The 3D companion sim renders one site with a single well-mixed cytokine/immune-cell pair obeying a local positive-feedback loop. This 2D version keeps that exact local law but runs it independently at six organs, then couples them through a shared, well-mixed blood compartment via a first-order perfusion exchange — the actual route a real cytokine storm uses to become systemic instead of local:
dC_i/dt = production·I_i − clearance·C_i − k_perf·(C_i − C_blood)
dI_i/dt = recruitment·C_i·(1−brake) − death·I_i
dC_blood/dt = mean_i[ k_perf·(C_i − C_blood) ] − blood_clearance·C_blood
Only the origin organ starts with an elevated trigger; every other organ begins near baseline. Whether the storm ever reaches them depends entirely on vascular coupling k_perf — a parameter the single-site 3D model has no room to express, since it has only one compartment. At low coupling the origin organ can burn out or stabilize in isolation; at high coupling, blood cytokine rises fast enough to seed a positive-feedback loop at distant organs before the origin resolves — the network mechanism behind real multi-organ dysfunction syndrome.
- Origin organ and trigger strength set where and how large the initial burst is (same three presets as the 3D scene).
- Negative feedback is the same IL-10-style brake as the 3D model, applied identically at every organ.
- Vascular coupling is the 2D-native addition: it is the perfusion rate that lets cytokine (not immune cells — those stay resident) cross from one organ's local loop into the shared blood pool and back out into every other organ.
- Time to 2nd organ is a number the single-compartment 3D model cannot produce at all — it only exists once more than one site is simulated.