Clinical & Experimental Allergy

Development of an in vitro system for the study of allergens and allergen-specific immunoglobulin E and immunoglobulin G: Fcɛ receptor I supercross-linking is a possible new mechanism of immunoglobulin G-dependent enhancement of type I allergic reactions

Authors


Stephan C. Bischoff, University of Hohenheim, Chair of Nutritional Medicine and Immunology, Fruwirthstr. 12, D-70593 Stuttgart, Germany.
E-mail: bischoff.stephan@uni-hohenheim.de

Summary

Background IgE-dependent activation of mast cells (MCs) is a key pathomechanism of type I allergies. In contrast, allergen-specific IgG Abs are thought to attenuate immediate allergic reactions by blocking IgE binding and by cross-linking the inhibitory Fcγ receptor IIB on MCs.

Objectives To establish a defined in vitro system using human MCs to study the biological activity of allergens and to investigate the role of allergen-specific IgE and IgG.

Methods Purified human intestinal MCs sensitized with different forms of specific IgE Abs were triggered by monomeric and oligomeric forms of recombinant Bet v 1, the major birch pollen allergen, in the presence or absence of allergen-specific IgG Abs.

Results MCs sensitized with an anti-Bet v 1 IgE mAb or sera obtained from birch pollen allergic patients released histamine and sulphidoleukotrienes after exposure to oligomeric Bet v 1. Monomeric Bet v 1 provoked mediator release only in MCs sensitized with patients sera but not in MCs sensitized with anti-Bet v 1 IgE mAb. Interestingly, MC activation could be induced by supercross-linking of monomeric Bet v 1 bound to monovalent IgE on MCs with a secondary allergen-specific IgG pAb. By using IgG F(ab′)2 fragments we provide evidence that this effect is not a result of IgG binding to Fcγ receptors.

Conclusion This assay represents a new tool for the in vitro study of MC activation in response to natural and genetically modified allergens. Fcɛ receptor I supercross-linking by allergen-specific IgG Abs provides a possible new mechanism of IgG-dependent enhancement of type I allergic reactions.

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