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

Abstract

The basophil activation test (BAT) is an ex vivo functional assay that measures by flow cytometry the degree of basophil degranulation after stimulation with an allergen. In recent years, there has been an increased interest in the diagnostic value of the BAT as it has the potential to mimic the clinical phenotype of sIgE sensitized patients, in contrast to allergen-specific IgE levels. This diagnostic potential would be of particular interest for food allergies present early in life such as peanut, cow's milk and eggs, which require an expensive, time-consuming and patient unfriendly oral food challenge (OFC) for diagnosis. However, routine applications of the BAT for clinical use are not yet feasible due to the lack of standardized protocols and large clinical validation studies. This review will summarize the current data regarding the application of the BAT in food allergy (FA) for cow's milk, egg and peanut, being the most common causes of FA in children. Additionally, it will discuss the hurdles for widespread clinical use of the BAT and possible future directions for this diagnostic procedure.

Keywords: basophil activation test; chicken egg; cow’s milk; diagnosis; food allergy; peanut.

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.

Figure 2

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