Receptor phage. Display of functional domains of the human high affinity IgE receptor on the M13 phage surface

In this paper we demonstrate that phage display technology is a suitable system for studying the interaction between the high-affinity receptor for IgE (Fc epsilon RI) and IgE. The alpha subunit extracellular domains of the human receptor were expressed on the surface of filamentous phage M13 fused to the carboxyl-terminal part of the gene III protein (pIII). Two constructs were made, the first with both the Ig-like domains of the receptor alpha chain and the second with only the C-terminal domain. The fusion genes were cloned in a phagemid vector to display monovalently the receptor on the phage surface. Our results indicate that the alpha receptor expressed on the phage is able to interact with IgE as demonstrated by an ELISA assay. In addition, by using the same system, we show that a single domain of the alpha receptor is sufficient for the interaction with IgE although with a binding affinity lower than that of the two-domain receptor.