Similarities between Rabbit Antibodies Produced Following Ingestion of Bovine Serum Albumin and Following Parenteral Immunization

Abstract

The immune responses of rabbits fed low concentrations of bovine serum albumin (BSA) have been characterized and compared to the immune responses of rabbits injected with BSA either i.v. or s.c. in oil. The qualities of the antibodies produced were evaluated by the following criteria: 1) the average strength of the antibody-antigen bond as measured by the effect of dilution on the antigen-binding capacity; 2) the changes in strength of the antibody-antigen bond during immunization; 3) the association of BSA binding with heavy and light immunoglobulin fractions; 4) the association of BSA binding with the γA-immunoglobulins; 5) passive hemagglutinating capacities; 6) antigen-precipitating capacities and efficiencies; and 7) alteration of antibody activity by treatment with 2-mercaptoethanol. Despite possible alteration of the antigen by digestive functions, local initiation of antibody production in lymphoid tissue associated with the gastrointestinal tract and quantitative differences among the three groups, the antibodies present in the sera from orally immunized animals qualitatively were similar to antibodies produced following parenteral immunization, as judged by the above criteria. Light as well as heavy immunoglobulins with anti-BSA activity were present in the earliest antisera from all three immunization groups. These findings and the previous demonstration that antibodies produced following oral or s.c. in oil immunization have similar immunologic specificities, suggest that most of the cellular mechanisms of antibody production basic to parenteral immunization are operative during oral immunization.