Immunohistopathological Analysis of Immunoglobulin E-Positive Epidermal Dendritic Cells with House Dust Mite Antigens in Naturally Occurring Skin Lesions of Adult and Elderly Patients with Atopic Dermatitis

The immunopathogenic role of house dust mite (HDM) allergens in the development of skin lesions in atopic dermatitis (AD) has not yet been precisely clarified. We immunohistopathologically evaluated the localization of immunoglobulin E (IgE)-positive epidermal dendritic cells with HDM antigens in the skin lesions of patients with IgE-allergic AD. Using double-immunofluorescence and single-immunochemical staining methods, we analyzed biopsy specimens from the skin lesions of six patients with IgE-allergic AD and HDM allergy and 11 control subjects with inflammatory skin disorders. Inflammatory dendritic epidermal cells (IDECs; CD11c+ and CD206+ cells) were markedly observed in the central area of the spongiotic epidermis of skin lesions in all AD patients. Furthermore, IgE-positive IDECs with HDM antigens in the central areas of the spongiosis were found in four of the six (66.7%) AD patients. Langerhans cells (LCs; CD207+ cells) with HDM antigens were also observed in the peripheral areas of the spongiosis. Infiltration of CD4+ and CD8+ T cells in association with IgE-positive IDECs and LCs with HDM antigens was seen in the spongiotic epidermis. An IgE-mediated delayed-type hypersensitivity reaction, in combination with IgE-bearing dendritic cells, specific T cells, keratinocytes, and HDM antigens, may lead to spongiotic tissue formation in eczematous dermatitis in AD.

The Origin and Function of Langerin (CD207) Expressing Cells in Mice and Humans

Abstract SCI-7 The current paradigm suggests that Langerhans cell histiocytosis (LCH) results from an accumulation of epidermal dendritic cells also called Langerhans cells. This concept is based on phenotypic and ultrastructural observations showing that LCH lesions are infiltrated by CD1a+langerin+ cells, two features thought to be restricted to epidermal Langerhans cells. It has been difficult, however, to understand how Langerhans cells, which are normally restricted to stratified epithelia, could give rise to such a multifocal disorder. LCH research has been handicapped by the inability to develop reliable animal models and by the fact that for a long time very few markers were available to determine the origin and stage of differentiation of histiocytes, now renamed macrophage/dendritic cell lineages. This presentation will discuss recent progress in our understanding of the regulation of the Langerhans cell, macrophage, and dendritic cell lineages and discuss the relationship of these lineages with the LCH cell. Disclosures: No relevant conflicts of interest to declare.