Skin eosinophilia in atopic patients

The responses of six atopic and six control patients to the intracutaneous administration of platelet-activating factor (PAF) acether, of the leukocyte secretagogue and chemoattractant f-methionyl-leucyl-phenylalanine (FMLP), and of allergens were studied. Immediate wheal-and-flare skin reactions to allergens and to PAF acether in atopic patients were the same, and when reactions were compared to reactions of nonatopic patients, these reactions to PAF acether and to FMLP were of equivalent intensity. Late-phase reactions were not observed macroscopically with allergen, PAF acether, or FMLP. The cellular responses, assessed by the Rebuck skin window technique, demonstrated a late (24 hours) eosinophilic response to the allergen and to both inflammatory agents, with 33% to 44% of intensively degranulated eosinophils. In comparison, very few, if there were any, eosinophils were observed in the nonatopic patients. Most infiltrated cells were neutrophils. The accumulation of eosinophils in atopic human skin indicates a potent eosinophilotactic activity restricted to the allergic patients. A similar cellular reaction has been observed in lungs from guinea pigs injected with PAF acether or with allergen, and in patients with severe asthma. The chemoattractant activity of FMLP toward eosinophils cannot be accounted for by its histamine-releasing activity and remains to be explained.