High-titre IgM anti-sulfatide antibodies in individuals with IgM paraproteinaemia and associated peripheral neuropathy

The common association between monoclonal gammopathy and peripheral neuropa thy was studied in seven patients with demyelinating polyneuropathy and IgM paraproteinaemia. Plasma samples from these individuals were thoroughly te sted for antiperipheral nerve myelin (PNM) antibodies and then screened for glycoprotein and glycolipid reactivity by western immunoblotting and thin- layer chromatography (TLC) immunostaining. Three of the seven samples showe d strong IgM anti-PNM and antisulfatide (GalS) antibody reactivity. Two of these three plasma samples showed extraordinarily high antisulfatide IgM an tibody titres, ranging from 1 x 10(4) to 1 x 10(6) arbitrary units/L. These same samples also showed intense myelin staining of sciatic nerve sections (paraffin and cryostat) and teased nerve fibres. No axonal immunoreactivit y was observed. These results suggest that high titre IgM antisulfatide ant ibodies may play a pathogenetic role in the immune demyelination associated with IgM paraproteinaemia.