High‐affinity immunoglobulin E receptor (FcεRI)‐bearing eosinophils, mast cells, macrophages and Langerhans’ cells in allergen‐induced late‐phase cutaneous reactions in atopic subjects

Abstract

We have used in situ hybridization (ISH) and immunohistochemistry (IHC) to investigate the kinetics of the expression for FcεRI mRNA (α‐, β‐ and γ‐chains), the α‐chain protein product, as well as the phenotype of the mRNA‐ or protein‐positive cells in allergen‐induced late‐phase skin reactions in atopic subjects. Compared with diluent controls, there were significant increases in the total numbers of mRNA⁺ cells for the α‐, β‐and γ‐chains for FcεRI at all time‐points (6, 24 and 48 hr) after allergen challenge (P+ macrophages, eosinophils, mast cells and CD1a⁺ cells were also observed after allergen challenge (P+ co‐localization was CD68⁺ macrophages (42–47%), EG2⁺ eosinophils (33–39%), tryptase⁺ mast cells (5–11%) and CD1a⁺ Langerhans’ cells (2–4%). Using single IHC, significant increases in the total number of FcεRI protein⁺ cells (P+ cells was tryptase⁺ mast cells (33%), CD68⁺ macrophages (36%), EG2⁺ eosinophils (20%), CD1a⁺ Langerhans’ cells (4%) and unidentified cells (7%), at the 24‐hr allergen‐challenged sites. These observations suggest that the cutaneous late‐phase reaction in man is associated with up‐regulation of FcεRI on eosinophils, macrophages, mast cells and Langerhans’ cells.