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

A novel cell-based immunofluorescence assay for the detection of autoantibodies to myelin-associated glycoprotein

Peripheral neuropathy with antibodies to myelin-associated glycoprotein (MAG) is an autoimmune demyelinating disorder of the peripheral nervous system caused by pathogenic IgM recognizing the human natural killer-1 glycoepitope expressed on MAG. This study aimed to analyze the performance of a new indirect immunofluorescence cell-based assay (CBA, EUROIMMUN) for the detection of anti-MAG IgM. Antibody reactivity was determined in sera from 95 patients with clinical and neurophysiological evidence of anti-MAG-associated neuropathy and in control samples from 55 patients with other forms of peripheral neuropathy. Compared to the results of the gold standard method (ELISA, Bühlmann) and using samples at a dilution of 1:100, the CBA had a sensitivity of 98.9% and a specificity of 100% (PPV 100%, NPV 98.2%). In conclusion, the CBA allows the detection of antibodies to MAG using an easy and standardized technique, and it presents a sensitive and specific alternative to the more time-consuming ELISA. Larger studies are needed to address anti-MAG titer monitoring in parallel with clinical activity.

A diagnostic score for anti-myelin-associated-glycoprotein neuropathy or chronic inflammatory demyelinating polyradiculoneuropathy in patients with anti-myelin-associated-glycoprotein antibody

BACKGROUND AND PURPOSE

A diagnostic score was developed to discriminate anti-myelin-associated-glycoprotein (MAG) neuropathy from chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and applied it to patients with atypical anti-MAG neuropathy.

METHODS

The clinical and electrophysiological features of patients with a diagnosis of typical anti-MAG neuropathy were compared to those of patients with a diagnosis of CIDP. The association of each feature with the diagnosis was assessed in the two groups. Features showing a significant association with the diagnosis were included in a multivariable logistic regression model and adjusted odds ratios were estimated for each feature. A score ranging from 1 to 3 was applied to each feature based on the magnitude of the estimated odds ratios. The score was then applied to patients with a clinical diagnosis of CIDP who also had high anti-MAG antibody titers (CIDP-MAG).

RESULTS

Thirty-one anti-MAG neuropathy patients, 45 typical CIDP patients and 16 CIDP-MAG patients were included. Scores in anti-MAG antibody patients ranged from 1 to 5 and in CIDP patients from -7 to -1. Using the score, 4/16 CIDP-MAG patients were diagnosed to have anti-MAG neuropathy and 12/16 patients to have CIDP. Response to intravenous immunoglobulin in the CIDP-MAG patients classified as CIDP was similar to that of definite CIDP patients and higher than that of anti-MAG neuropathy patients.

CONCLUSIONS

Our score allowed an accurate discrimination to be made, amongst patients with anti-MAG antibodies, of those affected by CIDP and the patients with anti-MAG neuropathy. This score may help proper treatment to be chosen for patients with anti-MAG antibodies with a CIDP-like presentation.

Polyneuropathy Associated with IgM Monoclonal Gammopathy; Advances in Genetics and Treatment, Focusing on Anti-MAG Antibodies

With increasing age, the chances of developing either MGUS or polyneuropathy increase as well. In some cases, there is a causative relationship between the IgM M-protein and polyneuropathy. In approximately half of these cases, IgM targets the myelin-associated glycoprotein (MAG). This results in chronic polyneuropathy with slowly progressive, predominantly sensory neurological deficits and distally demyelinating features in nerve conduction studies. Despite the disease being chronic and developing slowly, it can cause considerable impairment. We reviewed English medical publications between 1980 and May 2022 on IgM gammopathy-associated polyneuropathy, with special attention to studies addressing the pathophysiology or treatment of anti-MAG polyneuropathy. Treatment options have been limited to a temporizing effect of intravenous immunoglobulins in some patients and a more sustained effect of rituximab but in only 30 to 55 percent of patients. An increase in our knowledge concerning genetic mutations, particularly the MYD88L265P mutation, led to the development of novel targeted treatment options such as BTK inhibitors. Similarly, due to the increasing knowledge of the pathophysiology of anti-MAG polyneuropathy, new treatment options are emerging. Since anti-MAG polyneuropathy is a rare disease with diverse symptomatology, large trials with good outcome measures are a challenge.

The evaluation and management of monoclonal gammopathy of renal significance and monoclonal gammopathy of neurological significance

Despite the benign nature of monoclonal gammopathy of undetermined significance (MGUS), mounting data are associating MGUS with the development of organ dysfunction, specifically monoclonal gammopathy of renal significance (MGRS) and monoclonal gammopathy of neurological significance (MGNS), which could be associated with substantial morbidity. Emerging evidence suggests that patients with MGRS and MGNS could benefit from treatments used for myeloma, Waldenström macroglobulinemia, or chronic lymphocytic leukemia, depending on the underlying pathology. However, the treatment of MGRS and MGNS is not standardized, and potentially effective therapies might not be reimbursed because these conditions do not formally meet the criteria for malignant processes. The present review aims at establishing standards for the evaluation and management of MGRS and MGNS, which can facilitate the diagnosis of and provide therapeutic options for treating practitioners and patients affected by these conditions. The careful design and execution of clinical trials for patients with MGRS and MGNS are positively encouraged.

