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: | G Sellge † S Laffer‡ C Mierke§ S Vrtala‡ M W Hoffmann¶ J Klempnauer¶ M P Manns R Valenta‡ S C Bischoff |
| |
Institution: | Department of Gastroenterology, Hepatology and Endocrinology, Hannover, Germany. |
| |
Abstract: | 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 Fcgamma 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 Fcgamma receptors. CONCLUSION: This assay represents a new tool for the in vitro study of MC activation in response to natural and genetically modified allergens. Fcepsilon receptor I supercross-linking by allergen-specific IgG Abs provides a possible new mechanism of IgG-dependent enhancement of type I allergic reactions. |
| |
Keywords: | allergy Bet v 1 birch pollen Fcɛ receptor I histamine human IgE IgG mast cells recombinant allergens |
|