IgM monoclonal antibody against terminal moiety of GM2, GalNAc-GD1a and GalNAc-GM1b from a pure motor chronic demyelinating polyneuropathy patient: effects on neurotransmitter release

We describe a patient with a pure motor chronic demyelinating polyneuropath y with an IgM monoclonal component showing anti-GM2, GalNAc-GD1a and GalNAc -GM1b reactivity whose common epitope appears to be -[GalNAc beta1-4Gal(3-2 alpha NeuAc)beta1]. We used intracellular recording to study how IgM from this patient affected neurotransmitter release in the mouse diaphragm in vi tro. Adding serum (and specifically, the purified monoclonal IgM component) blocked the nerve-evoked response in both quantal content and evoked endpl ate potential (EPP) amplitude in a complement-independent and reversible ma nner. The IgM increased the frequency of spontaneous miniature endplate pot entials (MEPPs) in a complement-dependent and reversible manner but had no effect on MEPP amplitude. (C) 2001 Elsevier Science B.V. All rights reserve d.