Keywords
anti-MAG
human autoantibodies
autoimmune paraproteinemic neuropathies
How to Cite
Abstract
Frozen sera from 66 untreated patients with IgM-monoclonal gammopathy (IgM-MG) were studied to search for antigen specificity of the M-protein to myelin-associated glycoprotein (MAG) (anti-MAG-IgM) by ELISA. In 46 patients (70%), the M-protein reacted with MAG. Anti-MAG-IgM titers ranged between 5500 and 68000 BTU (reference value < 1000 BTU). The concentration of monoclonal IgM (mIgM) ranged from 499 to 2800 mg/dl (nephelometric quantitation). The sex ratio was M/F 2.7 and the mean age 51 ± 12 years old. The sera were previously identified as IgM-Kappa (53 patients) and IgM-Lambda (13 patients) by means of immunofixation electrophoresis. The correlation between the monoclonal IgM (mIgM) concentration and
anti-MAG-IgM titers was 0.84. According to the clinical records, 34 of 46 patients with peripheral neuropathy were mIgM-anti-MAG (+): sensory (74%) and sensorimotor (26%) pattern. Twenty patients with mIgM-anti- MAG (-) had sensorimotor peripheral neuropathy, exclusively. We found a strong association between IgMMG/ anti-MAG-IgM reactivity and peripheral neuropathy, predominantly sensory peripheral neuropathy. The higher prevalence of neuropathy in patients with IgM-MG might be related to the frequent reactivity of mIgM with the MAG antigen. Our results also suggest that the IgM paraproteins in neuropathy patients who are MAG(-) could react with other glycolipid antigens, and thus define a subset of autoimmune paraproteinemic
neuropathies. This might be relevant to better understand the pathogenic mechanisms occurring in these patients. Since the anti-MAG(+)IgM paraproteins could also react with other neural glycolipids, glycolipid antigens appear to be quite common among IgM paraproteinemic neuropathies. However, this requires further investigation.