Allergenicity of plant and invertebrate N-
glycans has been shown to be caused by the presence of two typical nonmammalian substitutions: an alpha(1,3)-fucose linked to the proximal
N-acetylglucosamine and a beta(1,2)-xylose linked to the core
mannose.
IgE antibodies against these
carbohydrate structures are induced upon exposure to pollen or after
insect stings, and result in extensive cross-reactivity to plant and invertebrate foods. These cross-reactive
IgE antibodies have been shown to possess variable degrees of
biological activity, but have never been convincingly shown to induce clinical
food allergy. The most likely explanation for this lack of clinical relevance has to be sought in a combination of
epitope valency and antibody affinity. In diagnostic tests, these
antibodies are at the basis of many false-positive test results for
food allergy. Recombinant technologies offer the possibility to produce
allergens that do not carry
IgE-binding
glycans. Whether their absence or presence is of importance for the application of recombinant
allergens in
immunotherapy is still largely unknown.