Isoelectric focusing spectra of rabbit antibodies to Salmonella abortus-equi detected by anti-idiotypic sera

Serum antibodies from rabbits hyperimmunized with Salmonella abortus-equi (S.a-e) were examined by isoelectric focusing in polyacrylamide gel, followed by the coating of the gel with iodinated polysaccharide extracted from bacterial cell walls. The antibody populations in these sera were highly heterogeneous. Anti-idiotypic sera, prepared in allotypically matched rabbits, recognized only a fraction of these antibody populations (generally from one to three clonal antibodies per serum). Different rabbits subjected to the same anti-idiotypic immunization can recognize different antibodies in the same serum to S.a-e.

Homologous and heterologous idiotypes recognized by the same anti-idiotypic serum have shown very similar but never identical pI spectra. It appears that the same group of idiotypic determinants can be markers for several clonal antibodies and are not unique to a single clone.

Two rabbits were studied throughout an immunization course lasting 2 years; we did not observe any change in the clonal product of antibody-producing cells carrying the idiotypic determinants.