Aberrant Expression of Nodal and Paranodal Molecules in Neuropathy Associated With IgM Monoclonal Gammopathy With Anti-Myelin-Associated Glycoprotein Antibodies

To clarify the pathogenesis of anti-myelin-associated glycoprotein (MAG) antibody neuropathy associated with IgM monoclonal gammopathy (anti-MAG neuropathy), sural nerve biopsy specimens from 15 patients were investigated. Sodium channels, potassium channels, contactin-associated protein 1 (Caspr1), contactin 1, and neurofascin were evaluated by immunofluorescence in teased-fiber preparations. Immunoreactivity to the pan-sodium channel in both anti-MAG neuropathy patients and in normal controls was concentrated at the node of Ranvier unless there was demyelination, which was defined as the widening of the node of Ranvier. However, this immunoreactivity became weak or disappeared as demyelination progressed. In contrast, KCNQ2 immunostaining was nearly absent even in the absence of demyelination. The lengths of Caspr1, contactin 1, and pan-neurofascin immunostaining sites at the paranode were significantly increased compared with those of normal controls despite the absence of demyelination. The length of paranodal neurofascin staining correlated with the anti-MAG antibody titer, nerve conduction indices, the frequency of de/remyelination in teased-fiber preparations, and the frequency of widely spaced myelin (p < 0.05, p < 0.05, p < 0.01, and <0.05, respectively). These findings suggest that nodal and paranodal molecular alterations occur in early stages preceding the morphological changes associated with demyelination in anti-MAG neuropathy.

Patient With 2 Hematologic Malignancies Presenting as Neurolymphomatosis

Peripheral nervous system damage from hematologic malignancies is related to neoplastic cells infiltration of peripheral nerves or to monoclonal antibody production cross-reacting with peripheral nerves' antigens. Neurolymphomatosis (NL), a rare manifestation of hematologic malignancies, occurs when malignant cells invade the peripheral nerves leading to various manifestations. Here, we report a case of NL with 2 hematologic malignancies in a 79-year-old woman presenting with lower extremity pain/weakness. Investigation revealed anemia, IgM kappa monoclonal gammopathy, and elevated anti-MAG titer. Electrodiagnostic studies were consistent with mononeuropathy multiplex while imaging suggested malignancy in her ovaries and right S1 nerve root. Bone marrow and ovarian biopsies revealed chronic myelomonocytic leukemia, Waldenstrom macroglobulinemia, and diffuse large B-cell lymphoma. She received standard chemotherapy resulting in radiographic resolution of disease and symptomatic relief. NL can precede the diagnosis of hematologic malignancy but its symptoms are not easily identifiable, whereas management depends on the treatment of the underlying tumor.

Investigation and management of IgM and Waldenström-associated peripheral neuropathies: recommendations from the IWWM-8 consensus panel

Paraproteinaemic neuropathies are a heterogeneous group of disorders most frequently associated with IgM monoclonal gammopathies including Waldenström macroglobulinaemia (WM). Their consequences are significant for affected patients, and their management challenging for their physicians. The variability in clinical presentation and time course hamper classification and management. The indications for invasive investigations such as cerebrospinal fluid analysis, nerve conduction tests and sensory nerve biopsies are unclear, and the optimum way to measure clinical response to treatment unknown. When to intervene and and how to treat, also present challenges to physicians. As part of its latest deliberations at the International Workshops on WM (IWWM) in London, UK (August 2014), the IWWM8 panel have proposed a consensus approach to the diagnosis and management of peripheral neuropathies associated with IgM monoclonal gammopathies, including WM. Importantly, a consensus regarding the use of clinical outcome measures and recommended models of care for this group of patients is discussed, as well as appropriate treatment interventions.

Neurologic autoimmunity: mechanisms revealed by animal models

Over the last decade, neurologic autoimmunity has become a major consideration in the diagnosis and management of patients with many neurologic presentations. The nature of the associated antibodies and their targets has led to appreciation of the importance of the accessibility of the target antigen to antibodies, and a partial understanding of the different mechanisms that can follow antibody binding. This chapter will first describe the basic principles of autoimmune inflammation and tissue damage in the central and peripheral nervous system, and will then demonstrate what has been learnt about neurologic autoimmunity from circumstantial clinical evidence and from passive, active, and occasionally spontaneous or genetic animal models. It will cover neurologic autoimmune diseases ranging from disorders of neuromuscular transmission, peripheral and ganglionic neuropathy, to diseases of the central nervous system, where autoantibodies are either pathogenic and cause destruction or changes in function of their targets, where they are harmless bystanders of T-cell-mediated tissue damage, or are not involved at all. Finally, this chapter will summarize the relevance of current animal models for studying the different neurologic autoimmune diseases, and it will identify aspects where future animal models need to be improved to better reflect the disease reality experienced by affected patients, e.g., the chronicity or the relapsing/remitting nature of their disease.

Paraneoplastic neuropathies

PURPOSE OF REVIEW

This review describes relevant advances in paraneoplastic neuropathies with emphasis on particular syndromes and the impact of new therapies.

RECENT FINDINGS

Sensory neuronopathy may present with symptoms that do not raise the suspicion of a paraneoplastic origin. A recent study on sensory neuronopathies of different causes identified paraneoplastic cases in a group of older (>60 years) male patients with subacute onset early pain, and frequent involvement of the arms. Paraneoplastic sensorimotor polyneuropathies may be confused with chronic inflammatory demyelinating polyneuropathy (CIDP) and in lymphomas with direct infiltration of nerves (neurolymphomatosis). Recent neurophysiological studies indicate that the polyneuropathy of POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M component, and skin changes) can be differentiated from CIDP by the presence of diffuse demyelination and more severe axonal loss. Neuropathy in Waldenström macroglobulinemia is heterogeneous. Up to 38% have demyelinating features and the rest show axonal degeneration due to different causes (dysimmune, amyloidosis, or tumoral infiltration). Isolated case reports suggest that the combination of cyclophosphamide and rituximab may be effective in paraneoplastic neuronopathies. Lenalidomide and dexamethasone are effective to control the neuropathy of POEMS patients who are not suitable for or progress after autologous stem cell transplantation.

SUMMARY

Clinical and neurophysiological studies are helpful to correctly identify particular paraneoplastic neuropathies.

