Selective killing of leukaemia cells by antibody-toxin conjugates: Implications for autologous bone marrow transplantation

The recent development of tumour-reactive monoclonal antibodies has stimulated interest in their use in targeting toxic agents to tumour cells. One such approach involves the covalent coupling of tumour-reactive antibodies to the toxic peptide of the plant toxin, ricin. Such conjugates are highly effective in killing various tumour cells in vitro^1-6. Here we have used the murine B-cell tumour, BCL₁, in an adoptive transfer system capable of detecting 1-10 tumour cells, to demonstrate the effectiveness and specificity of an anti-immunoglobulin(Ig)-ricin A chain conjugate in deleting tumour cells from infiltrated murine bone marrow. We report that the transferred cells were able to repopulate the haematopoietic system of lethally irradiated mice and that in most mice the tumour did not recur. We discuss the implications of this approach for autologous bone marrow transplantation following supralethal tumour therapy.