Crystal structure of the human high-affinity IgE receptor

Allergic responses result from the activation of mast cells by the human hi gh-affinity IgE receptor. IgE-mediated allergic reactions may develop to a variety of environmental compounds, but the initiation of a response requir es the binding of IgE to its high-affinity receptor. We have solved the X-r ay crystal structure of the antibody-binding domains of the human IgE recep tor at 2.4 Angstrom resolution. The structure reveals a highly bent arrange ment of immunoglobulin domains that form an extended convex surface of inte raction with IgE. A prominent loop that confers specificity for IgE molecul es extends from the receptor surface near an unusual arrangement of four ex posed tryptophans. The crystal structure of the IgE receptor provides a fou ndation for the development of new therapeutic approaches to allergy treatm ent.