Predicting treatment response in chronic, acquired demyelinating neuropathies

Chronic inflammatory demyelinating polyradiculopathy is an immune-mediated neuropathy that was first described approximately 30 years ago. Since that time an increasingly wide spectrum of chronic acquired demyelinating polyneuropathies exhibiting different phenotypes, clinical course and treatment responses to immunomodulatory treatment have been described. Several new therapeutic agents have been prescribed for such conditions, some with promising results. This review summarizes what is presently known about the clinical courses, treatment responses and predictors of response of the chronic inflammatory demyelinating polyradiculopathy subgroups.

Neuropathy and monoclonal gammopathy

The association of neuropathy with monoclonal gammopathy has been known for several years, even if the clinical and pathogenetic relevance of this association is not completely defined. This is not a marginal problem since monoclonal gammopathy is present in 1-3% of the population above 50 years in whom it is often asymptomatic, and in at least 8% of patients is associated with a symptomatic neuropathy, representing one of the leading causes of neuropathy in aged people. Monoclonal gammopathy may result from malignant lymphoproliferative diseases including multiple myeloma or solitary plasmocytoma, Waldenström's macroglobulinemia (WM), other IgM-secreting lymphoma or chronic lymphocytic leukemia, and primary systemic amyloidosis (AL). In most instances it is not associated with any of these disorders and is defined monoclonal gammopathy of undetermined significance (MGUS) for its possible, though infrequent, evolution into malignant forms. Several data support the pathogenetic role of the monoclonal gammopathy in the neuropathy particularly when of IgM isotype where IgM reactivity to several neural antigens has been reported. Increased levels of VEGF have been implicated in POEMS syndrome. However, there are as yet no defined therapies for these neuropathies, as their efficacy has not been confirmed in randomized trials.

Emerging drugs for Waldenström's macroglobulinemia

INTRODUCTION

Waldenström's macroglobulinemia (WM) is a rare but distinct B-cell lymphoproliferative disorder characterized by lymphoplasmacytic bone marrow infiltration and IgM monoclonal paraproteinemia. Alkylators or nucleosides analogs, often in combination with rituximab, are the most commonly used drugs, but WM will relapse and even salvage treatments may fail.

AREAS COVERED

We present recent advances on the treatment of WM, focusing on drugs that are under clinical investigation and for which data indicate promising activity and positive future prospects. Bortezomib is a proteasome inhibitor that eventually becomes a major treatment option for WM. Everolimus and perifosine which target mTOR (mammalian target of rapamycin) and Akt, respectively, of the PI3K/AKT/mTOR pathway showed some activity. Bendamustine, a novel alkylating agent is active, especially in combination with rituximab. Immunomodulatory drugs can act synergistically with rituximab but are toxic. Targeting surface antigens of the lymphoplasmatic cells have shown promising results.

EXPERT OPINION

Combinations of novel drugs with established agents are feasible and increase response rates but whether there will be an increase in the survival of patients with WM needs further investigation. The toxicity profile is an important determinant for the feasibility of these drugs in patients with WM.

Anti-myelin associated glycoprotein antibodies recognize HNK-1 epitope on CNS

Antibodies to myelin-associated glycoprotein (MAG) are associated with demyelinating polyneuropathy and are specific for the HNK-1 epitope. To test if anti-MAG IgM recognize HNK-1 on CNS, sera from 20 patients and 238 controls were tested on rat slices by indirect immunofluorescence (IIF). IgM from anti-MAG positive patients, but not from control sera, stained rat brain with perineuronal or neuropil pattern, depending on the CNS region. IIF titers significantly correlated with ELISA anti-MAG titers. The staining of patients' sera were inhibited by mouse anti-HNK-1 monoclonal antibody. Our results demonstrate that anti-MAG IgM recognizes HNK-1 outside the peripheral nerve myelin carriers.

Distinct cytokine patterns associated with different forms of chronic dysimmune neuropathy

To better understand the presumed immune system dysregulation of chronic dysimmune neuropathy (CDN) patients, we designed a study to evaluate the levels of pro- and anti-inflammatory cytokines in the most common forms of CDN: chronic inflammatory demyelinating polyneuropathy (CIDP), and anti-myelin-associated glycoprotein (MAG)-related polyneuropathy (MAGnp). Sixteen patients fulfilled diagnostic criteria for CIDP, 14 were diagnosed with MAGnp, and 36 were classified as exhibiting "chronic idiopathic polyneuropathy" (CIP). Cytokine production in mitogen-stimulated peripheral blood mononuclear cells (PBMCs) was analyzed by flow cytometry. CIDP and MAGnp patients were compared with CIP patients, those with monoclonal gammopathy without polyneuropathy (MGUS), and healthy controls (HC). We observed an increase in pro-inflammatory cytokines in the CIDP group, whereas interleukin-10 (IL-10) was augmented in the MAGnp patients. These distinctive immune alterations may represent a biological tool in differential diagnosis and future therapeutic approaches.

Pupil-involving third nerve palsy as a manifestation of anti-myelin-associated glycoprotein neuropathy

A 56-year-old man developed a pupil-involving left third nerve palsy. Imaging studies of the brain and intracranial vessels were normal. Neurological examination demonstrated a sensory polyneuropathy and mild distal weakness. Nerve conduction studies showed prolonged distal motor latencies. An enzyme-linked immunosorbent assay test detected high titers of anti-myelin-associated glycoprotein (MAG) antibodies. The patient improved with prednisone and rituximab treatment. Anti-MAG neuropathy should be considered when evaluating a patient with an undiagnosed cranial neuropathy, especially in the setting of a sensory neuropathy.

Central nervous system involvement in patients with monoclonal gammopathy and polyneuropathy

BACKGROUND AND PURPOSE

To evaluate clinical presentation of patients with the clinical triad of monoclonal gammopathy, polyneuropathy and signs of CNS involvement.

