Localization of interleukin-13 gene-expressing cells in tuberculin reactions and lesional skin from patients with atopic dermatitis

Interleukin (IL)-13 is a cytokine thought to play an important role in IgE- mediated allergic reactions, The aims of the present study were to localize IL-13 mRNA in positive tuberculin reactions and atopic dermatitis lesions using in situ hybridization and to study the possible influence of atopy on the cytokine gene expression in tuberculin reactions. Punch biopsy specime ns were taken from tuberculin reactions in 17 nonatopic and 12 atopic (Phad iatop positive), but otherwise healthy, individuals 72 h after injection of purified protein derivative, from chronic lichenified lesions and nonlesio nal skin in six patients with atopic dermatitis and from normal skin in 12 healthy individuals. IL-13-mRNA-producing cells were located mainly in the dermal-cell infiltrates, both in atopic dermatitis lesions and tuberculin r eactions. In the atopic dermatitis lesions, IL-13-mRNA expression was found in close apposition to the epidermis, Higher numbers of IL-13-mRNA-produci ng cells were observed in the dermal-cell infiltrates of chronic lichenifie d skin lesions of patients with atopic dermatitis (13.3 cells/mm(2), range 0.6-42.4 cells/mm(2)) than in the tuberculin reactions (1.1 cells/mm(2), ra nge 0-3.8 cells/mm(2)) (P < 0.01) despite the larger cell infiltrates in th e tuberculin reactions. No significant difference in IL-13 or interferon-ga mma gene expression in the tuberculin reactions was seen between atopic and nonatopic individuals.