Ganglioside GD1b is the target antigen for a biclonal IgM in a case of sensory-motor axonal polyneuropathy: involvement of N-acetylneuraminic acid in the epitope

CANOMAD: a neurological monoclonal gammopathy of clinical significance that benefits from B-cell-targeted therapies

CANOMAD (chronic ataxic neuropathy, ophthalmoplegia, immunoglobulin M [IgM] paraprotein, cold agglutinins, and disialosyl antibodies) is a rare syndrome characterized by chronic neuropathy with sensory ataxia, ocular, and/or bulbar motor weakness in the presence of a monoclonal IgM reacting against gangliosides containing disialosyl epitopes. Data regarding associated hematologic malignancies and effective therapies in CANOMAD are scarce. We conducted a French multicenter retrospective study that included 45 patients with serum IgM antibodies reacting against disialosyl epitopes in the context of evocating neurologic symptoms. The main clinical features were sensitive symptoms (ataxia, paresthesia, hypoesthesia; n = 45, 100%), motor weakness (n = 18, 40%), ophthalmoplegia (n = 20, 45%), and bulbar symptoms (n = 6, 13%). Forty-five percent of the cohort had moderate to severe disability (modified Rankin score, 3-5). Cold agglutinins were identified in 15 (34%) patients. Electrophysiologic studies showed a demyelinating or axonal pattern in, respectively, 60% and 27% of cases. All patients had serum monoclonal IgM gammopathy (median, 2.6 g/L; range, 0.1-40 g/L). Overt hematologic malignancies were diagnosed in 16 patients (36%), with the most frequent being Waldenström macroglobulinemia (n = 9, 20%). Forty-one patients (91%) required treatment of CANOMAD. Intravenous immunoglobulins (IVIg) and rituximab-based regimens were the most effective therapies with, respectively, 53% and 52% of partial or better clinical responses. Corticosteroids and immunosuppressive drugs were largely ineffective. Although more studies are warranted to better define the optimal therapeutic sequence, IVIg should be proposed as the standard of care for first-line treatment and rituximab-based regimens for second-line treatment. These compiled data argue for CANOMAD to be included in neurologic monoclonal gammopathy of clinical significance.

Anti-ganglioside antibodies in amyotrophic lateral sclerosis revisited

BACKGROUND

Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disorder with typical onset in the 5th- 6th decade of life. The hypothesis of an autoimmune origin of ALS receives less attention today, but immunological phenomena still seem to be involved and mechanisms such as protective autoimmunity may be important. Detection of antibodies against a variety of gangliosides has been repeatedly described in ALS-patients by several authors, but widely differing frequencies and titres have been reported. Therefore, we investigated the presence of six common antibodies with a commercially available test panel for GA1, GM1, GM2, GD1a, GD1b and GQ1b in a large group of clinically well-characterized ALS patients and compared them to a collective of 200 healthy blood donors.

METHODS

IgG and IgM antibodies to the six gangliosides asialoGM1 (GA1), GM1, GM2, GD1a, GD1b, GQ1b were determined by GanglioCombi ELISA in sera of 84 ALS patients. Results were expressed as a %-ratio of a highly positive control and categorized as negative (<30%), borderline (30-50%), moderately (50-100%) and strongly positive (>100%). The values obtained from 200 Swiss blood donors served as a reference group.

RESULTS

In twenty-two (26.2%) ALS-patients elevated anti-ganglioside antibodies could be detected: Taking all subspecific antibodies together, IgG antibodies were found in 9/84 (10.7%) and IgM in 15/84 (17.9%) patients. There was no correlation between age, gender, site of onset or survival and anti-ganglioside-positive/-negative titres in ALS-patients. No statistically significant difference in the frequency of anti-ganglioside antibodies compared to the group of healthy blood donors was found.

CONCLUSION

Even with this more comprehensive approach, anti-ganglioside antibody frequencies and patterns in our ALS cohort closely resembled the values measured in healthy controls. In accordance with other studies, we did not observe any association of a distinct ALS phenotype with elevated anti-ganglioside antibodies or an impact on survival.

