Clonality of anti-GM1 IgM antibodies in multifocal motor neuropathy and the Guillain-Barré syndrome

Objective Multifocal motor neuropathy (MMN) and the Guillain-Barré syndrome (GBS) are immune-mediated motor neuropathies with antibodies against the ganglioside GM1. In GBS, these antibodies are induced by molecular mimicry, but in MMN their origin is elusive. Methods We compared the light-chain use of anti-GM1 IgM antibodies in serum from 42 patients with MMN and 23 patients with GBS by ELISA. Results Exclusive use of either κ or λ light chains was found in 38 (90%) patients with MMN and 9 (39%) with GBS (p<0.001). Conclusions Anti-GM1 IgM antibodies in most patients with MMN are produced by only a single or very limited number of B-cell clones, whereas in most patients with GBS, anti-GM1 IgM antibodies are most likely polyclonal.

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