Several distinct properties of the IgE repertoire determine effector cell degranulation in response to allergen challenge

Department of Experimental Immunology, ALK-Abelló A/S, Hørsholm, Denmark.
The Journal of allergy and clinical immunology (Impact Factor: 11.25). 07/2008; 122(2):298-304. DOI: 10.1016/j.jaci.2008.05.026
Source: PubMed

ABSTRACT On cross-linking of receptor-bound IgE antibodies by allergens, effector cells (basophils and mast cells) involved in type I allergic reactions degranulate and release the potent chemical mediators stored inside their granules. Total and allergen-specific IgE concentrations, IgE affinity for allergen, and IgE clonality are all distinct properties of allergic patients' IgE repertoires. However, the inability to isolate individual IgE antibodies from allergic patients' sera presents a major barrier to understanding the importance of patient-specific IgE repertoires for the manifestation and severity of allergic symptoms.
We sought to investigate how individual properties of an IgE repertoire affect effector cell degranulation.
A panel of recombinant IgE (rIgE) antibodies specific for the major house dust mite allergen Der p 2 was developed and characterized in regard to Der p 2 affinity, as well as Der p 2 epitope specificity, by using surface plasmon resonance technology. Human basophils were sensitized with different combinations of rIgEs, and degranulation responses were measured by means of flow cytometry after challenge with Der p 2.
A total of 31 Der p 2-specific rIgEs were produced. They bound a total of 9 different Der p 2 epitopes in the affinity range (K(D) value) of 0.0358 to 291 nM. Factors increasing human basophil degranulation were increased total IgE concentrations, increased concentrations of allergen-specific IgE relative to non-allergen-specific IgE, more even concentration of individual allergen-specific IgE clones, increased IgE affinity for allergen, and increased number of allergen epitopes recognized by the IgE repertoire (increased IgE clonality).
This study demonstrates how distinct properties of the IgE repertoire, such as total and allergen-specific IgE antibody concentration, IgE affinity, and IgE clonality, affect effector cell degranulation.

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Available from: Lars Harder Christensen, Aug 04, 2014
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    • "Also El-Khouly et al. (2007) showed that IgE avidity to Ara h 2 correlated with the severity of peanut allergic patients. These studies are confirmed by cellular assays showing that basophilic responses were highly affected by IgE antibody affinity (Christensen et al., 2008, 2010; Mita et al., 2000). For IgG4, that is even more scarcely described, it has been shown that an increased affinity of specific IgG4 antibodies could be associated with less symptoms and the development of tolerance . "
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    • "The results showed that the complex is in fast exchange regime, since Art v 1 was in 25-fold molar excess to IgE (2 mM IgE and 50 mM Art v 1). A broad range of IgE affinities (0.0358–291 nM) has been previously reported using a repertoire of recombinant IgE antibodies specific for the major house dust mite allergen (Christensen et al., 2008). This study convincingly demonstrated that, in the presence of single high affinity IgE, medium to low affinity antibodies can efficiently cause crosslinking and effector cell degranulation. "
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    • "However, the information about conformational epitopes, which are of great importance in highly resistant proteins such as nsLTPs, would be lost due to the own limitation of the technique. The inherent restrictions of this approach suggest that potentially relevant IgE-binding regions of the allergen studied, particularly conformational epitopes formed by sequentially discontinuous amino acid residues, cannot be detected (Aalberse, 2000; Christensen et al., 2008). The production of hypoallergenic forms has been used to analyze structural epitopes. "
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