ASSAY FOR THE DETECTION OF ANTIIDIOTYPIC ANTIBODIES TO MONOCLONAL-ANTIBODY B72.3

The administration of xenogenic monoclonal antibodies (MAbs) leads in many cases to a host immune response represented by the generation of antibodies that can be directed against allotypic, isotypic, and idiotypic determinants present on the xenogeneic MAb. Anti‐idiotypic antibodies (Ab2s) can be detected by measuring their specific reactivity in sandwich assays using their ability to cross‐link labeled Abl to Abl attached to a solid phase; however, when the MAb used for these studies reacts with a multideterminant tumor‐associated antigen found in the circulation (e.g., TAG‐72), the utility of these anti‐idiotype assays may be limited. To determine the levels of anti‐idiotypic antibodies that could be detected in patients undergoing MAb B72.3‐based immunodiagnostic and immunotherapeutic protocols, we investigated the ability of a solid‐phase sandwich radio‐immunoassay (RIA) to detect anti‐idiotypic antibodies raised against 872.3. Furthermore, to overcome the interference of circulating TAG‐72 and for antibodies to allotypic and isotypic determinants in the evaluation of an anti‐idiotypic response, we developed a methodology using CC49‐coated resin to adsorb the interfering molecules (CC49 is a second anti‐TAG‐72 MAb). Under the conditions established, all of the TAG‐72 antigen was removed by adsorption with MAb CC49. Furthermore, since the treatment used an isotype‐identical murine MAb, the binding due to the anti‐mouse antibodies, other than the anti‐idiotype, was completely abolished after a treatment with MAb CC49, leaving only the anti‐idiotype component. Analysis of serum samples from patients who had received 872.3 that were positive for human anti‐mouse antibodies in the 872.3 sandwich RIA, after the adsorption with CC49 resin, revealed the presence of a 872.3–binding component in 2 of 12 samples. The ability of the adsorbed sera to compete with an anti‐B72.3‐idiotype MAb for the binding sites present on the MAb 872.3 confirmed the anti‐idiotypic nature of the component being detected in the patient sera. Copyright © 1990 Wiley Periodicals, Inc., A Wiley Company