METHODS

Nineteen patients with monoclonal protein (M-protein, 9 IgM, 10 IgG) were studied. Clinical examination, MRI, cerebrospinal fluid analysis and immune reactivity against myelin-associated glycoprotein and gangliosides in serum were obtained. By immunohistochemistry, different binding patterns of M-proteins to human CNS tissue were investigated.

RESULTS

Nine out of 19 patients (four IgM, five IgG) showed one or more clinical signs of CNS involvement. Clinical features associated with signs of CNS pathology were disease duration and greater concentration of IgM paraprotein. The IgM M-protein of two patients strongly stained the cortex/cerebellar neurons in human brain sections.

CONCLUSION

Our results complement previous reports that some patients with monoclonal gammopathy and polyneuropathy can develop solitary or disseminated signs of CNS involvement. It indicates that pathological effects of M-proteins are not necessarily restricted to the peripheral nervous system. The specificity and affinity of circulating M-protein to antigens in the CNS might be critical for the development of different clinical phenotypes.

Peripheral neuropathies in Waldenström's macroglobulinaemia

OBJECTIVE

We sought to determine the prevalence, clinical features, and laboratory characteristics of polyneuropathies in Waldenström's macroglobulinaemia (WM), a malignant bone marrow disorder with lymphocytes that produce monoclonal IgM.

METHODS

We prospectively studied 119 patients with WM and 58 controls. Medical history was taken, and neurological examinations, electrodiagnostic tests, and serum studies were performed by different examiners who were blinded to results except the diagnosis of WM.

RESULTS

Polyneuropathy symptoms, including discomfort and sensory loss in the legs, occurred more frequently (p<0.001) in patients with WM (47%) than in controls (9%). Patients with WM had 35% lower quantitative vibration scores, and more frequent pin loss (3.4 times) and gait disorders (5.5 times) than controls (all p<0.001). Patients with IgM binding to sulphatide (5% of WM) had sensory axon loss; those with IgM binding to myelin associated glycoprotein (MAG) (4% of WM) had sensorimotor axon loss and demyelination. Patients with WM with IgM binding to sulphatide (p<0.005) or MAG (p<0.001) had more severe sensory axon loss than other patients with WM. Demyelination occurred in 4% of patients with WM with no IgM binding to MAG. Age related reductions in vibration sense and sural SNAP amplitudes were similar ( approximately 30%) in WM and controls.

CONCLUSIONS

Peripheral nerve symptoms and signs occur more frequently in patients with WM than controls, involve sensory modalities, and are often associated with gait disorders. IgM binding to MAG or sulphatide is associated with a further increase in the frequency and severity of peripheral nerve involvement. Age related changes, similar to those in controls, add to the degree of reduced nerve function in patients with WM.

IgM paraproteinaemic neuropathies

PURPOSE OF REVIEW

To conduct a critical review of recent studies on the pathogenesis and treatment of IgM paraproteinaemic neuropathies and analyse their implication for patient management.

RECENT FINDINGS

A better definition and classification of IgM monoclonal gammopathies has led to recommendations on therapeutic strategies for these patients, particularly for those with the asymptomatic form of Waldenström macroglobulinemia. Studies on the pathogenetic role of IgM paraprotein in neuropathy have led to the identification of a novel antibody reactivity against trisulfated heparin disaccharide, which was associated with painful, predominantly sensory, axonal distal neuropathy. Pathological studies on patients with axonal polyneuropathy and no antibody reactivity of the IgM paraprotein have shown that vasculitis may play an important role in this form of neuropathy, as possibly confirmed by its positive response to steroids. A number of open pilot trials have addressed the effect in IgM paraproteinaemic neuropathies of the humanized monoclonal antibody (rituximab) directed against the CD20 antigen. Even if the results of these studies are less promising than initially hoped, they provide evidence that rituximab may be effective in some patients with this neuropathy.

SUMMARY

New insights into the pathogenesis of axonal forms of IgM paraproteinaemic neuropathy have derived from the identification of novel antibody reactivity and of vasculitis. The latter finding may justify the use of steroids, otherwise ineffective in IgM paraproteinaemic neuropathy. Rituximab has opened the way to more selective and apparently safer immune therapies for this neuropathy, but its efficacy needs to be confirmed by randomized controlled trials.

Immunodetection of anti-MAG IgM antibody by cross-reactivity to LA-N-1 neuroblastoma cells

Demyelinating polyneuropathiy associated with IgM paraproteinemia and high titers of anti-MAG IgM antibodies (MAG-PN) is considered different from chronic inflammatory demyelinating polyneuropathy, particularly because of the poorer response to treatment of MAG-PN patients. Therefore, anti-MAG anitbodies may have relevant prognostic value. Available anti-MAG antibody assays require central nervous system myelin proteins from autopsied human brains. This study investigated the feasibility of detecting anti-MAG antibody by immunofluorescence and flow cytometry using a panel of human neuroblastoma cell lines as targets. We report here on the evaluation of the LA-N-1 cell line as an appropriate substrate for the detection of anti-MAG antibody by indirect immunoflourescence.

Different clinical, electrophysiological and immunological features of CIDP associated with paraproteinaemia

Chronic inflammatory demyelinating polyneuropathy (CIDP) is frequently associated with monoclonal gammopathies of undetermined significance (MGUS), Waldenström disease and osteosclerotic myeloma. There are still controversies about the role of these paraproteinaemias in determining the clinical features and the response to treatment of CIDP. We review the clinical, electrophysiological and immunological features and the response to treatment of patients with CIDP associated with paraproteinaemias. The available literature suggest some conclusions: presence of antimyelin-associated glycoprotein (MAG) antibody (Ab) identifies patients with mainly sensory CIDP and low response to treatment; CIDP associated with IgM-paraproteinaemia without anti-MAG Ab probably are similar to CIDP not associated with paraproteinaemia as well as CIDP with IgG- or IgA-MGUS; however, some patients with IgA-MGUS can show features similar to CIDP with IgM paraproteinaemia and anti-MAG Ab. Low response to immunomodulating treatment in patients with mainly motor CIDP should prompt a careful research of an underlying osteosclerotic myeloma.

