Exercise affects systemic basophil responses in humans: Applying an automated and modified basophil activation test (mBAT) in a field study

Basophils are effector cells in type I hypersensitivity reactions. Upon cross-linking of surface-bound (allergen-specific) IgE, basophils release a variety of mediators. Determining the activation of basophils ex vivo with anti-IgE (a basophil activation test or BAT) can be achieved using flow cytometry. However, this requires an experienced laboratory, hampering penetration of the BAT into general allergen diagnostics. Automation of the BAT could make this requirement redundant. Automation of the BAT enables rapid analysis in a field study setting of the effect of prolonged endurance exercise that can prime circulating basophils. A modified near-patient BAT (activation by anti-IgE and fMLF) was developed to identify basophils (SSC^Low and CD193^bright) and their activation status (based on expression of CD63, CD11b and CD62L) using blood samples taken from 7 healthy anonymous volunteers of the hospital's donor service. Due to logistic reasons, the modified BAT (mBAT) was developed at room temperature. Second, blood samples from 18 healthy volunteers were taken during a multiple day walking event to determine the effect of exercise on basophil activation in situ. Eosinophil (SSC^high and CD193^bright) and neutrophil (SSC^high and CD193^dim) activation were also measured as comparators. Anti-IgE- and fMLF-induced activation of basophils in whole blood of both groups showed reproducibility and optimal activation at 1 μg/mL and 0.1 μM, respectively. The field study showed that exercise led to activation of basophils in situ. The fully automated, 24/7 mBAT is feasible for near-patient analysis of priming and/or activation of innate immune cells. This can bring basophil activation testing by mBAT to peripheral care institutes as it does not depend on a specialized laboratory and/or personnel. This study indicates that prolonged exercise leads to activation of basophils in vivo, which might be used to study exercise intolerance in asthmatics.