Chronologic analysis of in situ cytokine expression in mite allergen-induced dermatitis in atopic subjects.

Patch testing with crude dust mite extracts, after removal of horny epidermal layers, was performed on normal-appearing skin of nine adult patients with atopic dermatitis who had high mite-specific IgE antibody levels. Positive skin reactions were observed in seven subjects. Skin biopsy specimens were obtained from positive reaction sites at 2, 6, 12, 24, and 48 hours after allergen challenge and subjected to histologic and immunohistochemical studies and extraction of RNA. Perivascular infiltration of small mononuclear cells began at 2 hours, followed by eosinophilic infiltration at 6 hours, which peaked at 24 and 48 hours. Increased expression of IL-4 messenger RNA was detected with reverse-transcription polymerase chain reaction at 12 and 24 hours, whereas immunohistochemical staining with anti-IL-4 antibody showed positive reactions in connective tissue around infiltrating cells after 2 hours. Expression of IL-5 and tumor necrosis factor-alpha mRNA was upregulated 2 hours after an application of allergen. Interferon-gamma mRNA was not detected. These findings suggest the crucial role of TH2-type cytokines in initiating eosinophil infiltration of mite allergen-induced dermatitis in patients with atopic dermatitis.