In vivo Modulation of the High-Affinity Receptor for IgE (FcεRI) on Human Epidermal Langerhans Cells.

The presence of IgE-bearing epidermal Langerhans cells (LC) has been reported not only in patients with atopic eczema (AE) but also in patients with various inflammatory dermatoses unrelated to atopic diathesis. We have shown very recently that normal LC express the high-affinity receptor for IgE (FcεRI) which accounts for the binding of monomeric IgE on these cells. In the present study, we investigated the IgE-binding capacity of resident LC on cryosections from skin of normal individuals and from uninvolved and involved skin of patients with atopic eczema, psoriasis, lupus erythematosus and mycosis fungoides. When compared to LC from uninvolved or normal skin, an increased binding of IgE was observed in LC from lesional skin of all four diseases studied here. This binding could be blocked by anti-FcεRI mAb. Furthermore, increased IgE binding capacity of LC correlated to an increased expression of FcεRI on these cells. These results clearly demonstrate that the expression of FcεRI on LC is increased in inflammatory skin areas. Since this phenomenon is observed in several unrelated diseases, it suggests the presence in these conditions of a similar microenvironment which up-regulates the FcεRI expression on LC.