Peptide inhibition of the Prausnitz-Küstner reaction.

A pentapeptide was synthesized with the same amino acid sequence that occurs in a unique region of the chaim of immunoglobulin E near the cysteine residue participating in the linkage between the two heavy chains. This pentapeptide has the capacity to block a standard Prausnitz-Küstner reaction as well as to inhibit a known positive skin test reaction. Other similar synthetic polypeptides had less or no inhibitory activity. The likelihood that this pentapeptide amino acid sequence does in fact represent the structure of the specific immunoglobulin E binding site for the mast cell and basophil is considered.