Binding of immunoglobulin G antibodies in Guillain-Barré syndrome sera to a mixture of GM1 and a phospholipid: possible clinical implications.

Anti-GM1 immunoglobulin G (IgG) antibodies are frequently present in sera from patients with Guillain-Barré syndrome (GBS). A previous report on a patient who had a neuropathy with immunoglobulin M (IgM) M-protein binding to a conformational epitope formed by phosphatidic acid (PA) and gangliosides prompted us to investigate the binding of IgG antibodies in GBS sera to a mixture of GM1 and PA (GM1/PA). Of 121 GBS patients, 32 had anti-GM1 IgG antibodies. All 32 also had antibody activity against GM1/PA. Twenty-five (78%) of 32 patients had greater activity against GM1/PA than against GM1 alone. Twelve patients who had no anti-GM1 IgG antibodies had IgG antibody activity against GM1/PA. No GBS patient had IgG antibody against PA alone. In contrast, two rabbit anti-GM1 antisera had greater activity against GM1 alone than against GM1/PA. IgG antibody with greater binding activity against a mixture of GM1 and a phospholipid than against GM1 alone may have an important role in the pathogenesis of GBS and has implications for diagnosis.