Terminal latency index in polyneuropathy with IgM paraproteinemia and anti-MAG antibody

Criteria for the diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) are met by the polyneuropathy associated with immunoglobulin M (IgM) paraproteinemia and anti-myelin-associated glycoprotein (MAG) antibody (MAG-CIDP). However, MAG-CIDP differs from other types of CIDP, mainly in its poorer response to treatment. The utility of terminal latency index (TLI) as an electrophysiological marker for MAG-CIDP has been debated. In this study we confirmed its diagnostic usefulness and evaluated TLI threshold values for motor nerves investigated in routine nerve conduction studies. Median, ulnar, peroneal, and tibial TLIs of 11 subjects with MAG-CIDP, 18 with CIDP, and 76 healthy controls were compared, and threshold values for MAG-CIDP evaluated as the lowest value with a likelihood ratio higher than 10. Mean TLI values and TLIs of all but the peroneal nerve were significantly lower in MAG-CIDP. Median nerve TLI of 0.26 and ulnar nerve TLI of 0.33 were identified as the threshold TLI values for MAG-CIDP.

Anti-GM(2) IgM antibody-induced complement-mediated cytotoxicity in patients with dysimmune neuropathies

Anti-GM2 IgM antibodies have been reported in some patients with dysimmune neuropathy or lower motor neuron syndrome. To determine whether these antibodies can induce complement-dependent cytolysis we performed a cytotoxicity assay on neuroblastoma cells with sera from seven patients with demyelinating dysimmune neuropathies and high titers of anti-GM2 IgM. As controls we used sera from seven patients with other anti-neural reactivities, six with the same neuropathies but no anti-GM2 or other anti-neural reactivity and from eight normal subjects. Of the seven positive sera tested, six induced complement-mediated cytotoxicity, while none of the controls had any relevant effect on neuroblastoma cells. Preincubation of positive sera with purified GM2 removed cytotoxic activity. Affinity purified anti-GM2 IgM had the same cytotoxic anti-GM2 effect of whole serum while serum or complement alone did not have any effect. In four anti-GM2-positive patients the percentage of cell lysis correlated with anti-GM2 titers and with IgM staining of neuroblastoma cells while in two the cytotoxic effect was higher than expected from antibody titers. Complement-mediated cell lysis induced by anti-GM2 IgM antibodies may be a possible mechanism of neural damage in patients with dysimmune neuropathy and high titers of anti-GM2 IgM antibodies.

Diagnostic criteria for demyelinating polyneuropathy associated with monoclonal gammopathy

In order to define diagnostic criteria for the demyelinating polyneuropathy associated with monoclonal gammopathy of undetermined significance (MGUS), we compared 30 patients with idiopathic chronic inflammatory demyelinating polyneuropathy (CIDP) without a monoclonal gammopathy, with 29 patients with polyneuropathy associated with MGUS. All 59 patients fulfilled research criteria for CIDP. In the patients with MGUS, sensory symptoms and signs predominated, there was usually no cranial nerve involvement, and the neuropathy was symmetrical with a slowly progressive course. On electrophysiological examination, an abnormal median nerve sensory action potential in combination with a normal sural nerve action potential (AMNS) was not found. In idiopathic CIDP patients, a preceding infection was frequent, motor features predominated, there was often cranial nerve involvement, the neuropathy could be asymmetrical, and AMNS was frequently found. Diagnostic criteria for demyelinating polyneuropathy associated with MGUS are presented.

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.

Anti-MAG and anti-SGPG antibodies in neuropathy

We compared the binding of human antibodies from patients with neuropathy to the myelin-associated glycoprotein (MAG), to its cross-reactive glycolipid sulfoglucuronyl paragloboside (SGPG), and to sections of peripheral nerve. Titers were correlated with the clinical presentation and results of electrophysiological and pathological studies. Most patients had a predominantly sensory or sensorimotor demyelinating neuropathy and highly elevated antibodies to both MAG and SGPG, but 2 had highly elevated antibodies to MAG alone, and 1 to SGPG alone. Two patients had predominantly motor neuropathy and highly elevated antibodies to SGPG which reacted with MAG by Western blot but not by enzyme-linked immunosorbent assay. One patient had amyotrophic lateral sclerosis and antibodies to SGPG but not to MAG. These studies indicate that the neuropathic syndrome associated with anti-MAG or -SGPG antibodies are more heterogeneous than previously suspected, and that although most of the antibodies react with both MAG and SGPG, some may react with MAG or SGPG alone.

Neuropathies associated with monoclonal gammopathies

Approximately 10% of patients with idiopathic peripheral neuropathy have an associated serum monoclonal gammopathy or M-protein. This represents six times the incidence of M-proteins found in the general population. In 5% of idiopathic peripheral neuropathy patients the M-protein is associated with an identifiable plasma cell dyscrasia. Sclerotic myeloma is particularly important to recognize because treatment may result in amelioration of the neuropathy and remission of the tumor. Patients with primary systemic amyloidosis often have preferential small fiber involvement with a dissociated sensory loss and autonomic dysfunction. The nerve root infiltration of lymphoproliferative disorders may simulate a polyradiculoneuropathy. In cases without an identifiable cause for the M-protein, referred to as monoclonal gammopathy of undetermined significance (MGUS), the pathophysiologic basis for the neuropathy is poorly defined in most cases. A role for M-proteins with antibody activity to myelin-associated glycoprotein is provocative. This review summarizes current knowledge of this important group of disorders.

