A study has been made of the production of antiidiotypic antibodies (anti-antibodies) arising during the immunization of 39 rabbits with 19 individual samples of rabbit anti-Proteus vulgaris x 19 antibodies adsorbed onto bacilli. In addition to the regular demonstration of antiidiotypic antibodies attention is drawn to the frequent occurrence of antiallotypic antibodies against molecules of immunoglobulin classes other than IgG, especially macroglobulins, which may arise during such immunization. In four cases attempts to raise autoantiidiotypic antibodies were unsuccessful, as expected.
The idiotypic specificities (antigenic determinants) have been found mainly on IgG but also sometimes on IgM molecules. The individual specificity of the antiidiotypic antibodies appears to be absolute, as long as the antiallotypic antibodies are recognized and excluded; e.g., each idiotypic specificity is characteristic of only one single rabbit and of a single kind of antibody within that rabbit. These principles hold even when antibodies of rabbit families are examined: the parental idiotypic determinants could not be found in the offspring.
In two samples tested the idiotypic specificities were found on the Fab fragment of IgG molecule but not on its antibody-combining site.