The use of tolerization in the production of monoclonal antibodies against minor antigenic determinants

An initial attempt to prepare monoclonal antibodies specific for the Dictyostelium discoideum lysosomal enzyme β-glucosidase was unsuccessful. All of the antibodies resulting from this fusion recognized an extremely immunogenic epitope that is present on all of the lysosomal enzymes of Dictyostelium. In two succeeding fusions, changes in the immunization schedule intended to increase the immune response to enzyme-specific epitopes were not entirely successful. Although nine hybridomas producing antibodies specific for β-glucosidase resulted from these two fusions, most (70%) of the cell lines isolated secrete antibodies that recognize the shared, immunodominant epitope. Moreover, the nine β-glucosidase-specific antibodies proved to be of limited utility since none recognize the native enzyme. Therefore, we attempted to tolerize a BALBc mouse to the common epitope by injecting the lysosomal enzyme, N-acetylglucosaminidase, within 40 h after birth. As an adult, this animal was immunized with β-glucosidase. Fusion of the spleen cells from this mouse with myeloma cells resulted in the isolation of nine hybridoma lines that produce antibodies specific for β-glucosidase. No antibodies reactive with the common epitope were detected. These results suggest that tolerization may provide a means whereby an undesired class of antibody-producing cell lines can be selectively eliminated from the products of a fusion.