Antibodies directed against the A20 immunoglobulin Id could be detected in sera of BALB/c mice immunized with intact bsAb BiLu and A20-EpCAM cells.

This response was clearly diminished after depletion of CD4⁺ T cells in the immunization phase. The use of A20 wild-type cells and intact bsAb resulted in a weak reaction, too. For the anti-idiotypic ELISA pooled and serially diluted preimmune or immune sera were incubated on A20 Id-coated ELISA plates, followed by biotin-labeled goat antimouse IgG1 and developed with avidin-peroxidase. Preimmune sera revealed no reaction.