Expression of a 21KD Molecule on Hematopoietic Progenitor Cells

A monoclonal antibody (MoAb) K15 (IgG3) was obtained by fusion between SP2/0, mouse myeloma cell line and spleen cells from BC3Fl mice immunized with K562. a chronic myelocytic leukemia (CML) blastic crisis cell line. MoAb Kl5 precipitated a 21 kilodalton (KD) polypeptide in reduced condition. It stained lymphocytes, monocytes, eosinophiles and small bone marrow cells, but not neutrophiles, platelets, red blood cells (REC) and large bone marrow cells. Depletion of K15+ cells abolished both colony-forming units-granulocyte/monocyte (CFU-GM) and burst-forming units-erythroid (BFU-E). Thus MoAb Kl5 identifies antigens expressed on hematopoietic progenitor cells. The selective retention of this antigen by certain cell lineages may suggest some functional role of this antigen.