Anti-alpha- and beta-tubulin IgM antibodies in dysimmune neuropathies

An increased frequency of serum IgM antibodies to beta-tubulin has been found by ELISA in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and the Guillain-Barré syndrome (GBS). We used an immunoblot technique to compare the frequency, titer and specificity of anti-tubulin IgM antibodies in 207 patients with different neuropathies, 109 with other neurological disease (OND) and 110 non-neurological controls. High titers of serum anti-tubulin IgM antibodies (> 1:1600) were present in 2 patients with CIDP (10.5%), 1 with multifocal motor neuropathy (MMN) (11%), 1 with GBS (1.8%), two with IgM monoclonal gammopathy, one with (1.3%) and one without neuropathy (2.1%), and in two with OND (1.8%). Even if the relative binding to alpha- and beta-tubulin differed among positive patients, in all IgM bound to both tubulin subunits. All positive patients had a similarly intense IgM reactivity with tubulin by ELISA that showed high anti-tubulin IgM in 4 additional CIDP patients (total positive by ELISA 30%) and in 7 of 23 normal subjects (30%). Even if high anti-tubulin IgM were slightly more frequent by immunoblot in chronic dysimmune neuropathies than in other diseases, possibly reflecting a secondary response to neural damage during an ongoing immune response, their relatively low frequency in these diseases does not seem to justify their measurement for diagnostic application.

CD5 expression on B cells may be an activation marker for secretion of anti-myelin antibodies in patients with polyneuropathy associated with monoclonal gammopathy

B cells expressing the CD5 marker belong to a subpopulation with potential autoreactive properties. Increased proportions of CD5+ B cells have been reported in autoimmune diseases. In patients with monoclonal gammopathy and demyelinating polyneuropathy, the M-component often consists of autoantibodies reacting with myelin components. We therefore investigated if CD5+ B cells were involved in the production of anti-myelin antibodies. There was no difference of mean value of CD5+ B cells between patients and controls. However, the proportion of CD5+ B cells was significantly correlated with the amount of anti-myelin antibodies. In seven patients, CD5+ B cells were enriched using an immunomagnetic technique. The number of CD5+ and CD5- B cells secreting anti-myelin antibodies was determined by ELISPOT. In two patients with high levels of antibodies, antibody-secreting cells were mainly, but not exclusively, CD5+ B cells. In five patients with low levels of antibodies, most cells secreting anti-myelin antibodies were CD5-. We conclude that CD5 expressed on B cells may be an activation marker, reflecting B cells producing high amounts of anti-myelin antibodies in patients with polyneuropathy associated with monoclonal gammopathy.

Avidity distribution of antibodies against peripheral nerve myelin in patients with polyneuropathy associated with IgM monoclonal gammopathy and in healthy controls

To elucidate the role and nature of antibodies against peripheral nerve myelin (PNM) we studied their avidity distribution. Twelve patients with demyelinating polyneuropathy associated with IgM monoclonal gammopathy were compared with 12 healthy blood donors previously found to have anti-PNM antibodies of IgM isotype. For comparison, the avidity distribution of IgM antibodies against the varicella zoster antigen in 10 patients with herpes zoster infection was also studied. Microtitre plates containing antibody bound to antigen were exposed to increasing concentrations of sodium thiocyanate (NaSCN) followed by an ELISA assay. NaSCN changes the ion strength and the pH, and thereby the critical conditions for antibody-antigen binding. Resistance to NaSCN was used as a measure of antibody avidity. Anti-PNM antibodies from patients with monoclonal gammopathy were of predominantly low avidity whereas antibodies from blood donors were of predominantly high avidity. Avidity index, representing the molar concentration of NaSCN required to reduce the initial absorbance values by 50%, was on average 11.7 times higher in blood donors (range 0.24-2.65, mean = 0.82) than in patients with monoclonal gammopathy (range 0.04-0.10, mean = 0.07) (p = 0.002). On the other hand, patients with monoclonal gammopathy had on average a 100-fold higher relative concentration of antibodies against PNM compared to blood donors (range 4.1-392.6 AU, mean 85.0 AU, and range 0.2-1.7 AU, mean 0.85 AU, respectively) (p = 0.002). Antibodies against the varicella zoster antigen from patients with herpes zoster showed a high avidity index (range 0.25-2.6, mean = 1.24). Using Western blot, several 14-30 kDa proteins in PNM were found to be the target antigen for IgM anti-PNM antibodies in both patients with monoclonal gammopathy and polyneuropathy, and in blood donors.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathogenesis and therapy of neuropathies associated with monoclonal gammopathies

Approximately 10% of patients with peripheral neuropathy of otherwise unknown etiology have an associated monoclonal gammopathy. Both the neuropathies and the monoclonal gammopathies in these patients are heterogeneous, but several distinct clinical syndromes that may respond to specific therapies can be recognized. It is important to recognize these syndromes because monoclonal gammopathies also occur in 1% of the normal adult population, and in some cases, monoclonal gammopathies are coincidental and unrelated to the neuropathy. In patients with IgM monoclonal gammopathies, IgM M proteins frequently have autoantibody activity and are implicated in the pathogenesis of the neuropathy. IgM M proteins that bind to myelin-associated glycoprotein (MAG) have been shown to cause demyelinating peripheral neuropathy; anti-GM1 antibody activity is associated with predominantly motor neuropathy, and anti-sulfatide or chondroitin sulfate antibodies are associated with sensory neuropathy. The IgM monoclonal gammopathies may be malignant or nonmalignant, and polyclonal antibodies with the same specificities are associated with similar clinical presentations in the absence of monoclonal gammopathy. IgG or IgA monoclonal gammopathies are associated with neuropathy in patients with osteosclerotic myeloma or the POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy myeloma, and skin changes). Amyloidosis or cryoglobulinemic neuropathies can occur with either IgM or IgG and IgA monoclonal gammopathies. Therapeutic intervention depends on the specific clinical syndrome but is generally directed at removing the autoantibodies, reducing the number of monoclonal B cells, and interfering with the effector mechanisms.

