The role of interleukin-5, interleukin-8 and RANTES in the chemotactic attraction of eosinophils to the allergic lung

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Abstract
Bronchoalveolar lavage (BAL) fluid from patients with birch-pollen allergy lavaged during the season showed an elevated chemotactic activity for eosinophils compared with BAL fluid from the same patients before the start of the season. The aim of this study was to identify the eosinophil chemotactic agents in the BAL fluid, to compare these findings with in vitro studies on selected cytokines, and to investigate the interactions between these cytokines. Neutralizing antibodies for interleukins (IL) -2, -5 and -8, RANTES and leukaemia inhibitory factor (LIF) were added to the BAL fluid, and the chemotactic activity was tested with eosinophils from allergic donors. Eosinophils from healthy donors were preincubated with IL-5 in order to mimic the primed state of eosinophils from allergics, and the migration towards recombinant IL-5, IL-8, and RANTES in different combinations was measured. Eosinophils from allergic donors were also used. Anti-IL-5, anti-IL-8 and anti-RANTES inhibited the chemotactic activity in the BAL fluid. Recombinant RANTES induced migration, which was enhanced by preincubation of the cells with IL-5. Only eosinophils from symptomatic allergics responded to IL-8, and IL-5 was not sufficient to prime normal eosinophils in vitro to an IL-8 response. A negative correlation was found between the level of in vivo activation of the cells and their response to IL-5, and a positive correlation with the response to RANTES. IL-8 and RANTES are important for eosinophil accumulation to the lung of pollen-allergic asthmatics. IL-5 alone may not be responsible for the priming of eosinophils in vivo, but is an essential cofactor for the other chemoattractants.

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