A monoclonal antibody cross-reactive with human platelets, megakaryocytes, and common acute lymphocytic leukemia...

A cytotoxic monoclonal antibody, CALL1, produced against a human schwannoma tumor was found to react with human platelets, common acute lymphocytic cells (cALL), and lymphoblasts from lymphoid blast crisis of chronic myelocytic leukemia (CML). The hybridoma was repeatedly cloned, and the antibody was considered reactive to a single antigen by absorption tests demonstrating that platelets remove cALL activity and cALL cells absorb platelet activity from the antibody. In addition, chromatofocusing showed that the antibody against platelets and cALL had the same isoelectric point. The CALL1 antibody bound to megakaryocytes but inhibited neither myeloid (CFU-C) nor erythroid (BFU-E) colony formation from bone marrow stem cells. Immunoprecipitation and SDS-gel electrophoresis indicated that CALL1 reacts with a polypeptide of 26,000 daltons.