Two separate differentiation inducing proteins for human myeloid leukemia cells and their isolation from normal...

Conditioned medium from mitogen stimulated normal peripheral blood lymphocytes (PBL) has been demonstrated to contain a maturation inducer activity mediating the differentiation of human myeloid leukemia cells to monocytes and macrophages. The maturation inducer activity was isolated by salt precipitation, Sepharose CL-6B ion exchange and affinity chromatographies and electrophoresis. Two separate activities with M.W. ranges of 52-56 and 32-35 kDa capable of mediating the terminal differentiation of leukemic HL-60 promyelocytes to monocytes and macrophages were detected. The higher molecular weight species was determined to be a 54 kDa single polypeptide and was found to be distinct from IL-3 and IL-6 by ELISA and differentiation blocking assay. The inducing activity of the 32-35 kDa material was largely neutralized after treatment with anti-IL-3, but not with other antibodies. Employing the immunofluorescent antibody technique, the 54 kDa protein was detected on the surface membranes of PBL. The proportions and number of maturation inducer bearing lymphocytes in patients with acute myelogenous leukemia (0.4% and 35/mm3, respectively) were significantly lower than that of healthy donors (7.9% and 178/mm3) The role of these physiological factors in leukemia cell differentiation is discussed.