Eosinophil infiltration into human skin is antigen-dependent in the late-phase reaction

Eosinophils play a critical role in late-phase reaction allergic inflammatory responses, although the factors responsible for selective tissue eosinophilia are currently ill-defined. To determine whether recruitment of eosinophils is allergen-specific, or a feature of inflammation in allergic individuals, we have examined cutaneous cell infiltrates and endothelial cell adhesion molecule expression in atopic subjects 6 h (n = 8) and 24 h (n = 7) following ultraviolet-B (UVB) irradiation, or intradermal injection of late-phase reaction allergens or diluent control, using standard immunohistochemical techniques. The numbers of eosinophils were increased significantly, when compared to controls, at both 6 h (P < 0.01) and 24 h (P < 0.05), following intradermal allergen challenge, whereas no significant increase in eosinophils was observed following UVB irradiation. UVB and allergen both induced significant increases in neutrophils, monocytes and T cells at 24 h compared to control sites. An increased expression of endothelial cell adhesion molecules, E-selectin and intercellular adhesion molecule-1 (ICAM-1), was observed in both models of inflammation. Vascular cell adhesion molecule-1 (VCAM-1) was induced weakly on some biopsies following allergen, and not at all following UVB. These data indicate that eosinophil infiltration in susceptible individuals is a specific property of allergen. Although this study would support the postulated role of VCAM-1 in selective eosinophil recruitment, given its variable and weak expression, additional factors are likely to be involved.