Cytokine induction of granule protein synthesis in an eosinophil-inducible human myeloid cell line, AML14.

Study of eosinophil growth and differentiation has been hampered by the difficulty of obtaining adequate numbers of highly purified eosinophil progenitors or mature eosinophils for analysis. The AML14 myeloid leukemia cell line has the unusual ability to exhibit eosinophilic differentiation in response to stimulation by combinations of the eosinophil-active cytokines interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor, and IL-5. We now demonstrate that AML14 cells can be stimulated by a combination of these cytokines to produce mRNA encoding all the eosinophil granule proteins, including major basic protein (MBP), eosinophil peroxidase (EPO), eosinophil cationic protein (ECP), eosinophil-derived neurotoxin (EDN), and the Charcot-Leyden crystal (CLC) protein (eosinophil lysophospholipase). The production of the mature proteins was demonstrated by Western blotting, and ultrastructural analysis demonstrated the presence of immature secondary granules in cells that had been induced to differentiate to eosinophils. These findings demonstrate the utility of the AML14 cell line as a model for the study of cytokine induction of eosinophil growth and differentiation.