Elimination of Leukemic Cells from Human Bone Marrow Using Monoclonal Antibody and Complement

Human leukemic cells which bear the common acute lymphoblastic leukemia antigen can be lysed with a murine monoclonal antibody (J-5) in the presence of rabbit complement. Conditions have been defined for eliminating ⁵¹Cr-labeled common acute lymphoblastic leukemia antigen-positive NALM-1 cells or cryopreserved leukemic lymphoblasts from a 100-fold excess of human bone marrow. Optimal lysis is obtained with treatment for a total of 90 min. Three treatments for 30 min are more effective than two treatments for 45 min or one treatment for 90 min. Separation of marrow on a Ficoll:diatrizoate gradient does not permit more effective elimination of leukemic cells. Tumor cell lysis is inhibited by high concentrations of common acute lymphoblastic leukemia antigen-positive cells (2x10⁷/ml) and by high concentrations of bone marrow (10⁸/ml). Under optimal conditions, >99% of ⁵¹Cr-labeled leukemic lymphoblasts can be eliminated from a 100-fold excess of human marrow. Selective removal of leukemic cells from human bone marrow in vitro should facilitate trials of autologous marrow transplantation.