Normal human pluripotential and committed hematopoietic progenitors do not express the p24 antigen detected by monoclonal antibody BA-2: implications for immunotherapy of lymphocytic leukemia

Analysis of surface antigenic determinants of hematopoietic progenitor cells has relevance both to basic biologic study of cell differentiation and to potential clinical application in the diagnosis and treatment of hematologic neoplasia. The production and characterization of monoclonal antibody BA-2 by immunization with a pre- B-ALL cell line has been reported previously. In this study we utilized complement-dependent cytotoxicity and rosette-separation with antibody indirectly coupled to ox RBC to determine if the antigen (p24) recognized by the antibody BA-2 is represented on human pluripotential (CFU-GEMM) or committed hematopoietic progenitors (CFU-GM, BFU-E, CFU- E). BA-2 showed no reactivity with normal hematopoietic progenitors by either method. In contrast, BA-2 exhibited potent complement-mediated cytotoxicity for selected ALL-derived cell lines. These results show that normal human hematopoietic progenitors do no express antigenic sites represented on ALL cells that are recognized by BA-2 and suggest that this monoclonal antibody may serve as a potent and specific agent for treatment of lymphocytic leukemia, perhaps most useful in ex vivo marrow conditioning for autologous bone marrow transplantation.