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 inflammation is suggested to be controlled by regulation of cytokines, chemokines and adhesion molecules. Objective The aim of this study was to examine whether allergen challenge in skin chambers, applied on patients with allergic rhinitis and mild asthma, results in a selective influx of activated eosinophils and detectable levels of cytokines/chemokines related to eosinophil recruitment, such as interleukin (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 relevant allergen. Peripheral blood was drawn before the allergen was applied 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 8 h after allergen application and analysed for 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‐challenged chambers and in controls. However, the number of eosinophils was significantly increased in the allergen‐challenged chambers, and elevated levels of released ECP were measured. Moreover, the eosinophils recruited were activated, as shown by increased expression of EG2 and CD11b, and decreased expression 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 with allergen, as compared with control chambers. Allergen challenge in skin chambers is a useful tool for studies of eosinophil recruitment, their state of activation, and their involvement in the allergic inflammatory response.