Immunologic cross-eactivity is the binding of antibodies or activation of sensitized T-cells to similar antigens: proteins, carbohydrates, or glycoproteins which contain similar or identical determinants. The similarity may be based on sequential or conformational similarity. Most allergens, particularly allergens of plant origin, are glycoproteins, carrying (frequently) N-glycans and O-glycans. Due to their involvement in a wide spectrum of cross-reactivities, these N-glycans have been named "cross-reactive carbohydrate determinants" (CCD). In contrast to peptide epitopes, glycan epitopes may share significant structural elements with allergens of other, non-related protein families, whereby they induce IgE-cross-reactions between allergens from completely different sources, i.e. plant-derived pollen, natural rubber latex and insect venoms. The clinical relevance of CCDs is still controversial, and they seem to be responsible for decreased specificity of in vitro diagnostic test currently used for allergy diagnosis, which complicates the identification of the allergens responsible for a sometimes severe allergic reaction. Members of certain protein familiesmaycause cross-reactions, i.e. profilins, Bet-v-1-homologous proteins and lipid transfer proteins. Component-resolved diagnosis (CRD) using single allergens allow the molecule-specific detection of IgE. The significance of the results, however, has to be evaluated with regard to the source of allergen in question and with regard to the individual patient. CRD is based on purified natural or recombinant single allergens, which may contain cross-reactive peptide epitopes, as well. In general, the sensitivity of IgE detection increases, but not necessarily the diagnostic specificity. Diagnostic tests for allergy based on human cells indirectly detecting IgE-mediated sensitization are not superior to direct IgE-detection methods with regard to cross-reactivity, for example, via CCD, and are, therefore, indicated for allergy testing in selected cases only. The application of marker allergens, i.e. screening with CCDs and/or CCD-carrying allergens, and inhibition assays with a superior or at least relevant CCD-carrying allergen can help to decrease CCD interference in diagnostic tests of allergy. The well designed use of natural and recombinant allergens may additionally improve the specificity of IgE-detection.
|Translated title of the contribution||In vitro allergy diagnostic tests and cross-reactivity|
|Number of pages||9|
|Publication status||Published - 01.01.2010|