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

ABSTRACT: BACKGROUND:The low-affinity receptor for IgE, Fc?RII (CD23), contributes to allergic inflammation through allergen presentation to T cells, regulation of IgE responses, and enhancement of transepithelial allergen migration. OBJECTIVE:We sought to investigate the interaction between CD23, chimeric monoclonal human IgE, and the corresponding birch pollen allergen Bet v 1 at a molecular level. METHODS:We expressed 4 CD23 variants. One variant comprised the full extracellular portion of CD23, including the stalk and head domain; 1 variant was identical with the first, except for an amino acid exchange in the stalk region abolishing the N-linked glycosylation site; and 2 variants represented the head domain, 1 complete and 1 truncated. The 4 CD23 variants were purified as monomeric and structurally folded proteins, as demonstrated by gel filtration and circular dichroism. By using a human IgE mAb, the corresponding allergen Bet v 1, and a panel of antibodies specific for peptides spanning the CD23 surface, both binding and inhibition assays and negative stain electron microscopy were performed. RESULTS:A 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 with glycosylated CD23. Furthermore, we demonstrated that a therapeutic anti-IgE antibody, omalizumab, which inhibits IgE binding to Fc?RI, also inhibited IgE binding to CD23. CONCLUSION:Our 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.

SUBMITTER: Selb R 

PROVIDER: S-EPMC5321597 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature