IgE-mediated rat mast cell triggering with tryptic and synthetic peptides of bovine β-lactoglobulin

Background: Immunoglobulin E (IgE) epitopes of beta-lactoglubulin (beta LG) have been identified by ELISA inhibition methods using sera from allergic patients. However, the functional capacity of these epitopes to stimulate mast cells is unknown. It is the goal of the present study to identify bivalent IgE epitopes of beta LG able to trigger target mast cells. Methods: Peptides were obtained either by purification from tryptic hydrolysates of beta LG or by synthesis. They were examined for their triggering activity in vitro on peritoneal H-3-serotonin- labeled rat mast cells passively sensitized with IgE anti-beta LG antibodies. In vivo, rats immunized with beta LG were administered peptides by gavage for intestinal rat mast cell protease II release. Results: Compared with intact beta LG, purified or synthetic tryptic-like beta LG peptides have a sharply decreased allergenicity. Peptide 149-162 retains the highest bivalent IgE epitope-mediated triggering capacity. Conclusion: A functional bivalent IgE epitope was identified at the C terminal end of beta LG. Copyright (C) 2005 S. Karger AG, Basel.