Differentiation of cultured promyelocytic leukemia cells (HL-60) induced by endotoxin-treated human lung conditioned...

Serum-free conditioned medium prepared from endotoxin-treated human lung tissue contains potent differentiation activity (DA) which induces the differentiation of human promyelocytic leukemia cells (HL-60) to mature functioning granulocytes and macrophages. Upon fractionation, the DA can be separated from colony-stimulating factors (CSFs). The estimated molecular weight of DA is 23,000 d which is similar to CSF-II but is much smaller than CSF-I (50,000 d). The isoelectric point (PI) value obtained from preparative isoelectrofocusing is 5.2, which is higher than CSF-I of 4.1-4.8 but lower than CSF-II of 5.6. Using isopropanol as solvent and trifluoroacetic acid (0.2%) as ion-pair, the DA is eluted at 37% isopropanol from the C-3 column in comparison to 30% for CSF-II and 34% for CSF-I.