Late motor involvement in cases presenting as "chronic sensory demyelinating polyneuropathy"

Chronic inflammatory demyelinating polyneuropathy (CIDP) is usually characterized by prominent motor deficits. A pure sensory presentation, labeled chronic sensory demyelinating neuropathy (CSDN), has been reported, but it is unclear if this neuropathy is a distinct clinical and immunologic entity or merely the sensory presentation of the more usual sensorimotor CIDP. We describe 5 patients with what initially appeared to be CSDN; 3 subsequently developed substantial weakness coincident with the electrophysiologic appearance of multifocal motor conduction block. These cases indicate that, in some cases, CSDN may be a transitional clinical stage of CIDP in which the more usual sensorimotor deficits develop later. Immune-based therapy, including intravenous immunoglobulin, was found to be effective in both the pure sensory and sensorimotor types.

Autoantibodies to cerebroside sulphate (sulphatide) in leprosy

Sera from 40 leprosy patients were screened for autoantibodies to cerebroside sulphate (sulphatide). Anti-sulphatide IgM in groups of patients with lepromatous (LL) and borderline (BL + BB + BT), but not with tuberculoid (TT) disease, were significantly elevated above the levels found in endemic control subjects. Eight-six percent (18 out of 21; mean 1.59 OD units) of LL, 33% (four out of 12; mean 1.08 OD units) of borderline and 13% (one out of eight; mean 0.69 OD units) of tuberculoid patients had anti-sulphatide IgM in their sera above a cut-off value of 2 s.d. above the mean value (0.66 OD units) for control sera. Elevated anti-sulphatide IgG was detected in only one patient's serum, an individual with LL disease. The level of anti-sulphatide IgM was strongly correlated to expression of the TH3 idiotype, an idiotype previously defined by a human MoAb that bound Mycobacterium leprae phenolic glycolipid, Klebsiella capsular polysaccharide, polynucleotides and human tissues. The purified, TH3 MoAb was found in this study to bind sulphatide, but not cholesterol-3-sulphate or cerebroside. It is suggested that anti-sulphatide IgM is elevated in leprosy, in relation to the bacterial load. Anti-sulphatide IgM fell at the onset of erythema nodosum leprosum (ENL) reaction, consistent with the deposition of serum antibodies, and thus may play a part in pathology during periods of inflammation, particularly in multibacillary patients.

Gangliosides and allied glycosphingolipids in human peripheral nerve and spinal cord

Glycosphingolipids were determined in human spinal cord, cauda equina and femoral nerve of 10 subjects aged 20-70 years and in dorsal and ventral roots of four subjects aged 17-60 years. Myelin was isolated from corresponding tissue. Axons were isolated from the four specimens of dorsal and ventral roots. The concentration (mean and standard error of mean) of gangliosides in spinal cord was 0.80 +/- 0.03 mumol sialic acid/g fresh tissue, in cauda equina 0.40 +/- 0.02 mumol/g and in femoral nerve 0.23 +/- 0.01 mumol/g. In spinal cord only trace amounts of glycosphingolipids of the lacto series were found, and the ganglioside pattern differed from that in cerebral white matter by a relatively high proportion of GD3 and a low proportion of GD1a. The ganglioside patterns were almost identical in cauda equina and femoral nerve--the major ganglioside being 3'-LM1, 0.07 and 0.04 mumol/g respectively. Another ganglioside of the lacto series, 3'-HexLM1, was 25% of 3'-LM1. Peripheral nerve also contained three acidic glycosphingolipids in addition to sulfatide--LK1 and HexLK1 belonging to the glycosphingolipid lacto series and containing glucuronyl-3-sulfate instead of sialic acid, and inositolphosphoryl galactosylceramide. The dorsal (sensory) and ventral (motor) roots had the same major membrane lipid composition but the ganglioside concentration was 30% higher in sensory than motor nerve and myelin. The patterns of gangliotetraose gangliosides were, however, the same in motor and sensory myelin and axons. The ceramide composition of the gangliosides is also reported.

Frequency and clinical correlates of anti-neural IgM antibodies in neuropathy associated with IgM monoclonal gammopathy

We studied the frequency and clinical correlates of different IgM specificities in 75 patients with neuropathy associated with IgM monoclonal gammopathy. Patients were tested for IgM reactivity with the myelin-associated glycoprotein, P0, neurofilaments, and tubulin by immunoblot; with GM1, asialo-GM1, GM2, GD1a, GD1b, sulfatide, and chondroitin sulfate C by enzyme-linked immunosorbent assay; and with brain and nerve glycolipids by overlay high-performance thin-layer chromatography. Forty-two patients (56%) had high titers of IgM antibodies to MAG; 4 (5%), to sulfatide (1 also to myelin-associated glycoprotein); 4 (5%), to the 200-kd neurofilament (2 also to myelin-associated protein); and 1 each, to GD1b and chondroitin sulfate C. No reactivity was found in 26 patients (35%). More patients with anti-myelin-associated glycoprotein IgM (62%) than with unknown IgM reactivity (31%) had a predominantly sensory neuropathy (p < 0.025). Nerve conduction findings were consistent with a demyelinating neuropathy in 77% of patients reactive to myelin-associated glycoprotein and 24% with unknown reactivity (p < 0.0001) and the mean conduction velocity of peroneal nerve was lower in the former group (22.9 m/sec) than in the latter group (39.6 m/sec) (p < 0.000001). Patients with anti-sulfatide IgM had a sensorimotor neuropathy with morphological evidence of demyelination while anti-neurofilament IgM was not associated with homogeneous findings. Patients with anti-GD1b or anti-chondroitin sulfate C IgM had a predominantly motor impairment. The frequent occurrence of anti-neural IgM antibodies in neuropathy associated with IgM gammopathy, and their frequent, though not constant association with similar neuropathy features, support their possible pathogenetic role in the neuropathy.

