ROLE OF COMPLEX ASPARAGINE-LINKED GLYCANS IN THE ALLERGENICITY OF PLANT GLYCOPROTEINS

Many plant proteins, particularly those found in foods and pollen, are known to act as sensitizing agents in humans upon repeated exposure, Among the cereal flour proteins involved in asthmatic reactions, those members of the a-amylase inhibitor family which are glycosylated, pol ypeptides BMAI-1, BTAI-CMb, and WTAI-CM16* are particularly reactive both in vivo and in vitro, We show here that these major glycoprotein allergens carry a single asparagine-linked complex glycan that contain s both beta 1 --> 2 xylose and alpha 1 --> 3 fucose, Evidence is prese nted that the xylosyl residue and, to a lesser extent, the fucosyl res idue are key IgE-binding epitopes and largely responsible for the alle rgenicity of these and unrelated proteins from plants and insects, Our results suggest that the involvement of xylose- and fucose-containing complex glycans in allergenic responses may have been underestimated previously; these glycans provide a structural basis to help explain t he cross-reactivities often observed between pollen, vegetable food, a nd insect allergens.