IgM in a human neuropathy related to paraproteinemia binds to a carbohydrate determinant in the myelin-associated glycoprotein and to a ganglioside.

The IgM in three patients with paraproteinemia and peripheral neuropathy was shown to bind to human myelin-associated glycoprotein (MAG) that had been purified to homogeneity by gel filtration on Sepharose CL-6B. The antigenic determinant reacting with the IgM from all three patients was in the carbohydrate part of the MAG molecule. In addition, the IgM from the same three patients bound to a single ganglioside of human sciatic nerve. The results indicate that the IgM paraproteins in these patients react with a carbohydrate determinant that is shared between MAG and a peripheral nerve ganglioside.