REGULATION OF THE HIGH-AFFINITY RECEPTOR FOR IGE ON HUMAN EPIDERMAL LANGERHANS CELLS

Human epidermal Langerhans cells (LI) express variable amounts of the high affinity receptor for IgE (Fc epsilon RI); the strongest expressi on is characteristic of atopic dermatitis. The receptor is suggested t o take part in the pathophysiology of this disease by acting as a link between aeroallergens and Ag-specific T cells in an IgE-mediated, del ayed-type hypersensitivity reaction. In the present study we show that even in the absence of surface expression, normal LC maintain an intr acellular pool of the alpha-chain of Fc epsilon RI (Fc epsilon RI alph a) of the same m.w. as the surface-bound Fc epsilon RI alpha that is a ble to bind significant amounts of IgE. The lack of surface expression is linked to the absence or very low expression of the gamma-chain (F c epsilon RI gamma). Moreover, the amount of Fc epsilon RI alpha expre ssed at the cell surface significantly correlates with the amount of F c epsilon RI gamma. LC differentiation toward lymphoid dendritic cells is accompanied by the disappearance of transcripts for Fc epsilon RI alpha, but not for Fc epsilon RI gamma. This leads to a rapid decrease in the intracellular and surface Levels of Fc epsilon RI alpha, which cannot be influenced by IL-4, IgE, or other agents. Overall, our find ings suggest that these mechanisms enable LC to be highly versatile AP Cs by rapidly adapting the surface level of Fc epsilon RI to distinct inflammatory environments.