Despite the observation that eosinophilic tissue infiltration is a predominant feature of IgE- mediated allergic inflammatory responses, the specificity and relationship of eosinophil migration and activation in allergic asthmatic patients to the clinical expression of asthma remains to be fully defined. To establish the mechanisms underlying eosinophilic inflammation and their role in the pathogenesis of asthma, it is essential to ascertain the factors that regulate the initiation and persistence of this process in the lung. Cytokines play a critical role in eosinophil regulation and interleukin (IL)-5 is a particularly potent and selective EOS activator. To more directly assess the mechanisms contributing to airway inflammation and regulation of EOS movement to and within the lung, we have used bronchoscopy to perform segmental bronchoprovocation with antigen followed by lavage. From this approach, preliminary evidence has shown that the release of IL-5 from airway cells is enhanced in asthma; airway CD4+ lymphocytes are a primary, but not unique source of IL-5; and the cytokine profile of airway cells in asthma, but not in allergic rhinitis, includes the TH1- type cytokine interferon (IFN)-gamma. Based upon these observations, it is hypothesized that enhanced generation of IL-5 is a distinguishing feature of asthma, and that this increase is caused by abnormal regulation of IL-5 from airway lymphocytes. The overall goals of this project are to establish the cell source and phenotype for IL-5 in asthma, the relationship of IL-5 in asthma, and to more directly assess the mechanisms underlying airway inflammation and regulation of EOS movement to and within the lung and the uniqueness of these responses to asthma. To accomplish these aims, allergic rhinitis and normal subjects will undergo bronchoscopy and segmental bronchoprovocation with antigen and lavage. Airway cells retrieved before and after antigen challenge will be cultured, activated, and the IL-5 production measured. The generation of Il-5 release will be compared to BAL fluid cytokine and airway cell mRNA for IL-5 by RT-PCR. Flow cytometry will be used to establish the cell phenotype and expression of intracellular cytokine protein in airway cells; in addition, cell depletion studies of airway cells and RT-PCR will determine cytokine production and presence of cytokine mRNA of subpopulations of airway lymphocytes. Regulation of Il-5 production from airway cells will established by co-incubation experiments with specifically identified regulatory cytokines (in particular, INF-gamma) and will be the first mechanistic information on IL-5 generation and regulation of EOS attraction of the airway and elucidate the specificity of these processes to asthma.
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