Rabbit anti-idiotypic antibodies (aId Ab) were prepared against five murine monoclonal antibodies (mAb) specific for the rabies virus glycoprotein. Four of the mAb were directed against three known, type-specific, neutralizing sites on the glycoprotein, and the other mAb was directed against a topographically uncharacterized, nonneutralizing epitope. An absence of significant cross-reactivity among the aId Ab for heterologous mAb suggested that the aId Ab were highly specific for unique variable region determinants. The binding of three of the five aId Ab to their homologous mAb could be inhibited by rabies virus-soluble glycoprotein, suggesting that the aId Ab possessed subpopulations similar or adjacent to the antigen-binding site of the mAb. Two of the five aId Ab injected into mice elicited a specific virus-neutralizing antibody response. Mechanisms to account for the induction of the virus-neutralizing antibody by aId Ab are discussed. capsid mAb 515-3 (Y2a isotype) and 389-1 (-yl isotype) 660 on July 31, 2020 by guest