Evaluation of an in vitro Mast Cell Degranulation Test in the Context of Food Allergy to Wheat

Abstract

Background: Antigenic profiles obtained by ELISA with IgE from patients with wheat food allergy (WFA) established that major allergens are albumins/globulins (AG) for children suffering from atopic eczema/dermatitis syndrome (AEDS), ω5-gliadins for adults suffering from wheat-dependent exercise-induced anaphylaxis (WDEIA), anaphylaxis or urticaria and low-molecular-weight (LMW) glutenin subunits for patients with anaphylaxis. We aimed to characterize a new mast cell transfectant for its ability to degranulate with wheat proteins and patient sera and compare these results to those obtained by ELISA. Methods: Thirty sera from patients with WFA were tested: 14 with AEDS (group 1) and 16 with WDEIA, anaphylaxis or urticaria (group 2). An IgE Fc receptor (FcΕRI) humanized rat RBL-2H3 line was established by transfection with cDNAs encoding α-, β- and γ-subunits for the human IgE receptor. Results: A humanized RBL clone was selected for its capacity to express mRNA α-, β- and γ-subunits of FcΕRI, to bind allergen-specific human IgE and to degranulate. In group 1, sera induced enhanced degranulation with AG extract, but rarely reacted with gliadins and glutenins. In group 2, half of the sera showed degranulation with LMW glutenins whereas the AG fraction and lipid transfer proteins were rarely positive. ω5-Gliadins did not appear as a major allergen in degranulation assays, although functional allergen-specific IgE was measurable in appreciable amounts. Conclusion: Our data demonstrate that in wheat food allergen evaluation, correlation exists between mast cell degranulation and IgE measurements, depending on the type of allergen. Therefore, the biological activity of some allergen types may also be affected by other parameters.

Low Molecular Weight Glutenins in Wheat-Dependant, Exercise-Induced Anaphylaxis: Allergenicity and Antigenic Relationships with Omega 5-Gliadins

“…However, the clinical relevance of this reactivity was not clear because no wheat-allergic patients were monosensitized to these proteins. In the same way, mast cell degranulation assays [16] have detected LMW-GS as major reacting proteins for a group of patients suffering from WDEIA, urticaria and anaphylaxis, whereas ω5-gliadins were not. The authors hypothesized that ω5-gliadins would have to be modified by transglutaminase to develop their immunogenicity.…”

“…It is interesting to note that, while ω5-gliadins and LMW-GS were both detected by ELISA and immunoblotting as major IgE-reacting proteins in WDEIA, this was not the case when an in vitro mast cell degranulation test was used. LMW-GS generated a degranulation process but ω5-gliadins did not [16]. This result emphasizes the differences of reactivity of these two kinds of prolamins with cells involved in the immune response.…”

Degradation of Wheat Epitope Peptides for Atopic Dermatitis and Exercise-Induced Anaphylaxis by Microbial Proteases

“…Due to the lower degradation of QQQPP, degradation of a longer peptide, including QQQPP, was examined. Since an allergenic 30-mer peptide, (SQQQQPPFSQQQPPF) 2 , was isolated from the enzymatic hydrolysate of gluten 15 , a synthetic 16-mer peptide Glu-16 was designed for the reaction. The N-terminal C residue of Glu-16 was added for identification of partially degraded peptides.…”

“…The cross-linking of a peptide and multiple molecule of IgE is necessary for the degranulation of rat basophilic leukemia cells 2,6 . The partially degraded peptides of QPPFSQQQPP and SQQQPPF from Glu-16 were unable to bind to multiple molecules of IgE from wheat allergy patients, because the peptides contained only one epitope.…”

“…10,11 . Food allergy is generally caused by a cross-linking of allergens and human immunoglobulin E (IgE), and degranulation of mast cells 2,6 . The granules from mast cells contain inflammatory substances such as histamines.…”