Anti-idiotypic antibodies (anti-Ids) were raised in a rabbit against a murine monoclonal antibody (MAb) neutralizing the yeast killer toxin produced by a strain of Pichia (Hansenula) anomala. In an immunodiffusion test, the anti-Ids produced in the rabbit recognized the antigen-binding site of the MAb used as the immunogen (KT4) but not that of another heterologous MAb. The absence of any significant cross-reactivity among the anti-Ids raised in a rabbit for a heterologous MAb suggested that the anti-Ids were highly specific for unique variable-region determinants. Furthermore, the P. anomala killer toxin proved to be competing with anti-Ids for the binding site of MAb KT4. Anti-Ids against the MAb to yeast killer toxin inhibited the growth of Candida albicans, thereby mimicking the effect of the yeast killer toxin. These results suggest that, in some cases, anti-Ids might be useful tools for elucidating structure-function relationships for sensitive cell receptors.
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