Fucose alpha 1,3-linked to the core region of glycoprotein N-glycans creates an important epitope for IgE from honeybee venom allergic individuals.

The reactivity of sera from honeybee venom allergic patients with the N-glycan of phospholipase A2 was investigated using neoglycoproteins with an enzyme-linked immunosorbent assay. Of 122 sera with appreciable levels of IgE antibodies directed against bee venom as measured by radioallergosorbent test, 34 sera exhibited significant amounts of glycan-reactive IgE. These sera cross-reacted with the N-glycan from the plant glycoprotein bromelain. The interaction of IgE with the N-glycan from phospholipase could be inhibited with glycopeptides from bromelain which shares the alpha 1,3-fucosylation of the asparagine-bound N-acetylglucosamine with bee venom phospholipase. Since defucosylated bromelain glycopeptides or glycopeptides containing a Man3GlcNAc2 oligosaccharide were not recognized by most of these sera, we conclude that alpha 1,3-fucosylation of the innermost N-acetylglucosamine residue of N-glycoproteins forms an IgE-reactive determinant. This structural element is frequent in glycoproteins from plants, and it occurs also in insects. It is suspected to be one of the major causes of the broad allergenic cross-reactivity among various allergens from insects and plants.