The human mast cell receptor binding site maps to the third constant domain of immunoglobulin E

Abstract

The characterization of the site on the IgE molecule which accommodates the high affinity receptor for IgE (Fcϵ RI) should allow the design of IgE analogues which can be utilized to block allergic responses. Using chimeric human IgE molecules in which different constant region domains were exchanged with their murine homologues, we demonstrate here that the Cϵ3 in its native configuration is essential for the binding to the α subunit of the human FcϵRI. Deletion of the human Cϵ2 from such chimeric molecules did not impair their ability to interact with the FcϵRI, indicating that Cϵ2 is not directly involved in the human FcϵRI binding site and that Cϵ3 alone is necessary and sufficient to account for most of the human Fcϵ RI-binding capacity.