Critical and direct involvement of the CD23 stalk region in IgE binding

Publication date: Available online 7 May 2016
Source:Journal of Allergy and Clinical Immunology
Author(s): Regina Selb, Julia Eckl-Dorna, Teresa E. Twaroch, Christian Lupinek, Andrea Teufelberger, Gerhard Hofer, Margarete Focke-Tejkl, Barbara Gepp, Birgit Linhart, Heimo Breiteneder, Adolf Ellinger, Walter Keller, Kenneth H. Roux, Rudolf Valenta, Verena Niederberger
BackgroundThe low-affinity receptor for IgE, FcεRII (CD23), contributes to allergic inflammation by allergen presentation to T cells, regulation of IgE responses and enhancing trans-epithelial allergen migration.ObjectiveTo investigate the interaction between CD23, chimeric monoclonal human IgE and the corresponding birch pollen allergen, Bet v 1 at a molecular level.MethodsWe expressed four CD23 variants. One variant comprised the full extracellular portion of CD23 including stalk and head domain, one was identical with the first except of an amino acid exchange in the stalk region abolishing the N-linked glycosylation site, and two variants representing the head domain, one complete and one truncated. The four CD23 variants were purified as monomeric and structurally folded proteins as demonstrated by gel filtration and circular dichroism. Using a human monoclonal IgE antibody, the corresponding allergen Bet v 1 and a panel of antibodies specific for peptides spanning the CD23 surface, binding as well as inhibition assays and negative stain electron microscopy were performed.ResultsA hitherto unknown IgE binding site was mapped on the stalk region of CD23 and the non-N-glycosylated monomeric version of CD23 was superior in IgE binding compared to glycosylated CD23. Furthermore, we demonstrated that a therapeutic anti-IgE antibody, omalizumab, which inhibits IgE binding to FcεRI, also inhibited IgE binding to CD23.ConclusionOur results provide a new model for the CD23-IgE interaction. We show that the stalk region of CD23 is crucially involved in IgE binding and that the interaction can be blocked by the therapeutic anti-IgE antibody omalizumab.

Teaser

We provide a new model of interaction between CD23 and IgE by showing a direct involvement of the CD23 stalk region in IgE binding. Furthermore, we demonstrate that a therapeutic anti-IgE antibody, omalizumab, blocks the binding of IgE to CD23.


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