Background: Atopic dermatitis (AD) is a chronic relapsing inflammation usually observed in patients with an individual or a familial history of atopic diseases, precipitated by environmental factors including mite antigens (Ag). However, the exact etiology of AD is unclear. To further explore the pathogenesis and treatment of AD, a suitable animal model is necessary. In this study, we developed a new animal model of AD induced by mite Ag in NC/Nga mice. Methods: We injected the extracts of mite Ag intradermally at the ventral side of the ear of SPF NC/Nga mice on days 0, 2, 4, 7, 9, 11, 14 and 16, and measured the clinical symptoms and the ear thickness. On day 18, we collected blood and submandibular lymph nodes (LN) of the immunized ear to perform a histochemical analysis, and to measure the plasma immunoglobulins and cytokines. Results: The NC/Nga mice immunized with mite Ag suffered from AD-like skin lesions including erythema followed by edema, excoriation and scaling. The histological and immunohistochemical examinations of the affected skin showed epidermal hyperplasia with hyperkeratosis, severe infiltration of CD4+ T lymphocytes, eosinophils and macrophages, and degranulation of mast cells. The total plasma IgE level was markedly elevated in mite Ag-treated mice. LN cells of mice immunized with mite Ag synthesized IgE in an Ag-dependent manner and secreted interleukin-4 (IL-4) and IL-5 but not interferon-γ. Conclusions: NC/Nga mice treated with mite Ag manifest clinical and immunological aspects similar to patients with AD, suggesting that this model is suitable for exploring the pathogenesis of human AD.

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Background: FK506 ointment (tacrolimus ointment, protopic) is a new drug therapeutically effective for patients with atopic dermatitis (AD). However, the mechanism of action of FK506 ointment on AD is not fully understood. Methods: We examined the effect of FK506 ointment on mite antigen-induced dermatitis in NC/Nga mice. Clinical symptoms and ear thickness were recorded, and histopathological studies and in vitro analyses were performed. Results: Topical application of FK506 ointment (0.03–0.3%) suppressed the development of dermatitis. In the lesional skin, both interleukin (IL)-4 and interferon (IFN)-γ were detected, even though the IL-4+/IFN-γ– T helper 2 (Th2) population was predominant in the regional lymph nodes (LNs). Topical application of FK506 treatment reduced the elevated level of both IL-4 and IFN-γ in the skin, but did not decrease the expansion of the Th2 population in the LNs. Conclusions: Topical application of FK506 ointment suppresses dermatitis by inhibiting the activation of inflammatory cells locally, without systemic immune suppression, in this AD model.