Serum IgG antibodies to a 35-kDa P0-related glycoprotein in motor neuron disease

Using an immunoblot technique we found a significantly higher frequency of serum IgG antibodies to a 35-kDa peripheral nerve myelin glycoprotein in patients with motor neuron disease (MND) (39% of 70) than in patients with neuropathy (13% of 61), other neurological disease (9% of 32) and normal subjects (5% of 20) (P < 0.005 in all cases), but not with multiple sclerosis (MS) (20% of 30) or non-neural immune diseases (25% of 32). Most positive patients had antibody titers of 1:200 or 1:2000 while higher titers were only found in seven patients with MND, one with chronic inflammatory demyelinating neuropathy, two with MS, two with non-neural immune diseases and one with stroke. The reacting protein had a higher molecular mass than P0 and was only faintly bound by an anti-P0 antiserum, but had the same N-terminal amino acid sequence of P0. The difference in molecular mass between P0 and the 35-kDa protein and the IgG reactivity of one patient's IgG with the 35-kDa protein persisted after its deglycosylation and dephosphorylation. Although there is no evidence that these antibodies are pathogenic, their frequent occurrence in MND and other immune-mediated conditions supports the hypothesis of an activation of the immune system in MND.

Increased incidence of paraproteinemia and autoantibodies in patients with normal-pressure glaucoma

We assessed the incidence of paraproteins and autoantibodies in 44 patients (mean age, 65.3 +/- 1.9 years) with normal-pressure glaucoma and 41 patients (mean age, 68.8 +/- 1.8 years) monoclonal proteins occurred more often (P = .0047) in patients with normal-pressure glaucoma (eight of 44, 18%) than in control subjects with primary open-angle glaucoma (zero of 41, 0%). Autoantibodies to extractable nuclear antigens, most often Sjögren's syndrome A antigen (SSA[Ro]), were also found more frequently (P = .0022) in patients with normal-pressure glaucoma (13 of 44, 30%) than in control subjects (one of 41, 2%). Paraproteins and autoantibodies to extractable nuclear antigens generally occurred in different patients with an overall incidence of 20 of 44 (45%) patients with normal-pressure glaucoma. In contrast, no significant difference in the incidence of antinuclear antibodies existed between the groups. These findings suggest that humoral immune mechanisms may have a role in the pathogenesis of optic neuropathy in patients with normal-pressure glaucoma.

Peripheral neuropathy in IgM monoclonal gammopathy and Wäldenstrom's macroglobulinemia: a frequent complication in elderly males with low MAG-reactive serum monoclonal component

Peripheral neuropathy (PN) is a frequent complication during primary macroglobulinemia (PM), whose immunological genesis has been suggested by various authors. This study involved 65 PM patients (44 men and 21 women aged 35-78), diagnostically divided into MGUS (31 cases), and indolent (IWM, 24 cases) or symptomatic (WM, 10 cases) Waldenstrom macroglobulinemia groups. All patients underwent neurological examination, including electrodiagnostic evaluation and the determination of the serum titre of antimyelin-associated glycoprotein (MAG). An evaluation was made of the prevalence of PN and its correlation with a series of hematological variables. The prevalence of PN was 31.6%: of those with PN, 73.1% manifested both clinical and electrophysiological signs of PN, primarily of the demyelinating type. Significant correlations emerged between the presence of PN and sex (M vs. F P = 0.0001), advanced age (P = 0.049), low MC levels (P = 0.025), high anti-MAG titres (P = 0.001) and high Hb levels (P = 0.001). No significant correlation with the diagnostic definition of PM was found, although the majority of cases with (particularly demyelinating) PN were MGUS or IWM. At multivariate analysis, the presence of PN significantly correlated with sex (P = 0.0001), age (P = 0.019), and anti-MAG titre (P = 0.001). Ten of the 26 PN cases showed no MAG reactivity. Significant correlations between PN and low serum MC levels/high MAG reactivity support the hypothesis of the antibody-mediated origin of many PN, and that the presence of PN depends on the characteristics of the proliferating pathological B clone, rather than on the tumor burden of the form of macroglobulinemia. Clinically, our data reconfirm the frequency of PN during PM and indicate simple clinicohematological variables useful for identifying patients at high neuropathic risk.

Immunofixation superior to plasma agarose electrophoresis in detecting small M-components in patients with polyneuropathy

Monoclonal immunoglobulins (M-components) in blood are found in some patients with polyneuropathy and are thought to be of pathogenetic importance, especially if the M-component is of IgM isotype. As the finding of an M-component may indicate a treatable polyneuropathy, the potential of the method to uncover an M-component is of importance. Cellulose acetate or agarose electrophoresis used in routine practice may miss small M-components covered by other proteins. We therefore applied the uncovering and specific method of immunofixation in comparison with agarose electrophoresis on patients investigated for polyneuropathy. Of 83 consecutive patients, 5 had M-components. Two of these 5 patients, one with an axonal polyneuropathy and the other with a lower motor neuron syndrome, had extra bands on agarose electrophoresis, verified as IgG M-components by immunofixation. In the 3 additional patients an M-component was uncovered only by immunofixation, not seen in the agarose electrophoresis of plasma; 2 of them were of IgM isotype and one was of IgG isotype. These 3 patients were diagnosed as having a demyelinating (i.e., possibly immune-mediated) polyneuropathy by means of neurophysiology and in one by means of nerve biopsy. A 6th patient had 2 small bands in the gamma region on the agarose electrophoresis, verified as oligoclonal bands of IgG isotype by immunofixation but was not judged as an M-component. Three out of the 83 patients, were judged as having motor neuron diseases. All remaining 80 were found to have polyneuropathy.(ABSTRACT TRUNCATED AT 250 WORDS)