Inhibition of passive sensitization of human peripheral basophils by synthetic human immunoglobulin E peptide fragments

Abstract

To delineate the binding site in the human immunoglobulin E (IgE) molecule to the Fcϵ receptor on basophils and mast cells, we chemically synthesized a total of 71 peptide fragments within the sequence Ser 300-Lys 547 in the human IgE molecule. The synthetic peptides were tested for their capacity to inhibit passive sensitization of human peripheral basophils with atopic patient's serum containing the specific IgE against dust mites in vitro. It was found that a peptide fragment, Pro 345-Ile 356, potently inhibited the passive sensitization. To clarify the minimal active core, various analogues, such as shortened, substituted (by Gly or Ala residue), omission and retro-sequence peptides, were synthesized and assayed. The results suggested that the sequence Pro 345-Lys 352 in the human IgE molecule would be an IgE binding site, and that a synthetic octapeptide, Pro 345-Phe-Asp-Leu-Phe-Ile-Arg-Lys 352, inhibited the passive sensitization, probably by occupying the Fcϵ receptor sites on the cells.