The myelin-associated glycoprotein (MAG) is a transmembrane protein with a molecular weight of 100 kDa which exists in two isoforms (L-MAG-and S-MAG).
MAG represents approximately 0.1 – 1 % of the total myelin proteins of the peripheral and central nervous system.

Anti-MAG autoantibodies are detected in 50 % of patients with peripheral demyelinating neuropathies associated with a monoclonal IgM-gammopathy (Waldenström’s macroglobulinemia and MGUS = monoclonal gammopathie of undetermined significance). The detection of anti-MAG autoantibodies in these diseases is of diagnostic relevance.

The autoantibodies are directed against epitopes of the carbohydrate part of MAG. One of these epitopes (HNK1) is also expressed on the glycolipids SGPG and SGLPG.

There seems to be a correlation between the anti-MAG autoantibody titer and the grade of demyelinisation.

Anti-MAG autoantibodies, without diagnostic meaning, are rarely found in patients with multiple sclerosis, Guillain-Barré-Syndrom, chronic neuropathies and Myasthenia gravis.

Procedure (Short Description):

• Preabsorb serum samples according to the instruction for use.
  Cover one strip with the ready to use positive control.
  Cover the other strips with 2 ml dilution buffer.
  Add 20 µl of the preabsorbed serum sample and mix carefully.
  

• Incubate for 60 minutes at room temperature on a rocking table.
  

• Wash three times for three minutes with diluted wash buffer.
  

• Add 2 ml alkaline phosphatase IgM conjugate, ready to use, per strip.
  

• Incubate for 60 minutes at room temperature on a rocking table.
  

• Wash three times for three minutes with diluted wash buffer.
  

• Add 2 ml ready to use substrate-solution per strip!
  

• Incubate for 10 minutes at room temperature until the bands become clearly visible. See control scan for comparison.
  

• Transfer the strips to distilled water to stop the reaction. Put the strips onto filter paper and let them dry. Store the strips in the dark.