[Chronological analysis of eosinophil infiltration in mite-allergen induced dermatitis in atopic patients]

To elucidate the active process of eosinophil infiltration in atopic dermatitis (AD), we performed patch testing using crude mite allergens on normal-appearing skin in adult AD patients with high levels of mite-specific IgE antibodies and analyzed positive reaction sites chronologically by histological and immunohistological methods. Positive reactions were observed in 6 out of 9 AD patients (66.7%), whereas none of 7 non-AD control subjects showed positive reactions. Skin biopsies were obtained from positive reaction sites at 2,6,12,24 and 48 hours after allergen challenge. Eosinophils were seen within postcapillary venules at 2 hours, followed by increased perivascular eosinophil infiltration at 6 hours which peaked at 24 and 48 hours. Epidermal eosinophilic spongiosis was also observed at 48 hours. The majority of infiltrating eosinophils showed positive reactions for BMK-13 and 15-59% of them were EG2 positive activated eosinophils. BMK-13, EG2 and anti-EP positive reactions were scattered throughout connective tissue and their areas were time-dependently increased. These findings suggest that eosinophil transmigration and activation play an important role in initiating early AD lesions induced by transepidermal mite allergen permeation.