Complement-dependent immune damage to liposomes containing gangliosides.

Rabbit antiserum against mixed beef brain gangliosides served as an excellent source of antibodies to gangliosides GM1, GM3, GD1a, GD1b, and GT1b. Immune potency of antiserum was determined by complement-dependent damage to liposomes containing gangliosides as antigens. Antibody levels in antiserum to mixed gangliosides, when tested against individual gangliosides, were equivalent or superior to the levels obtained by immunization of rabbits with purified individual gangliosides. Naturally occurring antibodies to GM1, GD1b, and GM3 were observed in preimmunization sera. The levels of these natural antibodies, although easily high enough to serve as antiserum sources for liposome assay, were increased substantially following immunization. High titers of antibodies to GM1 and GD1b were observed in certain individual guinea pig sera, and selection of individual non-reacting guinea pig sera was necessary in order to obtain suitable complement sources when testing rabbit antibodies to liposomal GM1 and GD1b. The maximum plateau level of trapped glucose release from liposomes in the presence of saturating levels of antigen, antiserum, and complement was influenced strongly both by the method of removing untrapped glucose during liposome preparation and by the type of ganglioside incorporated into the lipid bilayer.