Expression of Fc receptors for IgG during acute and chronic cutaneous inflammation in atopic dermatitis

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Abstract
Atopic dermatitis is an allergic skin disease characterized by elevated total and antigen-specific serum IgE and IgG4 levels. In acute and chronic cutaneous inflammation, large cellular infiltrates including T cells, dendritic cells and macrophages are found, especially in the dermis. These cells play an important part in the regulation of local inflammatory reactions. Receptors binding IgG (FcgammaR) are involved in dendritic cell and macrophage function. In this study, we examined the in vivo distribution and cellular expression of the three classes of leucocyte FcgammaR in human skin during acute and chronic cutaneous inflammation in atopic dermatitis. Atopy patch test skin was used as a model for acute inflammation in atopic dermatitis, while chronic lesional skin was used to investigate FcgammaR expression in chronically inflamed skin. In atopy patch test sites no increase in the number of CD1a+ dendritic cells and a slight increase in macrophages compared with non-lesional skin was observed. Our results showed increased expression of FcgammaRI (CD64) and FcgammaRIII (CD16) in acutely inflamed skin as well as in chronically inflamed lesional skin, compared with healthy and non-lesional atopic dermatitis skin. FcgammaRI was expressed by RFD1+, RFD7+ and CD68+, but not by CD1a+ dermal dendritic cells. RFD1+ dendritic cells and CD68+ macrophages were the main FcgammaRIII-expressing cells during the acute inflammatory reaction. The significant increase in expression of FcgammaRIII (CD16) and FcgammaRI (CD64) probably results from upregulation of the receptors on resident cells. Insight into the presence of FcgammaR+ cells in human skin during inflammation is important both for our understanding of skin immune reactions and the development of new therapeutic concepts.