Antibodies to myelin-associated glycoprotein are found in cerebrospinal fluid in polyneuropathy associated with monoclonal serum IgM

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.

Severe cranial nerve involvement in a patient with monoclonal anti-MAG/SGPG IgM antibody and localized hard palate amyloidosis

We report a patient with severe cranial polyneuropathy as well as sensory limb neuropathy. Biclonal serum IgM-kappa/IgM-lambda gammopathy was found and serum anti-myelin-associated glycoprotein (MAG)/sulfoglucuronyl paragloboside (SGPG) IgM antibody was also detected. Immunofluorescence analysis of a sural nerve biopsy specimen revealed binding of IgM and lambda-light chain on myelin sheaths. No amyloid deposition was detected in biopsied tissues except for the hard palate, suggesting that the amyloidosis was of the localized type and had no relation to the pathogenesis of cranial neuropathy. Our observations indicate that the anti-MAG/SGPG IgM antibody may be responsible for this patient's cranial polyneuropathy, which is a rare manifestation in anti-MAG/SGPG-associated neuropathy.

Multiple MAG peptides are recognized by circulating T and B lymphocytes in polyneuropathy and multiple sclerosis

Abnormal immune responses to myelin associated glycoprotein (MAG), a component of myelin of the central and peripheral nervous system, have been suggested to play a role in the pathogenesis of multiple sclerosis (MS) and certain types of inflammatory polyneuropathy. To identify possible immunodominant MAG peptides in neuroinflammation, we examined T and B cell responses to five selected synthetic MAG peptides and myelin proteins in 21 patients with non-inflammatory polyneuropathy, 26 patients with MS, 10 optic neuritis patients and 17 healthy subjects. Enzyme-linked immunosorbent spot-forming cell assays were adopted, allowing the detection and enumeration of individual antigen responsive T and B cells in body fluids. Patients with polyneuropathy as well as those with MS had elevated levels of T and B cells recognizing MAG and its peptides. Any of the five MAG peptides under study functioned as immunodominant T and/or B cell epitope in individual subjects. None of the MAG peptides elicited a specific disease-associated T or B cell response. The enhanced T and B cell response to myelin components like MAG may play some role in initiation and/or progression of these diseases, but they could also represent secondary responses associated with myelin damage and indicate tolerization rather than autoaggressive immunity.

Myelin protein P0-specific IgM producing monoclonal B cell lines were established from polyneuropathy patients with monoclonal gammopathy of undetermined significance (MGUS)

Monoclonal expansion of B cells and plasma cells, producing antibodies against 'self' molecules, can be found not only in different autoimmune diseases, such as peripheral neuropathy (PN), but also in malignancies, such as Waldenström's macroglobulinaemia and B-type of chronic lymphocytic leukaemia (B-CLL), as well as in precancerous conditions including monoclonal gammopathy of undetermined significance (MGUS). About 50% of patients with PN-MGUS have serum antibodies against peripheral nerve myelin, but the specific role of these antibodies remains uncertain. The aims of the study were to establish, and characterize, myelin-specific B cell clones from peripheral blood of patients with PN-MGUS, by selection of cells bearing specific membrane Ig-receptors for myelin protein P0, using beads coated with P0. P0-coated magnetic beads were used for selection of cells, which subsequently were transformed by Epstein--Barr virus. The specificity of secreted antibodies was tested by ELISA. Two of the clones producing anti-P0 antibodies were selected and expanded. The magnetic selection procedure was repeated and new clones established. The cells were CD5+ positive, although the expression declined in vitro over time. The anti-P0 antibodies were of IgM-lambda type. The antibodies belonged to the VH3 gene family with presence of somatic mutations. The IgM reacted with P0 and myelin-associated glycoprotein (MAG), and showed no evidence for polyreactivity, in contrast to other IgM CD5+ clones included in the study as controls. The expanded clones expressed CD80 and HLA-DR, which is compatible with properties of antigen-presenting cells. The immunomagnetic selection technique was successfully used for isolation of antimyelin protein P0-specific clones. The cell lines may provide useful tools in studies of monoclonal gammopathies, leukaemia, and autoimmune diseases, including aspects of antigen-presentation by these cells followed by T cell activation.

