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Generation of a conditionally immortalized myeloid progenitor cell line requiring the presence of both interleukin‐3 and stem cell factor to survive and proliferate

Summary. The H‐2Κb temperature‐sensitive (ts) A58 transgenic (Immorto) mouse has been used previously to generate conditionally immortalized cells from a number of tissues. The present study aimed to investigate characteristics of primitive myeloid precursor cells derived from H‐2Κb‐tsA58 bone marrow. Cell populations were enriched for granulocyte/macrophage progenitors by centrifugal elutriation, and were cultured in the presence and absence of cytokines at the permissive and restrictive temperatures for the A58 oncogene. Cells derived from H‐2Κb‐tsA58 mice required both A58 activation and the growth factors, stem cell factor (SCF) and interleukin‐3 (IL‐3), for long‐term cell survival and growth; cells were maintained for > 300 d in culture under these conditions. IL‐3‐ and SCF‐dependent clonal cell lines were derived with a phenotype (lin–, Sca‐1+, CD34+, ER‐MP 58+, ER‐MP 12+, ER‐MP 20–) characteristic of primitive myeloid progenitors. These cells differentiated on addition of granulocyte/macrophage colony‐stimulating factor (GM‐CSF) or macrophage colony‐stimulating factor (M‐CSF) and acquired mature cell morphology with some upregulation of differentiation markers. In conclusion, the A58 oncogene can immortalize haemopoietic progenitor cells. These cells require two cytokines for growth, IL‐3 and SCF; as such, they constitute a useful resource for the study of synergistic interactions between growth factors. The ability to develop monocytic cell characteristics also permits the investigation of cytokine‐mediated early haemopoietic progenitor cell development.