A Structural Basis for the Internal Image in the Idiotypic Network: Antibodies Against Synthetic Ab2-D Regions Cross-react with the Original Antigen

In the idiotypic cascade initiated by the random terpolymer (Glu60Ala30Tyr10)n or "GAT", we have identified, in the D region of Ab2 antibodies, either Glu-Glu-Tyr or Tyr-Tyr-Glu sequences which mimic GAT immunodominant epitopes, thus suggesting a structural basis for the internal image. Peptides containing the two D-region characteristic sequences were then synthesized and coupled to BSA. In mice, they elicited antibodies, a fraction of which recognized GAT. These observations speak in favour of the localization of an internal image of the GAT antigen in the D region of Ab2 antibodies.