Mast Cell Degranulation: FcεRI Cross-Linking

This simulator renders a mast cell studded with IgE-loaded FcεRI receptors and lets free-floating allergen molecules drift, bind, and bridge them in real 3D. A single binding event does nothing; only when a multivalent allergen physically cross-links two IgE-occupied receptors does the pair light up red, and once enough cross-linked bridges accumulate — tracked live as a cross-link density ρ run through a Hill-function threshold — the cell fires, releasing a visible burst of histamine-carrying granules before resetting to rest. Tune the allergen dose, receptor density, and degranulation threshold to explore why intermediate allergen doses can trigger a stronger reaction than an overwhelming one (the prozone / high-dose hook effect), and fire a pulse to simulate a real sting or exposure event.