Studies of differential gene expression in clinically derived eosinophil populations

Background Influx of eosinophils into the post-capillary bronchial epitheli um and the subsequent release of inflammatory mediators is characteristic o f the late phase of asthmatic attacks. The genes that serve to predispose t he peripheral blood eosinophils of asthmatics to undergo this process are p oorly defined. The aim of this report is to describe the differential gene expression of both the known pro-inflammatory genes 5-lipoxygenase and 5-li poxygenase-activating protein (FLAP) and novel cDNA sequences in eosinophil s derived from clinical samples. Methods Novel cDNA sequences representing genes upregulated in peripheral b lood eosinophils of asthmatic as compared with nonasthmatic patients were i dentified by differential display polymerase chain reaction (DDPCR). The di fferential expression of these sequences, in addition to known pro-inflamma tory genes, were then studied by reverse dot blotting of amplified RNA gene rated from the eosinophils of nonasthmatic donors, asthmatic donors, asthma tic donors taking steroids, interleukin (IL) -3, IL-5, granulocyte-macropha ge colony stimulating factor- (GM-CSF) treated eosinophils from asthmatic d onors and the eosinophilic cell line AML14. Results Four unique DDPCR-generated 3'UTR DNA fragments were identified tha t showed differing patterns of expression between the eosinophil population s of interest. Expression of each of the novel clones was increased in the peripheral blood eosinophils of asthmatics and downregulated in those donor s taking steroids. Expression of 5-lipoxygenase was not found to vary betwe en the different eosinophil populations, whereas FLAP was induced by treatm ent with the cytokine cocktail in both primary eosinophils and the eosinoph ilic cell line AML14. Conclusion The differential regulation of the novel cDNA sequences and FLAP in the range of eosinophil populations studied suggest that they may provi de clinically relevant therapeutic targets. Moreover, the procedures used i n these studies may provide a general approach to the study of differential gene expression in small numbers of cells such as those obtained from clin ical samples.