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)

Abnormalities in T-lymphocyte populations in blood from patients with demyelinating polyneuropathy associated with monoclonal gammopathy

Patients with monoclonal gammopathy secrete monoclonal antibodies (M-component), that in some patients are associated with polyneuropathy. The M-component has been shown to react with peripheral nerve myelin in some of these patients. However, it is not known whether the M-component secreting B-cells are autonomous or subject to regulation by T-cells or if other cellular abnormalities may occur. In order to define circulating lymphocyte subpopulations, flow cytometry was done on blood samples from patients with monoclonal gammopathy and demyelinating polyneuropathy (n = 13) and patients with monoclonal gammopathy without polyneuropathy (n = 11), and were compared to healthy controls. Significantly increased proportions of primed T-helper (CD4+) cells, i.e. those expressing helper/inducer function (CD29+ CD4+), providing help for antibody secretion, as well as decreased proportions of naive, unprimed suppressor/inducer (CD45RA+ CD4+) T-helper cells were found in patients with M-component associated polyneuropathy. Within the T-cytotoxic/suppressor population (CD8+) we found an increased proportion of killer/effector (S6F1+ CD8+) cells and a decreased proportion of suppressor/effector (S6F1- CD8+) cells in patients with monoclonal gammopathy and polyneuropathy. Similar findings were found in monoclonal gammopathy patients without polyneuropathy, although the deviations in general were less pronounced and did not reach statistical significance compared to the controls. The proportion of natural killer (NK) cells (CD56+) was markedly decreased in all patients with monoclonal gammopathy. In the whole group of patients with monoclonal gammopathy, we found clear proportions of interleukin-2 receptor (CD25+) expressing lymphocytes, indicating the presence of activated T-cells. No clear correlation between abberations in T-cell subtypes and clinical severity of the demyelinating polyneuropathy or titres of anti-PNM antibodies was found.(ABSTRACT TRUNCATED AT 250 WORDS)

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

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

Clinical, neurophysiological and immunological evidence of polyneuropathy in patients with monoclonal gammopathies

In this study we estimated the prevalence of polyneuropathy (PN) in patients with monoclonal gammopathies. 31 patients with monoclonal gammopathies (19 with monoclonal gammopathy of uncertain significance (MGUS), 10 with multiple myeloma (MM), and 2 with Waldenström's macroglobulinemia), were studied by clinical and neurophysiological examination, blood tests to exclude other causes of PN, ELISA assays to detect antibodies to peripheral nerve myelin (PNM), and antibodies to myelin associated glycoprotein (MAG). 11 of 31 patients (36%) had a clinical PN, 3 (10%) had a probable PN (signs but no symptoms), and 4 (13%) had a subclinical PN (only neurophysiological signs of PN). Thus, in total 18 patients (58%) had some form of PN, in contrast to an age-matched control group (n = 33) where only 2 persons (6%) had some form of PN; 1 had a probable PN and 1 had a subclinical PN. 3 patients had anti-PNM and anti-MAG antibodies of IgM isotype, all 3 patients showing a demyelinating PN. The remaining patients with PN had a mild or moderate distal PN. One patient had a myelopathy and 1 had amyotrophic lateral sclerosis (ALS). IgM isotype of the M-protein was associated with a high risk of clinical PN (5 out of 6 (83%)), in contrast to IgG (5 out of 18 (28%)) and IgA (1 out of 6 (17%)). We conclude that PN is a common finding in patients with monoclonal gammopathies, but only some of them are of the demyelinating type and associated with antibodies to PNM or MAG.

Peripheral neuropathies associated with monoclonal proteins

Peripheral neuropathies associated with monoclonal proteins have received considerable attention as a clinically important group of chronic late-onset neuropathies. When a monoclonal protein is found in patients with peripheral neuropathy of unknown cause, as occurs in 10% of such cases, usually no associated disease is discovered; hence MGUS. Less often, disorders such as multiple myeloma, AL amyloidosis, Waldenström's macroglobulinemia, osteosclerotic myeloma, and lymphoma are found. Demyelinating neuropathies associated with MGUS of all classes, but particularly IgM, Waldenström's macroglobulinemia, and osteosclerotic myeloma typically follow an indolently progressive course, and frequently respond to treatments aimed at interfering with putative underlying immune mechanisms. By contrast, axonal neuropathies associated with MGUS, multiple myeloma, and AL amyloidosis have generally shown no response to therapy. Recently, IgM monoclonal and polyclonal antibodies directed against human peripheral nerve antigens including MAG and various glycolipids such as GM1 ganglioside have been found in patients with specific neuropathy syndromes. Anti-MAG antibodies occur in predominantly sensory demyelinating neuropathies, whereas elevated titers of anti-GM1 ganglioside antibodies are associated with lower motor neuron syndromes with multifocal motor conduction block. Although the evidence for autoimmune mechanisms in some monoclonal protein-associated neuropathies is mounting, a causal connection between monoclonal proteins and these neurologic syndromes has yet to be established.