Myelin Associated Glycoproteins (MAG) Antibodies

Neuropathies associated with anti-MAG are often slowly progressive with evidence of demyelination and a variable degree of axonal loss associated with gait ataxia. 50% of all peripheral neuropathy cases with IgM paraproteinemia possess anti-MAG antibodies. Detection of anti-MAG autoantibodies is useful for the clinician, as it suggests active demyelination in a peripheral neuropathy.

Immunofluorescence is a sensitive method for the screening and detection of anti-nerve myelin associated proteins and ganglioside autoantibodies.

Specimens found positive by immunofluorescence can be confirmed using the Western Blot method.

Neuronal Antibodies

The following auto-antibodies are found in paraneoplastic syndromes:

1. anti-Hu, type I anti-neuronal nuclear antibody (ANNA-1), is associated with small cell lung cancer resulting in paraneoplastic encephalomyelitis (PE).
2. anti-Yo, anti-purkinje cell antibodies (PCA-1), is associated with ovarian and breast carcinomas resulting in paraneoplastic cerebellar degeneration (PCD).
3. anti-Ri, type II anti-neuronal nuclear antibody (ANNA-2), is associated with neuroblastoma (children) and fallopian or breast cancer (adults) resulting in paraneoplasticopsoclonus myoclonus ataxia (POMA).

These markers help in discriminating between true paraneoplastic disorders and other inflammatory disorders of the nervous system that mimic a paraneoplastic syndrome. IFA provides a sensitive method of detecting these auto-antibodies. anti-Hu/anti-Ri autoantibodies, which characteristically stain the granular cell nucleus, are easily distinguished from the Purkinjee cell cytoplasm staining anti-Yo antibodies. Specimens found positive by IFA can be confirmed using the Western Blot method.

Ganglioside Antibodies

Patients exhibiting neuropathies elicit antibodies to gangliosides, acidic glycosphingolipids localized in the outer layer of plasma membranes. These antibodies may be directed against GM1, Asialo GM1, GD1a, GD1b, GQ1b, sulfatides and/or galactocerebroside.

Ribosomal P & Ribonucleic Acid (RNA) Antibodies

In patients with psychotic SLE, a group of autoantibodies is targeted against the ribosomal phosphoproteins, called P0 (38kD), P1 (19kD) and P2 (17kD).

Preceding the onset of psychotic episodes in patients, a selective elevation of anti-Ribosomal P antibodies has been observed.