Antigen protection of monoclonal antibodies undergoing labelling

The effectiveness of a methodology designed to protect the antigen binding capacity of monoclonal antibodies undergoing labelling with a number of reagents was examined. The antigen binding sites of monoclonal antibodies were protected by complexing them with their antigen. Chemical modification with 6 mM of the water soluble Bolton-Hunter reagent of site protected monoclonal antibodies to glucoamylase resulted in antibodies that could tolerate a four-fold increase in reagent incorporation, without any loss of antigen binding capacity. Iodination of these antibodies (modified under site protected conditions) yielded over 70% increase in radioactivity incorporated in the active antibody fraction, compared with the incorporation into unprotected antibodies. Site protected labeling was found to be effective in retaining the antigen binding capacity of monoclonal antibodies modified with all reagents tested with the exception of chloramine-T.