New insights in the structure and biology of the high affinity receptor for IgE (FcϵRI) on human epidermal Langerhans cells

Abstract

The recent structural and functional analysis of the high affinity receptor for IgE (FcϵRI) expressed on human epidermal Langerhans cells (LC) revealed new aspects of the biology of this structure. In contrast to basophils and mast cells where this receptor seems to be expressed constitutively at a constant level, the expression of FcϵRI on LC varies on the donor and the inflammatory environment of the cells and lacks the classical β-chain. This also implies functional differences most probably related to the expression level. Although the signalling pathway seems to be similar to that of basophils or mast cells, LC from individuals with atopic dermatitis are fully activated by receptor ligation while LC from normal individuals fail to exhibit calcium mobilization under the same conditions. Finally, LC from normal and atopic individuals use FcϵRI to maximize antigen uptake via specific IgE and subsequent presentation to T cells. Thus, FcϵRI expressed on LC differs in terms of structure and function from that expressed on effector cells of anaphylaxis.