Human monoclonal IgM autoantibodies with restricted antigenic specificity for myelin express unrelated idiotypes

Idiotype-specific polyclonal antisera were prepared against myelin-binding human IgM paraproteins with specificity for the myelin-associated glycoprotein (MAG). Eight anti-idiotypic sera (6 against one monoclonal IgM and 2 against another) were tested by gel precipitation, immunoradiometric and ELISA assays for binding to the myelin-binding IgM paraproteins from 12 patients with demyelinating peripheral neuropathy. Anti-idiotypic antibodies bound only to the MAG-specific IgM used for immunization; there was no evidence of idiotypic cross-reactivity between the different IgM paraproteins.