Synthetic Allergen Design Reveals the Significance of Moderate Affinity Epitopes in Mast Cell Degranulation

This study describes the design of a well-defined homotetravalent synthetic allergen (HTA) system to investigate the effect of hapten–IgE interactions on mast cell degranulation. A library of DNP variants with varying affinities for IgE^DNP was generated (K_d from 8.1 nM to 9.2 μM), and 8 HTAs spanning this range were synthesized via conjugation of each DNP variant to the tetravalent scaffold. HTAs with hapten K_d < 235 nM stimulated degranulation following a bell-shaped dose response curve with maximum response occurring near the hapten K_d. HTAs with hapten K_d ≥ 235 nM failed to stimulate degranulation. To mimic physiological conditions, the percent of allergen specific IgE on cell surface was varied, and maximum degranulation occurred at 25% IgE^DNP. These results demonstrated that moderate hapten–IgE affinities are sufficient to trigger mast cell degranulation. Moreover, this study established the HTA design as a well-defined, controllable, and physiologically relevant experimental system to elucidate the mast cell degranulation mechanism.