labelled in paraffin-embedded material. Preabsorption studies indicated that the antigen recognised was a MAG epitope shared by MAG and Leu 7. In spinal cord both MABS bound to oligodendrocytes and a subclass of anterior horn cells. Our findings support the hypothesis that shared antigens between the nervous and the immune systems do exist in situ, which may be important in the pathogenesis of demyelinating neuropathies with monoclonal gammopathies.     

The electrodiagnostic findings in polyneuropathies associated with IgM monoclonal gammopathies.

Electrodiagnostic studies were analyzed in patients with neuropathy associated with IgM monoclonal proteins, 7 with anti-myelin associated glycoprotein reactivity (MAG) and 7 nonreactive to MAG. The findings were distinctly different in the two groups. The electrodiagnostic studies of all the MAG-reactive patients had demyelinating features with slowing of conduction and prolonged distal latencies while only one of the MAG-nonreactive patients had a demyelinating pattern. In fact, the MAG-nonreactive patients were a heterogeneous group, both electrodiagnostically and clinically. This study supports the concept that MAG-reactive polyneuropathy is demyelinating in type, and is caused by the activity of the IgM M-protein directed at an antigen in the myelin sheath.     

Immune reactive C3d on the surface of myelin sheaths in neuropathy

Immunofluorescence studies of sural nerve demonstrated immune reactive C3d and IgM on the surface of myelin sheaths in seven patients with neuropathy and an anti-myelin-associated glycoprotein (MAG) IgM M-protein. Similar deposits of C3d and sometimes IgM were found in four of six patients with acute or chronic inflammatory demyelinating polyneuropathy and in three of six patients with vasculitic neuropathy (including one with acquired immunodeficiency syndrome (AIDS)). C3d was not found in 80 patients with other peripheral nerve disorders except for two with metachromatic leukodystrophy. None of the C3d deposits contained immune reactive C3c implying substantial degradation of C3b. C3d is a sensitive index of complement activation in nerve and may be useful in classification of neuropathies.     

Delayed apperance of anti–myelin-associated glycoprotein antibodies in a patient with chronic demyelinating polyneuropathy

A patient who had a polyneuropathy compatible with a chronic inflammatory demyelinating polyneuropathy and was initially negative for anti-myelin-associated glycoprotein (MAG) antibodies developed a double monoclonal gammopathy, IgM kappa and IgM lambda, two years after the diagnosis. The IgM kappa, but not the IgM lambda, exhibited strong anti-MAG antibody activity. The late appearance of the anti-MAG immunoreactivity suggests that in patients with an initial diagnosis of chronic inflammatory demyelinating polyneuropathy, the search for anti-MAG antibodies should be repeated during the course of the neuropathy.     

亚低温治疗对实验性脑出血大鼠死亡率及脑组织钙含量的影响

目的本研究观察３２℃亚低温对实验性脑出血大鼠２４ｈ内死亡率和脑组织钙含量的影响。方法１３４只大鼠分成两部分：（１）６８只大鼠用于死亡率观察;（２）６６只大鼠用于脑组织钙含量测定。每一部分分成假手术对照组、常温脑出血组及亚低温脑出血组。结果常温组２４ｈ内死亡率为３６．６７％,亚低温组为４．５５％;脑组织钙含量常温组较对照组和亚低温组为高。结论亚低温治疗能显著减少实验性脑出血大鼠２４ｈ内死亡率,减少脑出血后脑组织钙含量。     

Immunocytochemical localization of MAG, MBP and P0 protein in acute and relapsing demyelinating lesions of Theiler''s virus infection

Acute demyelinating and relapsing demyelinating lesions from spinal cords of mice infected with the WW strain of Theiler's encephalomyelitis virus (TMEV) were studied immunocytochemically with antisera to various myelin constituents. Acute lesions were studied for differences in the distribution of myelin basic protein (MBP) and myelin associated glycoprotein (MAG). Relapsing lesions, characterized by demyelination of areas previously remyelinated by Schwann cells, were studied for differences in the distribution of P0 and MAG. In both instances the earliest lesions were characterized by preferential disappearance of MBP and P0 respectively when compared to MAG. In well-developed lesions, MAG, MBP and P0 were absent in essentially equal proportion. These observations are in agreement with previous findings suggesting a primary loss of myelin rather than a direct attack on oligodendrocytes as the main pathogenetic mechanism of demyelination in this viral model.     

IgM monoclonal gammopathy–associated neuropathies with different IgM specificity

Background and purpose: Antibodies directed against myelin‐associated glycoprotein (MAG) are believed to be the most frequent biologic marker of the neuropathies associated with IgM monoclonal gammopathy of undetermined significance (MGUS). The objective of this study was to examine the prevalence of antiganglioside and/or sulfatide‐positive patients and their clinical findings, including therapeutic response, compared to anti‐MAG‐positive or seronegative patients. Methods: We prospectively followed 46 patients with MGUS who were diagnosed in our tertiary referral centers for polyneuropathy since 1997. All patients underwent nerve conduction studies and were tested for anti‐MAG, gangliosides, and sulfatide antibodies. All the anagraphic and clinical data (including symptoms, disability scale, therapy, secondary malignancy development) were recorded in a database and compared between three patients’ groups (anti‐MAG‐positive; antiganglioside/sulfatide‐positive; no reactivity). Results: Anti‐MAG reactivity was present in 17 (37%) patients; other 17 patients (37%) had antiganglioside/sulfatide reactivity and 12 (26%) had no reactivity. Patients with antiganglioside/sulfatide positivity, although heterogeneous by a clinical and neurophysiological point of view, had the most severe neuropathic manifestations and a higher disability score at nadir (P < 0.001). These patients had a better response to both intravenous immunoglobulin therapy and rituximab. Conclusions: Our results suggest that antiganglioside/sulfatide‐positive patients form a relevant portion of patients with MGUS‐associated polyneuropathy seen in tertiary care centers and should be considered in future studies on treatment response.