FC-EPSILON-RI ON HUMAN EPIDERMAL LANGERHANS CELLS - AN OLD RECEPTOR WITH NEW STRUCTURE AND FUNCTIONS

Structural and functional analysis of the high-affinity receptor for I gE (Fc epsilon RI) on Langerhans cells (LCs) has highlighted new aspec ts of the biology of this structure when expressed on antigen-presenti ng cells. In contrast to effector cells of anaphylaxis i.e. basophils and mast cells, where Fc epsilon RI is a tetrameric structure constitu tively expressed at high levels, this receptor on LCs lacks the classi cal beta-chain and its expression varies depending on the donor and th e inflammatory environment of the cells in the skin. Although the sign alling pathway seems to be similar to that of basophils or mast cells, only LCs from individuals with atopic dermatitis are fully activated by receptor ligation while LCs from normal individuals fail to exhibit calcium mobilization. LCs from normal and atopic individuals use Fc e psilon RI to maximise antigen uptake via specific IgE and subsequent p resentation to T cells and may be responsible for driving the T cell r esponse in either Th1, Th1 or Th2 type.