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Wise et al.

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sensitization to a cross-reactive component. 1013 Measuring sensitization to individual allergen molecules in a CRD may more be informative than standard tests using whole allergen extracts. 470,1014-1016 Current multiplex CRD platforms allow the testing for component-specific IgE to more than 100 allergenic molecules in a single assay, and in a small volume of serum. 1013,1015 The patterns of component-specific IgE responses to multiple allergenic proteins have a reasonable discrimination ability for rhinoconjuinctivitis, 1017 and distinct patterns of IgE responses to different protein families are associated with different clinical symptoms. For example, sensitization to proteins of plant origin strongly predicts AR, and sensitization to animal lipocalins is predictive of asthma. 1018,1019 The risk of allergic disease increases with the increasing number of sensitizations to individual allergenic proteins, and IgE polysensitization to several HDM molecules strongly predicts rhinitis. 1019,1020 It is important to emphasize that the age of onset of sensitization is crucially important, and that development of AR may be predicted by the unique molecular nature of IgE responses to individual allergen components. 1019 Disaggregating atopic sensitization— It is becoming increasingly clear that “atopic sensitization” is not a single phenotype, but an umbrella term for several different atopic vulnerabilities which differ in their association with rhinitis and asthma. 1021,1022 Different subtypes of atopy are characterized by a unique pattern of the responses to different allergens and the timing of onset of allergen-specific sensitization. 1023 Translation of these findings into clinical practice requires the development of biomarkers which can differentiate between different subtypes of sensitization, and can be measured at the time of clinical evaluation. Beyond IgE— Recent data suggest that among individuals sensitized to grass pollen, the decreasing ratio of grass allergen-specific IgG/IgE antibodies is associated with increasing risk of symptomatic SAR, 1024 suggesting that the IgG/IgE ratio may help distinguish between “benign” sensitization (sensitization with no symptoms) and “pathologic” sensitization. 1024 However, the measurement of allergen-specific IgG cannot as yet be recommended in a routine clinical practice. 1009,1010 VIII.H.1. Allergen challenge chambers (ACCs)— Environmental exposure chambers (EECs) have been used for decades for controlled exposure of subjects to a well-defined atmosphere of a variety of substances such as allergens, particulate and gaseous air pollutants, chemicals, or climate conditions. The generation of valid exposure conditions with high temporal and spatial stability is technically demanding, and there are a limited number of EECs world-wide. Besides the opportunity to use EECs for well-designed mechanistic studies on the effect of environmental pollutants on human health, allergen challenge in the chamber setting with induction of symptoms in patients with allergic disease is an intriguing way for efficacy testing of new drugs. Therefore, several chamber facilities were installed in recent years with the focus on allergen exposure resulting in currently 15 allergen challenge chamber (ACC) facilities around the globe. 1025

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VIII.H. Allergen challenge testing

Int Forum Allergy Rhinol . Author manuscript; available in PMC 2020 June 10.