IgE Cross-Linking Directly Modulates Degranulation and Tslpr Induction upon Food Allergen Challenge

A)   Rationale: Recent data reveals that IgE-cross-linking upregulates thymic stromal lymphopoietin receptor (TSLPR) expression on isolated basophils in a small cohort of allergic asthma patients.  Both IgE and non-IgE signaling pathways facilitate basophil activation, yet it is unclear whether food allergens leads to basophil activation and TSLPR expression solely through IgE:FceRI signaling complexes. We hypothesize IgE-mediated signal transduction pathways are necessary for degranulation, type 2 cytokine IL-4 secretion, and TSLPR induction.

B)   Methods: Heparin-treated whole blood from 12 double-blind placebo-controlled food challenged (DBPCFC) confirmed food allergic patients were treated with IgE-stripping designed ankyrin-repeat protein (DARPin) molecules, E2_79 (monovalent) and bi53_79 (bivalent), and assessed for basophils activation by degranulation markers CD63 and CD203c upon allergen challenge.  The basophils were further assessed for TSLPR induction upon nut allergen challenge.

C)   Results: Treatment with DARPin molecules perturbs IgE binding to high affinity FceRI on primary basophils with minimal disruption of FceRI expression on the plasma membrane. Treatment with DARPins significantly reduced CD63 percentages by >70% and CD203c levels by 58% after IgE cross-linking and food allergen challenge. Furthermore, DARPins abrogate TSLPR induction in primary basophils.

D)   Conclusions: We demonstrated that IgE cross-linking upon food allergen challenge is essential for degranulation as determined by CD63+ and CD203c kinetics.  DARPin treatment further impairs TSLPR induction upon IgE cross-linking and allergen challenge.  Our data delineates IgE-mediated functions in basophils and a novel pathway for TSLPR induction upon food allergen challenge.