Wheat allergy (1)

Wheat is the most widely consumed food grain in the　world. Wheat allergy is defined as an adverse immunologic reaction to wheat. Depending on the route of allergen exposure and the underlying immunologic mechanisms, wheat allergy is classified into classic food allergy affecting the skin, gastrointestinal tract, or respir- atory tract; food-dependent, exercise-induced anaphylaxis (FDEIA); occupational asthma (so-called baker’s asthma) and rhinitis; or contact urticaria. In addition, ingestion of wheat gluten may cause celiac disease, T cell-mediated intestinal inflammation, or dermatitis herpetiformis, a blistering skin eruption. US Food and Drug Administration (FDA) reported the prevalence of the self-reported, doctor-diagnosed wheat allergy is 0.4%. Even though the gastrointestinal tract would be mature in adults and escape the absorption of wheat allergens without any triggers, various factors that could increase the permeability of the intestines might result in adult onset of food allergy or exacerbate allergic symptoms.

Wheat proteins are categorized into four fractions on the basis of their solubility in a series of solvents: water (albumins), dilute salt solutions (globulins), aqueous alcohol (gliadins), and dilute alkali or acid (glutelins). In water/salt-insoluble gluten named gliadins, w-5 gliadin was identified as a major allergen of wheat dependent, exercise-induced anaphylaxis (WDEIA). Four of seven B-cell epitopes of w-5 gliadin identified in WDEIA (QQIPQQQ, QQFPQQQ, QQSPEQQ, and QQSPQQQ) were found to be dominant. Glutenins in the water/salt-insoluble fraction are poly- meric proteins made up of subunits of HMW and low molecular weight (LMW). Three B-cell epitopes of HMW glutenin subunits from repetitive domains, QQPGQ, QQPGQGQQ, and QQSGQSGQ, were identified.

The sensitivities of the allergen-specific IgE tests for recombinant (r) v-5 gliadin (rv-5 gliadin) (80%) by the ImmunoCAP system were higher than those of wheat (48%), gluten (56%), and B-cell epitope peptides of wheat w-5 gliadin (76%) and HMW glutenin (22%). The biological activity of wheat allergens such as a new in-vitro mast cell degranulation assay and in-vivo SPT with purified and recombinant wheat allergen were reported.

1. N. Inomata, Wheat allergy. Curr. Opin. Allergy Clin. Immunol. 9, 238–243 (2009).