Epidermal langerhans cells from normal human skin bind monomeric IgE via FcεRI

Abstract

Human epidermal Langerhans cells (LC) bearing IgE are found in disease states associated with hyperimmunoglobulinemia E. When studying the mechanism(s) underlying this phenomenon, immunohistology revealed that a majority of epidermal LC from normal skin of healthy individuals can specifically bind monomeric IgE. IgE binding to LC could neither be prevented by preincubation of the tissue with monoclonal antibodies (mAb) against either FcεRII/CD23 or FcγRII/CD32, nor by the addition of lactose. However, binding could be entirely abrogated by preincubation with the anti-FcεRIα mAb 15-1, which interferes with IgE binding to FcεRIαγ transfectants. These observations indicated that IgE binding to epidermal LC is mediated by FcεRI rather than by CD23, CD32, or the D-galactose-specific IgE-binding protein. This assumption gained support from our additional findings that: (a) the majority of LC exhibited distinct surface immunolabeling with the anti-FcεRIα mAbs 15-1 and 19-1, but not with any of eight different anti-FcεRII/CD23 mAbs; and (b) transcripts for the α, β, and γ chains of FcεRI could be amplified by polymerase chain reaction from RNA preparations of LC-enriched, but not of LC-depleted, epidermal cell suspensions. In view of the preeminent role of FcεRI crosslinking on mast cells and basophils in triggering the synthesis and release of mediators of allergic reactions, the demonstration of this receptor on epidermal LC may have important implications for our understanding of allergic reactions after epicutaneous contact with allergens.