Before revision:  Motivated by recent experimental data demonstrating the capacity of Fas to self-stabilize in their signaling forms , we propose a mathematical model of death ligand-receptor interaction that exhibits hysteresis. This provides an upstream mechanism for bistability in apoptosis, which is seen to be a consequence of biologically observed receptor trimerization.
After revision:  Motivated by recent experimental data demonstrating the capacity of Fas to self-stabilize in their signaling forms , we propose a mathematical model of death ligand-receptor dynamics where FasL acts as a clustering agent for Fas, which form locally stable signaling platforms through proximity-induced receptor interactions. Significantly, the model exhibits hysteresis, providing an upstream mechanism for bistability in apoptosis, which is seen to be a consequence of biologically observed receptor trimerization.