Characterization of eosinophils and detection of eotaxin in skin chamber fluid after challenge with relevant allergen in patients with mild asthma

Background A selective recruitment of eosinophils to sites of allergic infl ammation is suggested to be controlled by regulation of cytokines, chemokin es and adhesion molecules. Objective The aim of this study was to examine whether allergen challenge i n skin chambers, applied on patients with allergic rhinitis and mild asthma , results in a selective influx of activated eosinophils and detectable lev els of cytokines/chemokines related to eosinophil recruitment, such as inte rleukin (IL)-5 and eotaxin. Methods A skin blister was induced on the volar aspect of each forearm; one contained PBS-heparin buffer (control) and the other was challenged with r elevant allergen. Peripheral blood was drawn before the allergen was applie d to the skin chamber, and the expression of CD9, CD11b and EG2-epitope on intracellular eosinophil cationic protein (ECP) was analysed in eosinophils . Chamber fluid was collected sh after allergen application and analysed fo r differential cell counts, expression of eosinophil activity markers, the presence of ECP, eotaxin, and IL-5. Results The number of recruited leucocytes was equal in the allergen-challe nged chambers and in controls. However, the number of eosinophils was signi ficantly increased in the allergen-challenged chambers, and elevated levels of released ECP were measured. Moreover, the eosinophils recruited were ac tivated, as shown by increased expression of EG2 and CD11b, and decreased e xpression of CD9, in comparison with blood eosinophils. In the skin chamber fluids, higher levels of eotaxin were detected in the allergen-challenged chambers than in controls, but there were no detectable levels of IL-5. Conclusion We have demonstrated a selective recruitment of eosinophils, and higher levels of released ECP and eotaxin, in skin chambers stimulated wit h allergen, as compared with control chambers. Allergen challenge in skin c hambers is a useful tool for studies of eosinophil recruitment, their state of activation, and their involvement in the allergic inflammatory response .