The Basophil Activation Test for Clinical Management of Food Allergies: Recent Advances and Future Directions

Figures & data

Figure 1 Basophil activation test principle. At a resting mode, the activation marker CD203c is expressed at low levels, but upon activation it is rapidly up-regulated. In addition, when the basophil is in a resting mode the activation marker CD63 is mainly present inside the cell granules. Upon activation, after exposure to an allergen, the granules fuse with the cell membrane and CD63 is exposed on the cell surface and can be detected by labelled antibodies with subsequent flow cytometry. Therefore the expression of CD63 is closely associated with degranulation.

Table 1 Technical Considerations for Widespread Use of the BAT

Validation and Standardization
Current Challenge	How to use the proper test to validate and standardize a new tool such as the BAT
Proposal	DBPCFC best current option - Gold standard for FA diagnosis - Removes patient and observer bias
Pitfalls	DBPCFC has limitations - 3% false positives, 3% false negatives and 10% dubious outcomes
Allergen Preparation
Current Challenge	Factors impact the basophil surface activation markers dose-response curve: affinity of the antigen for the cell-bound IgE antibodies, density of the epitope-specific IgE antibodies and epitope spreading of the IgE antibody
Proposal	Include a broad range of allergen concentrations to better evaluate the effect of the allergen in the basophil response
Pitfalls	Most FA diagnostic tools include mainly water-soluble allergens, thus lipophilic allergens are missing Which processed allergens should be used in the BAT still require research
Basophil Identification/Activation Markers
Current Challenge	For a valid interpretation of the results, the precise identification of the basophil population is crucial Since several markers can be measured, the BAT is a valuable tool as it can assess various immunological pathways providing valuable insights into immune mechanisms of allergic disease
Proposal	Studies that compare different identification and activation markers in the same population of patients are needed
Pitfalls	Researchers need to be aware that the current data suggests that depending on the allergen and the cohort used, there might be variability in the sensitivity and specificity of the basophil activation markers.
Read-out Parameters
Current Challenge	Establish the most effective way to measure basophil activity. At the moment, it is advised to measure to first measure basophil reactivity and then measure basophil sensitivity.
Proposal	The area under the dose-response curve (AUC), a marker of both reactivity and sensitivity is gaining attention since it measures at multiple allergen concentrations lowering the risk of false outcomes
Pitfalls	“Basophil anergy”, a non-responding basophil to IgE receptor-mediated signalling after stimulation with one or more types of allergen remains a problem in approximately 10% of cases.

Figure 2 Summary of the key messages of the current status of applying BAT in allergy diagnostics and immunotherapy.