Assessment of eosinophil and neutrophil participation in atopic dermatitis: comparison with the IgE-mediated late-phase reaction.

We hypothesized that repeated IgE-mediated late-phase reactions are critical in the pathogenesis of atopic dermatitis (AD). Prior studies have shown that extracellular deposition of eosinophil granule major basic protein (MBP) occurs in lesional AD skin, despite a paucity of infiltrating eosinophils, and that deposition of both neutrophil and eosinophil granule proteins occurs in the IgE-mediated late-phase reaction. We evaluated the participation of both eosinophil and neutrophil granule proteins in AD. Cutaneous biopsy specimens and serum and urine samples were obtained from 22 patients with AD. Lesional tissue was examined by means of immunofluorescence for neutrophil elastase and lactoferrin and for eosinophil granule MBP, eosinophil-derived neurotoxin (EDN), and eosinophil cationic protein (ECP). Serum levels of elastase, MBP, EDN, and ECP and urine levels of MBP, EDN, and ECP were measured. Marked extracellular deposition of at least one of the eosinophil granule proteins was present in the dermis of 15 of the 22 AD skin specimens, but minimal or no extracellular neutrophil elastase or lactoferrin deposition was observed in any specimens. Serum and urine levels of MBP, EDN, and ECP in the patients were elevated when compared with those of normal controls, whereas serum levels of neutrophil elastase were not elevated. Serum MPB levels correlated with extent of body surface involvement. These results suggest that eosinophil degranulation occurs in AD but that neutrophil degranulation does not. Although eosinophil degranulation is prominent in both the late-phase reaction and in AD, the lack of neutrophil degranulation in AD demonstrates differences in the inflammatory reactions.