Clinical phenotype of patients with neuropathy associated with monoclonal gammopathy: a comparative study and a review of the literature

The objective of this study was to investigate if the clinical and electrophysiological phenotype of patients with polyneuropathy associated with IgM monoclonal gammopathy (IgM-PNP) is related to the presence of antibodies against gangliosides or myelin-associated glycoprotein (MAG). We compared clinical and nerve conduction study (NCS) characteristics of 11 IgM-PNP patients with antibodies against asialo-GM1 or gangliosides (GM1, GD1a, GD1b, GM2 or GQ1b) to 11 consecutive IgM-PNP patients with anti-MAG neuropathy and to 9 IgM-PNP patients without antibodies against either MAG or gangliosides. Patients with anti-ganglioside antibodies could not be differentiated from those with anti-MAG antibodies based on clinical characteristics. However, within the group of anti-ganglioside antibody positive patients, antibodies against GD1b and GQ1b were associated with a purely sensory neuropathy (p = 0.002), while asymmetric weakness with symmetric sensory loss was associated with anti-asialo-GM1 antibodies. In conclusion, polyneuropathy associated with IgM monoclonal gammopathy and anti-ganglioside antibodies clinically resembles anti-MAG neuropathy. Pure sensory neuropathy and marked asymmetry may suggest the presence of anti-ganglioside rather than anti-MAG antibodies.

Paraproteinemic neuropathies

The term paraproteinemic neuropathy refers to a heterogeneous group of neuropathies, which share the common feature of a homogeneous immunoglobulin in the serum. The presence of a monoclonal gammopathy indicates an underlying clonal B-cell expansion, which may appear in the context of a lymphoproliferative disorder. If a neoplastic origin of the gammopathy is identified, the treatment should be targeted to the neoplasm. In most patients, however, the monoclonal gammopathy is not associated with malignant haematological disorders, and is defined as monoclonal gammopathy of undetermined significance.

Non-anti-MAG DADS neuropathy as a variant of CIDP: clinical, electrophysiological, laboratory features and response to treatment in 10 cases

BACKGROUND AND PURPOSE

Some patients within the spectrum of chronic inflammatory demyelinating polyradiculoneuropathies (CIDP) have distal acquired demyelinating symmetric (DADS) neuropathy, usually associated with anti-myelin-associated-glycoprotein (MAG) IgM monoclonal gammopathy. The aim of this retrospective study was to investigate patients with DADS neuropathy without anti-MAG antibodies, and study their response to immunotherapy.

METHODS

Patients were selected on the basis of (i) 'Definite CIDP' according to the EFNS/PNS Guideline criteria, (ii) The presence of disproportionately prolonged motor latencies resulting in a terminal latency index (TLI) ≤ 0.25 in at least two motor nerves and (iii) The absence of anti-MAG antibodies on ELISA. Response to immunotherapy was defined as persistent improvement by at least one point on the INCAT disability score.

RESULTS

Data from 146 CIDP patients were analysed, and 10 patients were included. Six had clinically pure sensory neuropathy, and four had sensorimotor neuropathy. Ataxia was present in nine patients, generalized areflexia in seven and postural tremor in two. Five of the 10 patients had abnormal sensory potentials only in the upper limbs. An associated condition was found in nine patients: two chronic lymphocytic leukaemias, four IgG monoclonal gammopathies (one associated with non-Hodgkin's lymphoma) and two IgM monoclonal gammopathies of unknown significance. Patients were mostly improved with intravenous immunoglobulin (IVIg), corticosteroids, plasma exchanges, or a combination thereof.

CONCLUSION

DADS neuropathy without anti-MAG antibodies is more likely to be considered a variant of CIDP. In addition, such patients should be systematically investigated for an associated haematological or immunological condition.

How useful are anti-neural IgM antibodies in the diagnosis of chronic immune-mediated neuropathies?

