Preexisting human anti-murine antibodies and the effect of immune complexes on the outcome of immunoscintigraphy.

Radiolabeled monoclonal antibodies (MoAb) are useful in radionuclide imaging. Human anti-murine antibodies (HAMA), however, could produce immunologic effects or alter the outcome of immunoscintigraphy. Three patients are reported who had been exposed previously to radiolabeled MoAbs and in whom subsequent immunoscintigraphy was performed. All patients showed abnormal biodistribution of the antibody and increased hepatic uptake. Human anti-murine antibody was demonstrated in all patients. These results indicate that immune complexes are formed after HAMA-MoAb reaction and are then phagocytosed by cells of the reticuloendothelial system.