Production of a human monoclonal antibody recognising a determinant on mouse IgG2b from a patient receiving mouse monoclonal antibody for diagnostic imaging.

The development of human antibodies recognising mouse immunoglobulins represents an obstacle to effective antibody therapy. This study shows that patients produce modest titres of antibodies (predominantly anti-mouse rather than anti-idiotypic) after a single low-dose injection for immunoscintigraphy, suggesting that repeated imaging with the same or a different antibody could be a problem. Fusion of the lymphocytes from a patient who had been imaged twice previously resulted in a monoclonal antibody that specifically binds to an IgG2b isotypic determinant. Anti-IgG2b antibodies predominated in this patient's serum. Production of human monoclonal antibodies from patients given mouse monoclonal antibodies not only allows a finer dissection of the immune repertoire but also provides possible reagents for controlling the human anti-(mouse Ig) response, for selection of class-switch variants of mouse monoclonal antibodies and enhancing tumour imaging.