Anti-glycolipid antibodies in the diagnosis of autoimmune neuropathies

Recent years have seen major progress in our understanding of the clinical pathophysiology of autoimmune neuropathies particularly with the identification and analysis of antibodies to gangliosides and related glycolipids in the serum of patients. Anti-glycolipid antibodies react with epitopes on the carbohydrate region of glycolipid molecules and can be routinely measured by standard immunoassays. In multifocal motor neuropathy, IgM anti-GM1 antibodies that cross react with GD1b and asialo-GM1 are detectable in around 50p. 100 of cases. This condition may clinically resemble certain forms of lower motor neurone disease. IgM anti-GD1b antibodies are found in IgM paraproteinaemic neuropathy characterised by profound sensory ataxia. In the anti-myelin associated glycoprotein (anti-MAG) IgM paraproteinaemic neuropathy, antibodies also react with the acidic glycolipids, sulphated glucuronyl paragloboside and its higher lactosaminyl homologue (SGPG and SGPLG). Thus a variety of chronic syndromes can be defined by their anti-glycolipid antibody profile. In Guillain-Barré syndrome, anti-GM1, GM1b, GD1a and GalNAc-GD1a antibodies are found in patients with acute motor axonal neuropathy (AMAN) and anti-GQ1b IgG antibodies are a very sensitive and specific marker for the Miller Fisher syndrome. Many other anti-glycolipid antibodies are being increasingly identified in other neuropathy subtypes. The article will summarise existing clinical and serological information in this field.     

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

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

Identification and use of biomarkers in Gaucher disease and other lysosomal storage diseases

The value of biomarkers in the clinical management of lysosomal storage diseases is best illustrated by the present use of plasma chitotriosidase levels in the diagnosis and monitoring of Gaucher disease. The enzyme chitotriosidase is specifically produced and secreted by the pathological storage macrophages (Gaucher cells). Plasma chitotriosidase levels are elevated on average 1000-fold in symptomatic patients with Gaucher disease and reflect the body burden on storage cells. Changes in plasma chitotriosidase reflect changes in clinical symptoms. Monitoring of plasma chitotriosidase levels is nowadays commonly used in decision making regarding initiation and optimization of costly therapeutic interventions (enzyme replacement therapy or substrate reduction therapy). A novel substrate has been developed that further facilitates the measurement of chitotriosidase in plasma samples. Moreover, an alternative Gaucher-cell marker, CCL18, has been very recently identified and can also be employed to monitor the disease, particularly in those patients lacking chitotriosidase due to a genetic mutation. There is a need for comparable surrogate markers for other lysosomal storage diseases and the search for such molecules is an area of intense investigation.
Conclusion: The use of biomarkers can provide valuable insight into the molecular pathogenesis of LSDs, such as Gaucher disease and Fabry disease.     

Antibodies to tumor necrosis factor alpha prevent increases in cell replication in liver due to the potent peroxisome proliferator, WY- 14,643

Several structurally dissimilar hypolipidemic drugs, plasticizers and halogenated hydrocarbons induce peroxisomes in hepatocytes, and cause hepatocellular adenoma and carcinoma in rats and mice. The mechanism by which these agents act is unknown, although recent studies have suggested a link between increased cell proliferation and hepatic cancer caused by peroxisome proliferators. Here, we demonstrate that neutralizing antibodies to tumor necrosis factor alpha (TNF alpha) block increases in protein kinase C and cell proliferation due to [4- chloro-6-(2,3-xylidino)-2-pyrimidinylthio]acetic acid (WY-14,643), a hypolipidemic drug and potent peroxisome proliferator that causes tumors. WY-14,643 moderately elevated the level of TNF alpha mRNA in the liver. TNF alpha was detected immunohistochemically exclusively in Kupffer cells. These results demonstrate that WY-14,643 acts as an indirect mitogen on hepatocytes via TNF alpha. We propose that the Kupffer cell, a major source of TNF alpha in the liver, is involved in the mechanism of the mitogenic effect of WY-14,643.      

Evaluation of attempted prevention of unexpected infant death in very high-risk infants by planned health care

Three hundred and ninety-six babies born in Sheffield between 1982 and 1990 identified as being at "very high risk" of unexpected infant death by means of a scoring system, received an intensive programme of health care including a case discussion between a paediatrician, the GP and the health visitor held in the family doctor's surgery, weekly visits from the health visitor and informal hospital admission. Significantly fewer sudden unexpected infant deaths occurred in this group than were expected by logistic regression anlysis or occurred in the best available control group with comparable scores ( p = 0.024). Problems in evaluation include identification of an adequate control population, ethical difficulties in introducing a controlled study when the programme is already perceived as effective, and the calculation of "expected death rates". The results of this study indicate that very energetic programmes of intervention may prevent some deaths in vulnerable infants.     

Gangliosides and bacterial toxins in Guillain-Barré syndrome

Autoimmune factors are strongly favoured as mediating Guillain-Barré syndrome (GBS); however, the precise mechanisms by which this occurs remain unknown. Microbial infections in a susceptible host resulting in an idiosyncratic immune response which cross-reacts with nerve constituents still remains the most plausible working hypothesis on which much current research is based. Considerable recent evidence indicates that this humoral immune response is at least in part directed to gangliosides. Interestingly, many bacterial toxins, including botulinum and tetanus neurotoxins, also bind to gangliosides and induce diseases with some similarities to GBS. This article discusses the evidence in favour of a pathogenic role for anti-ganglioside antibodies in GBS in the context of our knowledge of the biology of gangliosides and the factors that determine their immunogenicity.