Antibodies against several neural antigens have been associated with different chronic immune-mediated neuropathies but their practical clinical relevance remains unclear. To determine the possible diagnostic usefulness of these antibodies we reviewed the clinical correlate of IgM antibodies to the myelin-associated glycoprotein (MAG), sulfatide, the gangliosides GM1, GM2, GD1a and GD1b in 539 consecutive patients examined for neuropathy or related diseases in our Neuropathy Clinics and tested for these antibodies in our laboratory since 1985. 302 patients (56%) had an established diagnosis of definite or possible chronic immune-mediated neuropathy while 237 had a neuropathy of non-immune-mediated origin or of unknown aetiology or a closely related disease. Antibodies to one or more antigen were more frequent (chi(2)=63.32; p<0.00001) in patients with chronic immune-mediated neuropathy (37.7%) than with other neuropathy or related diseases (7.2%) and their presence was associated in 87% of the patients with an immune-mediated neuropathy, incrementing by 31% the probability of having this form. Testing for MAG permitted to identify 24.8% of patients with an immune-mediated neuropathy, GM1 an additional 9.9%, while GM2, GD1b, GD1a and sulfatide altogether an additional 3% of the patients. Concerning clinical correlations, all 75 patients with anti-MAG IgM had neuropathy and IgM monoclonal gammopathy (PN+IgM) with a positive predictive value for this neuropathy of 100%. A similarly high predictive value for neuropathy (91.4%) was observed among 269 patients with IgM monoclonal gammopathy including 103 patients without neuropathy. Anti-sulfatide IgM, though rare, were also significantly and constantly associated with PN+IgM and permitted to identify few patients not bearing anti-MAG IgM. Anti-GM1 IgM were significantly associated with multifocal motor neuropathy (MMN) (29.2%) but where also found in a few patients with other immune or non-immune neuropathies or related diseases with a positive predictive value for MMN of 25.5%. Anti-GM2 IgM were also significantly associated with MMN and increased the sensitivity (36.2%) for MMN obtained with anti-GM1 IgM only, without affecting its specificity and positive predictive value. Anti-GD1a, GD1b, though not significantly more frequent in patients with immune-mediated neuropathy, were associated in 80 to 100% of patients with these neuropathies. In conclusion anti-neural IgM antibodies may help in identifying patients with a chronic immune-mediated neuropathy, even if only anti-MAG and anti-sulfatide IgM appear to be strictly associated with a definite clinical syndrome.

Neuropathie ataxiante associée à des anticorps anti-gangliosides disialylés : description de nouvelles formes cliniques et biologiques

INTRODUCTION

Polyneuropathies associated with IgM monoclonal gammopathy were recently recognized. Antibodies can react with glycoproteins such as myelin associated glycoprotein (MAG), or gangliosides containing one sialosyl epitope such as GM1 or several sialosyl epitopes (polysialyted gangliosides) including GD2, GD3, GT1b, GT1a, GQ1b.

METHODS

We report on three patients presenting oculomotor dysfunction, chronic sensitive ataxic polyneuropathy, high sedimentation rate, IgM monoclonal paraprotein of unknown signification and antidisialosyl IgM antibodies and for two of them cold agglutinins. Such features have been previously described under the acronym "CANOMAD" (chronic ataxic neuropathy with ophthalmoplegia, M protein, agglutination and disialosyl antibodies).

RESULTS

One of the patients presents extramembranous glomerulopathy and severe motor disability associated with this syndrome. The pathophysiology of the glomerulopathy seems to be linked with the polyneuropathy. Patients were treated either by intravenous immunoglobulin, corticosteroids or cyclophosphamid. Response to treatment differs in the three cases and there is currently no consensus.

CONCLUSION

Our study demonstrates that spectrum of polyneuropathy associated with monoclonal polyneuropathy may be larger than originally described.

