IMMUNOGLOBULIN SUBCLASS DISTRIBUTION AND BINDING CHARACTERISTICS OF ANTI-GQ1B ANTIBODIES IN MILLER-FISHER-SYNDROME

Circulating IgG antibodies to carbohydrate determinants on GQ1b gangli oside are found in the acute phase sera of patients with Miller Fisher syndrome, a variant of Guillain-Barre syndrome. Here we report that t he IgG subclass distribution of the anti-GQ1b antibodies is mainly res tricted to IgG1 and IgG3 antibodies; subclasses typically associated w ith a T cell-dependent immune reponse to protein antigens. This is hig hly unusual in that IgG responses to carbohydrate determinants are typ ically of the IgG2 subclass. Anti-GQ1b antibodies also have a limited ability to bind GQ1b in a membrane-like environment, particularly at b ody temperature. These data suggest that the antigen initiating the im mune response in MFS is not likely GQ1b but an unidentified cross-reac tive glycoprotein antigen(s). Similar results were obtained for anti-G M1 IgG antibodies in Guillain-Barre syndrome.