The presence of IgE molecules on epidermal Langerhans cells in atopic dermatitis and their significance for its pathogenesis

Abstract

Aeroallergens can induce a delayed patch test reaction, which is specific for patients with atopic dermatitis (AD). Histopathology of this aeroallergen induced skin reaction suggests the involvement of Langerhans cells (LC), T cells and eosinophils. Since LC from AD patients may bear Fc sigma, R-bound IgE molecules, it was hypothesized that aeroallergens after contact with the skin bind to allergen-specific IgE on LC leading to efficient presentation to T cells. In vitro studies show that LC from AD patients can indeed present aeroallergens to T cells, provided LC-bound IgE molecules are present. These results, firstly, explain the reaction mechanism behind the patch test reaction to aeroallergens; secondly, they point to a new allergic reaction mechanism in which a link is provided between type I and type IV allergic reactions according to Gell and Coombs; thirdly, they throw a new light on the role of aeroallergens in the pathogenesis of AD. Aeroallergens may after contact with skin of AD patients not only induce eczematous skin lesions but also be involved in the induction of the synthesis of allergen specific IgE molecules. From a practical point of view, the results of this study show that aeroallergens play a more important role in the pathogenesis of AD than has been accepted so far.