Specificity of human IgM monoclonal antibodies from patients with peripheral neuropathy

Some patients with peripheral neuropathy and gammopathy have IgM monoclonal antibodies that react with the myelin-associated glycoprotein (MAG), some 20-26 kDa glycoproteins present only in the peripheral nervous system (PNS), and some acidic glycolipids that are also PNS-specific. This communication describes an investigation of 18 patients with IgM paraproteinemia and neuropathy to test for the presence of antibodies that react with each of these components. Eleven patients had IgM that reacted with MAG, and in all cases the IgM also reacted with the lower Mr glycoproteins and the acidic glycolipids that are specific for the PNS. With respect to the other 7 patients that did not react with MAG, in no instance did immune-staining of electroblots reveal the presence of reactivity with the 20-26 kDa glycoproteins of the PNS or with any other protein antigen in the PNS or central nervous system (CNS). However, these 7 patients fell into 3 categories with regard to reactivity with acidic glycolipids: three reacted with the acidic glycolipid fraction of both PNS and CNS tissue; two reacted with the acidic glycolipid fraction of the PNS but not the CNS; and two showed no reactivity with the acidic glycolipids from either PNS or CNS.