Anti-ganglioside complex IgM antibodies in multifocal motor neuropathy and chronic immune-mediated neuropathies

Anti-ganglioside complexes (GSCs) IgG antibodies have been reported in patients with Guillain–Barré (GBS) or Fisher syndrome but little is known on their presence in multifocal motor neuropathy (MMN) or other chronic immune-mediated neuropathies. We examined 24 patients with MMN, 34 with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), 23 with neuropathy associated with IgM monoclonal gammopathy (PN + IgM), 13 with GBS, 34 with motor neuron disease (MND), 24 with other neuropathies and 20 normal subjects. Patients' sera were tested by ELISA for IgM reactivity to GM1, GM2, GD1a, GD1b and GT1b and with GSCs made by any combination of two of these gangliosides. In all GM1 positive patients with MMN (11), PN + IgM (1), CIDP (1) and POEMS (1), binding to GM1 was abolished or consistently reduced when tested in GSCs also containing GD1a or other gangliosides. This only occurred in one of the three GM1 positive MND patients. In a patient with PN-IgM and anti-GM2 and GD1a IgM, both reactivities were reduced when tested in GSCs also containing GM1. New reactivities were found in a patient with CIDP and anti-GD1b IgM who presented an additional reactivity to GT1b/GM1 and GT1b/GM2 GSCs, and in one with PN-IgM who had reactivity to GM2/GD1b but not to individual gangliosides. Testing for IgM antibodies to GSCs rarely permitted to identify new reactivities in chronic immune neuropathies. IgM binding to gangliosides was however often modified in GSCs suggesting that these reactivities may be affected by contiguous gangliosides possibly influencing their pathogenicity.