CHARACTERIZATION OF EOSINOPHILS GENERATED IN-VITRO FROM CD34(-BLOOD PROGENITOR CELLS() PERIPHERAL)

Methods for isolation and cultivation of CD34(+) peripheral blood prog enitor cells (PBPCs) have facilitated their use in autologous transpla ntation and as potential targets for gene therapy. In this work, we pr esent the possibility of using these isolated cells to study lineage-s pecific hematopoietic differentiation. We have shown that differentiat ing PBPCs faithfully replicate transcriptional events that occur durin g maturation of the eosinophil lineage; messenger RNAs encoding the fi ve eosinophil granule proteins were detected by reverse-transcriptiont ase polymerase chain reaction (RT-PCR) after 2-3 days of cytokine-stim ulated growth. Only three of the five proteins were detected by immuno fluorescence staining after 14 days of cytokine-stimulated growth; the percentage of Charcot-Leyden crystal protein (CLC)-containing cells ( 16-18%) exceeded that of eosinophil peroxidase (EPO)-containing cells (7-8%), which in turn exceeded that of eosinophil-derived neurotoxin ( EDN)-containing cells (2-4%). While the electrophoretic mobilities of both CLC and EPO synthesized by differentiating PBPCs were similar to those of their normal counterparts, immunoreactive EDN was found to be heterogeneous and of higher molecular weight than EDN found in mature eosinophils. It is not clear whether our results, which show progress ive, but incomplete, differentiation of PBPCs into eosinophils, reflec t a lack of knowledge as to what factors are essential for complete di fferentiation in vitro or relate to the inherent capacity of PBPCs to differentiate along this lineage.