Intravenous immunoglobulin therapy in multifocal motor neuropathy: a double-blind, placebo-controlled study

We conducted a double-blind, placebo-controlled, study of 19 patients fulfilling eligibility criteria for multifocal motor neuropathy with persistent conduction block. They were enrolled and divided into two groups: those who had never been treated previously with intravenous immunoglobulins (IVIg) (Group 1: 10 patients) and those who presented recurrent symptoms after previously successful treatment with IVIg (Group 2: nine patients). They were randomized prospectively to receive either IVIg or placebo at a dose of 500 mg/kg/day for 5 consecutive days, once a month for 3 months. At month 4, patients found to be responders remained on the same treatment for the 3 following months, while non-responders were switched to the alternative study drug for the 3 following months. Clinical assessment was conducted with the MRC score in 28 muscles and a self-evaluation scale (five daily motor activities scored from 0 to 5). In Group 1, nine patients completed the study, of whom initially four received IVIg and five placebo; four patients responded to IVIg (two at months 4 and 7, and a further two at month 7 after switching treatment at month 4), two patients responded to placebo at months 4 and 7, and three patients did not respond to either treatment. In Group 2, nine patients completed the study. Five patients first received IVIg and all responded at months 4 and 7. Four patients first received placebo and none responded at month 4; all were then switched to IVIg and three responded at month 7. When the 18 patients were considered together, seven out of the nine patients who received IVIg first were responders at month 4, compared with two of the nine patients who received placebo first, a difference that was statistically significant (P = 0.03). On the other hand, there was no significant difference in MRC score but a significant difference in the self-evaluation score, at month 4, between IVIg patients and placebo patients. Electrophysiological studies did not show significant differences at month 4 in motor parameters between IVIg patients and placebo patients. IgM anti-GM1 titres did not change significantly in patients treated with IVIg compared with those who received placebo, between baseline, month 4 and month 7. However, of five patients who had significantly high anti-GM1 titres (>3200) at baseline, four responded to IVIg. This trial confirms that IVIg is a promising therapeutic option for multifocal motor neuropathy.

Clinicopathological study of an autopsy case with sensory-dominant polyradiculoneuropathy with antiganglioside antibodies

A previously reported patient presenting sensory-dominant neuropathy with antiganglioside antibodies, bound preferentially to polysialogangliosides including GD1b, was autopsied. While axonal degeneration was predominant in the sural nerve, many demyelinated fibers were present in the spinal roots. Dorsal roots had undergone significant damage. These pathological findings were well correlated with the electrophysiological results showing decreased F-wave conduction velocities and conduction blocks in motor nerves and decreased or absent sensory action potentials in sensory nerves, with distribution of GD1b in nerve tissues such as dorsal root ganglia and paranodal myelin in the ventral and dorsal roots.

Antiglycolipid antibodies in motor neuropathies

In peripheral neuropathies with monoclonal gammopathy, mainly IgM, it appears clear from clinical, electrophysiological, and experimental data, that the target glycolipid or glycolipid epitope for the IgM is related to the type of neuropathy--purely sensory, predominantly sensory, or uniquely motor. Investigations have focused on chronic peripheral neuropathies associated with polyclonal IgM reactivity to glycolipids. Although IgM anti-GM1 antibodies are present in normal controls, there is a subgroup of motor neuropathies with high titer anti-GM1 antibodies, mainly multifocal neuropathies with conduction blocks (MMNCB). Another subgroup of MMNCB may include IgM anti-SGPG antibodies that do not cross-react with MAG. The importance of the fine structure of the epitope has to be considered in view of the pathogenicity of the antibody. It may bear consequences on its binding properties on the neuronal surfaces and on its biological implications.

The role of antiglycolipid antibodies in neurological disorders

Glycolipids have been shown to be antigens for circulating antibodies in autoimmune processes affecting the nervous system like neuropathy associated with IgM paraproteinemia, Guillain Barré syndrome (GBS), multifocal neuropathy, and variants thereof. The antibody titers, the Ig-classes, and the antibody specificity vary between studies and disease groups. The immunogens are in general unknown. However, GBS is often associated with an infection with Campylobacter jejuni, which expresses a lipopolysaccharide structure similar to the carbohydrate epitopes in sialic acid containing glycolipids and gangliosides and thus a potential primary antigen for antiganglioside antibodies. The antiglycolipid specificity will most likely reflect the primary antigen carbohydrate epitopes, which also determine the target cell or tissue structure and the pathology. These factors might add to the inconsistent results obtained and that have led to the question: Are antiglycolipid antibodies of any clinical significance?

