[PMC free article] [PubMed] [Google Scholar] 73. be a promising approach to gain more insight into the allergic reaction and to improve serum\based allergy diagnostics. Keywords: B\cell epitopes, epitope mapping, food allergy, monoclonal antibodies 1.?INTRODUCTION Food allergy is currently diagnosed by careful history, food challenges, skin prick test (SPT), and measurement of specific IgE (sIgE). The double\blind placebo\controlled food challenge (DBPCFC) is the gold standard, but is a costly and burdensome procedure. Both SPT and sIgE measurement, using entire foods or single allergenic components, are hampered by false\positive test outcomes.1 This might be related to the presence of BIX-02565 both clinically relevant and irrelevant antibodies as it has been shown for serum\based diagnostics of anti\neutrophilic cytoplasmic antibody\associated vasculitis.2 Serum\based measurement might be improved by defining the epitope specificity, affinity, critical amino acids, and antibody isotypes relevant for allergy. Extensive research has been carried out, especially for peanut3, 4, 5, 6, 7, 8, 9, 10 and cow’s milk,11, 12, 13, 14, 15, 16 to identify the IgE and IgG4 epitopes of food allergens. Linear epitopes, composed of a continuous amino acid sequence, have been detected by screening patient sera on sequential overlapping peptide libraries or allergen fragments. Conformational epitopes, composed of sterically closed amino acids upon folding, were characterized by phage display technique or mass spectrometry partly in Rabbit Polyclonal to CNKR2 combination with B\cell epitope prediction web tools or software, although the use of these techniques still has to be proven in future studies.6, 17, 18, 19, 20, 21 So far, it is impossible to discriminate between clinically relevant and irrelevant epitopes or combinations using current approaches and to BIX-02565 use these differences as diagnostic or prognostic markers. This review will discuss current knowledge, based on a relatively small number of studies investigating linear as well as conformational epitopes and comparing allergic and tolerant patients, and will propose alternative approaches for epitope mapping, focussing on epitope specificity and how this might impact serum\based allergy diagnostics. 2.?REQUIREMENTS FOR EFFECTOR CELL DEGRANULATION BY FcRI CROSS\LINKING The major requirement for degranulation is the cross\linking of at least two FcRI receptors. Cross\linking will only be feasible if two FcRI receptors are spaced apart by 50\240??. This range has been defined BIX-02565 by using artificial allergens and hence might be somewhat smaller or larger for native allergens.22, 23, 24 Consequently, the distance of two functional IgE epitopes within one combination is restricted to the required distance BIX-02565 of two FcRI receptors. As an example, possible IgE epitope combinations of Ara h 2.0201, based on a 3D model built with the SWISS\MODEL web portal, are shown in Figure?1.25, 26, 27, 28, 29 Residue distances greater than 35??, calculated with Chimera,30 were considered as functional epitope combinations, highlighted on the 3D structure using Schr?dinger Release 2018\1 (Maestro, Schr?dinger, LLC, New York, NY, 2018). Additionally, at least one epitope of the combination must be recognized with high affinity since the cross\linking has to take place for at least 100?seconds. Moreover, at least 1000 cross\links of FcRI receptors on the surface of one effector cell have to take place.31, 32, 33 If all these requirements for FcRI cross\linking are met, the extent of degranulation is regulated by sIgE concentration, affinity, the ratio of allergen sIgE antibodies BIX-02565 compared to total IgE, and the specificity and number of epitopes recognized.34 These requirements suggest that certain epitope/antibody combinations are only present in allergic and not in tolerant patients. However, basophils from 10% to 20% of the general population do not respond at all due to low expression of syk and/or SHIP\1 resulting in the inhibition of intracellular signalling.35, 36, 37, 38 Thus, different expression levels might regulate the extent.