Gangliosides GM1 and GD1b are antigens for IgM M-protein in a patient with motor neuron disease.

We studied a patient with an IgM M-protein and lower motor neuron disease to identify the antigens to which the M-protein bound. Gangliosides from peripheral nerve and spinal cord were separated by high-performance thin-layer chromatography and immunostained with the patient's serum. The serum IgM immunostained two gangliosides identified as GM1 and GD1b, and immunostaining was specific for the M-protein light chain type. IgM-binding to the two gangliosides was detectable by ELISA at serum dilutions of greater than 1:10,000, and the M-protein was selectively immunoabsorbed by liposomes containing GM1 or GD1b. The IgM M-protein also bound to asialo-GM1, indicating reactivity to the galactosyl(beta 1-3)N-acetylgalactosaminyl moiety shared by GM1, GD1b, and asialo-GM1.