Isolation and characterization of two new monoclonal antibodies against the CD34 molecule

Two new monoclonal antibodies, Immu-133 and Immu-409, were raised against the human acute myelogenous leukemia cell line (KG-1a) and human immature erythroleukemic cells (TF1). These monoclonal antibodies were isolated from two different fusions of mouse myeloma cells with mouse splenic lymphocytes. The immunofluorescence studies performed on various target cells showed that these antibodies recognized a surface antigen expressed selectively on KG-1a, TF1 cells and on human hematopoietic progenitor cells. They also stained endothelial cells used in immunochemistry both in frozen and paraffin embedded tissue sections. Immu-133 and Immu-409 immunoprecipitated a KG-1a cell surface protein with an apparent molecular weight of 110-115 Kd. Competitive binding assays performed with a panel of referenced CD34 monoclonal antibodies revealed that Immu-133 and Immu-409 are monoclonal antibodies restricted to different epitopes of the CD34 molecule.