IgE Occupancy and Antigen Valency Cooperate to Control FcεRI Aggregation Geometry and Signaling Efficiency

Area of Science:

• Immunology
• Allergy research
• Molecular biology

Background:

• Crosslinking of IgE-bound FcεRI receptors by allergens triggers Type 1 allergy signaling.
• The influence of allergen characteristics and IgE occupancy on FcεRI aggregation and signaling is not fully understood.

Purpose of the Study:

• To investigate how allergen valency and epitope arrangement affect FcεRI receptor aggregation and downstream signaling.
• To probe antigen-dependent signaling using defined multivalent antigens.

Main Methods:

• Utilized Phl p 1-specific IgE and recombinant fusion proteins with varying valencies (MB1N, MB1N1C, MB2N, MB4N).
• Employed Monte Carlo simulations, electron microscopy, and single-particle tracking to analyze receptor aggregation and mobility.
• Measured mast cell degranulation and intracellular calcium (Ca2+) responses.

Main Results:

• Tetravalent MB4N induced significantly stronger degranulation and Ca2+ responses compared to bivalent antigens (MB1N1C, MB2N).
• MB4N mediated signaling even at low IgE occupancy and in Lyn-deficient cells.
• MB4N formed larger, complex FcεRI aggregates with slower mobility, unlike the linear chains formed by bivalent antigens.

Conclusions:

• Allergen valency and the spatial arrangement of epitopes are critical determinants of FcεRI aggregate organization.
• FcεRI aggregate structure directly influences effector cell activation in Type 1 allergy.
• Understanding these mechanisms can inform strategies for managing allergic diseases.