Mouse L1210V leukemia as a model to analyse efficiency of leukemic cell elimination by immunotoxin, antibody and complement, and cytostatic agents

In an attempt to eliminate selectively mouse L1210V leukemic cells from infiltrated bone marrow, the immunotoxin MoAb-16-RTA composed of monoclonal antibody recognizing oncofetal antigen on L1210V cells and the ricin A chain was prepared. The immunotoxin exhibited an antigen-specific, dose-dependent cytotoxic effect in vitro. One hour's exposure of leukemic cells to 10(-6) M of immunotoxin appeared to be sufficient to kill all leukemic cells. In the experimental conditions applied, a complete elimination of L1210V cells from leukemic bone marrow was achieved. MoAb-16 antibody and complement in the same experimental protocol, the bone marrow purging was not complete. The surviving leukemic cells were still able to grow and kill recipient mice. The in vitro exposure to immunotoxin or to antibody and complement was not toxic to normal bone marrow progenitors. The exposure of leukemic cells to selected cytostatic agents of the oxazaphosphorine group appeared to be effective in the elimination of leukemic cells, but doses required for killing leukemic cells were highly toxic to normal bone marrow progenitors.