Changes in the degree of galactosylation of rabbit IgG during long-term immunization with bovine serum albumin

The galactose content of isolated IgG was analyzed before immunization and at intervals during prolonged immunization over 16 months. It was found that IgGs from non-immunized and immunized animals differed in galactose content and that the galactose content of serum IgG varied during the course of the immune response. These results suggest possible intraclonal variations or the emergence of subclones of cells secreting IgG that is differently galactosylated relative to the IgG of non-immunized animals. Since isotypic polymorphism of IgG (subclasses), which determines the effector potential(s) of IgG antibodies, does not exist in rabbits, glycosylation may be what defines functional subsets of isotypically uniform antibodies produced during an immune response in these animals.