Selective growth response to IL-3 of a human leukaemic cell line with megakaryoblastic features

A new human leukaemic cell line (M-O7) with the phenotypic characteristics of CFU-mega is described. Its cells are positive for T200 leucocyte common antigen (LCA) and negative with MAbs recognizing T and B cells and mature myelomonocytic antigens. In contrast, they react with MAbs recognizing antigenic determinants common to multi-lineage (CD13, CD33, CD34) and to bipotent erythromegakaryoblastic (CD36, H25) haemopoietic precursors, and with MAbs specific for platelet glycoproteins (CD41w, CD42w). A small proportion (10%) of the cells were large and multinucleated, and on electron-microscopy examination showed peripheral splitting of platelet-like cytoplasm particles. When transferred to a serum-free Iscove modified Dulbecco's medium supplemented with human insulin and transferrin, M-O7 cells stop proliferating. Of the haemopoietic growth factors tested for their ability to restore the proliferative activity of this quiescent population, only rH IL-3 proved effective. Moreover, it also increased the cloning efficiency in methylcellulose more than any other CSFs. The M-O7 cell line may provide a valuable tool for the biological assay of IL-3, and a model for biochemical studies of the megakaryocytic lineage.