Polyneuropathy with monoclonal gammopathy: glycolipids are frequently antigens for IgM paraproteins.

Immunoglobulins from patients with paraproteinemic polyneuropathy were screened for reactivity with nerve and brain glycolipids by ELISA and/or a thin-layer-chromatogram-overlay technique. The myelin-associated glycoprotein (MAG) has been shown to be an antigen in many neuropathy patients with IgM gammopathy, but this study focused on seven neuropathy patients in which the IgM paraproteins had been shown not to react with this glycoprotein. Five of these seven had IgM that reacted with components in the acidic glycolipid fraction of human sciatic nerve, and three of these IgMs also reacted with components in the acidic glycolipid fraction of human brain. Little or no reactivity with glycolipids was detected for two patients with neuropathy and IgG gammopathy or for two with neuropathy and IgA gammopathy. The results suggest that neuropathy-patient IgM paraproteins not reactive with MAG often react with acidic glycolipids and thus define a subset of paraproteinemic neuropathies. Since the IgM paraproteins that react with MAG also react with acidic glycolipids of nerve, glycolipid antigens appear to be quite common among the IgM paraproteinemic neuropathies.