Peripheral neuropathy associated with IgM monoclonal gammopathy: correlations between M-protein antibody activity and clinical/electrophysiological features in 40 cases

Forty cases of polyneuropathy associated with IgM monoclonal gammopathy were retrospectively studied to investigate the relevance of clinical and electrophysiological features to M-protein antibody activity. There were 26 men and 14 women; mean age was 65 +/- 11.7 years at the time of the study. Thirty-nine patients had a symmetrical polyneuropathy, of whom 13 had a predominantly sensory and 17 a purely sensory neuropathy (i.e., 30 sensory neuropathies). The remaining patient had a multifocal mononeuropathy. Electrophysiological studies allowed the polyneuropathies to be classified as demyelinating in 33 cases (82.5%) and axonal in 6 cases. Antibody studies disclosed anti-MAG antibodies in 65% and anti-SGPG antibodies in 82.5% of patients. Anti-MAG antibodies were associated with only demyelinating polyneuropathies. Anti-SGPG antibodies were found in 91% of demyelinating polyneuropathies and 50% of axonopathies. In addition, anti-MAG/SGPG antibody activity was significantly correlated with the subgroup of sensory neuropathies (P < 0.01). Last, antisulfatide antibodies were found at significant titers in 18 cases, and their presence was significantly correlated with anti-MAG/SGPG antibody activity, but not with some clinical/electrophysiological features.

Prominent sensory ataxia in Guillain-Barré syndrome associated with IgG anti-GD1b antibody

Sensitization with GD1b has been shown to cause sensory neuropathy in rabbit. A patient with chronic sensory-dominant polyneuropathy who had IgM antibody specifically to GD1b has been reported previously. This report describes the first patient with acute demyelinating polyneuropathy with prominent sensory symptoms who had a high titer of serum IgG anti-GD1b antibody. The serum reacted with neither GM1 nor with other b-series gangliosides (GD2, GD3, GT1b and GQ1b). Improvement in symptoms was coincident with decrease in IgG anti-GD1b antibody titer after plasmapheresis. This case supports the experimental results in rabbit suggesting that anti-GD1b antibody functions in the development of sensory ataxia.

A monoclonal antibody that recognizes ganglioside GD1b in the rat central nervous system

A monoclonal antibody (MAb), generated by immunizing BALB/c mice with homogenized bovine retinal tissue, was specific to ganglioside GD1b incorporated into liposome membranes. The antibody (MAb-5G6), classified as IgM, immunostained intensely the perikaryon and processes of motoneurons in the cranial motor nuclei and spinal cord. Spinal and trigeminal ganglion cells were also immunopositive to the MAb. Some fiber tract systems, such as the spinal and mesencephalic trigeminal tracts, the solitary tract and the posterior funiculus, were also immunoreactive to the MAb. These findings suggest that MAb-5G6 labeled specifically neurons with axons extending outside of the central nervous system as a peripheral nerve. The immunoreactive substances were visualized under electron microscopy just beneath the postsynaptic membrane and just inside the plasmalemma of the thick dendrites. No axon terminal was immunolabeled by the MAb. In the rat embryos, immunoreactivity to MAb-5G6 was found in the dorsal and ventral root fibers on the 15th embryonic day (E15). However, cell bodies of the spinal ganglion cells and motoneurons were immunostained by MAb-5G6 at a later stage (E20). The ventral commissure fibers in the floor plate of the spinal cord were transiently immunolabeled during E13-15.

