Allergen-induced recruitment of FcεRI⁺ eosinophils in human atopic skin

We have attempted to identify FcεRI⁺ eosinophils in cutaneous late-phase reaction in atopic subjects biopsied at 6, 24 and 48 h after the injection of either allergen or a diluent control. Compared to the diluent sites, allergen-injected sites had significantly increased numbers of eosinophils, peaking between 6 and 24 h, of which approximately 20-30% expressed mRNA for the α, β, and γ chains of FcεRI, as shown by in situ hybridization. Using either a monoclonal or a polyclonal anti-a chain antibody, the FcεRIα protein also co-localized to approximately 50-80% of eosinophils at all time points studied. We also observed a significant correlation (r = 0.89; p = 0.02) between the numbers of FcεRI⁺ (997⁺)/EG2⁺ eosinophils and the magnitude of the late-phase reaction. Thus, a significant proportion of eosinophils infiltrating the site of allergen-induced allergic tissue reactions in atopic subjects express FcεRI. The findings show that high-affinity IgE receptors may play a role in eosinophil secretory processes in vivo.