Molecular Diagnosis in Pediatric Allergy

The advent of molecular biology has had a great impact on our understanding of IgE-mediated allergic diseases. In particular, new tests have been developed for in vitro diagnostics of respiratory and food allergies, some of which specifically suited to the pediatric age. In this chapter, we first review the most important basic concepts and definitions of molecular allergology; then, we specifically talk about molecular advances in diagnostics of allergic rhinitis and asthma and of atopic dermatitis and other diseases associated with allergic reactions to foods. After having discussed how IgE and allergen molecules interact on the surface of degranulating cells (basophils, mast cells), we present the evolution of total IgE levels and of specific IgE responses in childhood. In particular, we describe how the IgE response expands from one to more molecules of the same allergen source and discuss how this observation has modified our understanding of immunological intervention, pointing our attention on earlier diagnosis, immunotherapy, and even allergen-specific immunoprophylaxis. We also give some examples of how molecular IgE tests not only address biomarkers of specific phenotypes of allergic rhinitis, disease severity, and comorbidities (oral allergy syndrome, asthma) but also how they help in the identification of the culprit allergen for a more precise prescription of allergen immunotherapy. Then, we present the evolution of IgE responses to food allergens in childhood, and we illustrate the biomarkers of primary food allergy and other molecules, associated with less severe allergic reactions. Last, we focus on the trends of IgE antibody levels during spontaneous resolution of food allergy and on the role of IgG4 antibodies in accompanying this process.