Plasma exchange and chlorambucil in polyneuropathy associated with monoclonal IgM gammopathy. IgM-associated Polyneuropathy Study Group

The study compared chlorambucil alone with chlorambucil in combination with plasma exchange in patients with polyneuropathy associated with monoclonal IgM. Forty four patients were prospectively randomly assigned, in a comparative open trial, to receive either 0.1 mg/kg/day chlorambucil orally, for 12 months or chlorambucil associated with 15 courses of plasma exchange, during the first four months of treatment. They were evaluated by a neuropathy disability score and nerve conduction studies. No difference was found between the two treatment groups. The average neuropathy disability score improved by 2.1 points from baseline (21.0 to 18.9) in the chlorambucil group and by 1.8 points (20.4 to 18.6) in the chlorambucil + plasma exchange group (P = 0.70). The mean motor nerve conduction velocity decreased from 20.0 to 18.2 m/s in the chlorambucil group and increased from 20.5 to 22.5 m/s in the chlorambucil + plasma exchange group (P = 0.51). A slight improvement of the sensory component of the neuropathy disability score (from 10.5 to 8.3) was noted in both groups (P = 0.01). At the end of the study and according to self evaluation, 15 patients--eight from the chlorambucil group and seven from the chlorambucil + plasma exchange group--reported clinical improvement, whereas 15--eight from the chlorambucil group and seven from the chlorambucil + plasma exchange group--reported clinical worsening. Neuropathy remained stable in the others. Thus plasma exchange seemed to confer no additional benefit in the treatment of polyneuropathy associated with monoclonal IgM.

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.

Anti-sulfoglucuronyl paragloboside IgM antibodies in amyotrophic lateral sclerosis

We report here our results on IgM anti-sulfated glucuronyl paragloboside (SGPG) antibodies in sera from patients with amyotrophic lateral sclerosis (ALS). Studies by enzyme linked immunosorbent assay on 72 ALS sera showed IgM polyclonal reactivity towards SGPG in 25 cases. The titer was high in 16 cases. Thin-layer chromatography immuno-overlay showed that reactivity with SGPG was associated to reactivity towards GM1 in five cases and to GM1 and GD1b in one case. Anti-SGPG reactivity was not found in controls and in multifocal motor neuropathy with conduction blocks, in contrast to anti-GM1 antibodies. The presence of anti-SGPG antibodies in ALS patients sera raise again the question of autoimmunity in this pathology.

Human immunoglobulin treatment of multifocal motor neuropathy and polyneuropathy associated with monoclonal gammopathy

Intravenous human immune globulin (IVIg) has been proposed for the treatment of various peripheral neuropathies that are considered to be immunemediated. The results are reported of an open trial conducted in multifocal motor neuropathy and polyneuropathy associated with monoclonal gammopathy. Six cases with multifocal motor neuropathy, selected on clinical and electrophysiological criteria (four of six patients also had significantly high anti-GM1 titres), received IVIg monthly, at doses varying from 1.6 to 2.5 mg/kg, over three to 13 months. The initial response to treatment was dramatic in 3/6 cases (with improvement of at least two grades on the MRC scale in the five more severely affected muscles). The final evaluation showed a good result in 4/6 cases, but the conduction blocks were not significantly reduced. In 13 other cases with polyneuropathy associated with IgM monoclonal gammopathy of unknown significance, IVIg was of benefit, with improvement of at least one grade on the Prineas score, in 4/7 cases previously treated with immunosuppression and 2/3 cases not treated before IVIg. In the last group of four patients with polyneuropathy and IgG monoclonal gammopathy, IVIg was followed by clinical improvement in the two cases with a chronic demyelinating polyneuropathy.

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.

Anti-B-series ganglioside-recognizing autoantibodies in an acute sensory neuropathy patient cause cell death of rat dorsal root ganglion neurons

To examine the cytotoxicity of a patient's serum with an acute relapsing sensory neuropathy syndrome, dorsal root ganglion neurons from young adult rats were cultured in the presence of the patient's serum which had an extremely higher-titer monoclonal IgM antibody recognizing B-series gangliosides, GD2, GD1b, GT1b and GQ1b. By the addition of the inactivated patient's serum, the relatively larger cells died after undergoing of metamorphosis during several hours of culture, whilst the smaller cells survived. The IgM fraction isolated from the patient's serum showed similar cytotoxicity towards the neurons as the inactivated whole serum. No cytotoxicity was observed with the IgM fraction-containing medium after it had been absorbed with ganglioside GD1b. The results suggested that the anti-B-series ganglioside-directed antibody is the causal agent for the human neurologic disease.