AN AFFINITY COLUMN METHOD FOR DETERMINATION OF THE IMMUNOREACTIVITY OF I-131 CHIMERIC L6 MONOCLONAL-ANTIBODY AND COMPARISON TO IN-VIVO TUMOR-LOCALIZATION

An affinity column method was developed to determine the immunoreactiv ity of I-131-ChiL6 (chimeric L6 monoclonal antibody), a candidate for radioimmunotherapy. This method involved assessing the binding of the radiolabeled antibody to antigen containing membranes bound to a React i-gel agarose matrix. The immunoreactivity determined by the affinity column method correlated to other in vitro binding assays including th e Lindmo infinite antigen excess method. In tumor-bearing mice which h ad been injected with I-131-ChiL6, which possessed high immunoreactivi ties (90-82%), a high tumor uptake (13.5-10.5% ID/g) was observed. A d ecrease in tumor uptake (5.2-4.8% ID/g) was observed with I-131-ChiL6 samples of low immunoreactivity (42% and 31%, respectively). While a m oderate loss of immunoreactivity (4-18%) of the I-131-ChiL6 samples co uld be detected by the affinity column method, the loss of tumor uptak e in vivo observed was not as significant. This method was found to be an efficient and sensitive method for detecting damage to the antibod y during radiolabeling and applicable as a quality control method for clinical trials. This rapid method, compared to the other in vitro bin ding assays (including the Lindmo infinite antigen excess method) has distinct advantages as a quality control method since it requires less manipulation and can be semi-automated.