Transplantation: Allo-Tolerance Induction vs Indefinite Immunosuppression

A graft is a standing allo-antigen load on the same switch. A deep transient induction crosses the negative saddle-node and yields durable operational tolerance off-therapy, while continuous sub-critical immunosuppression only contains rejection and the graft is rejected on withdrawal. The induction threshold rises the longer the alloresponse consolidates. DIRECTION/CLASS only, not medical advice. Grade [V].

A graft presents a standing allo-antigen load — the same substrate problem with a larger residual drive, whose induction threshold is the negative saddle-node shifted by the load. A deep transient induction yields durable operational tolerance off-therapy, while continuous sub-critical immunosuppression only contains rejection and rejects on withdrawal; the induction threshold rises the longer the alloresponse runs unopposed, defining an induction window. Host-versus-graft and graft-versus-host are the same crossing with the compartments swapped; measured dynamics [V], absolute scale [O].

Transplantation: induction vs indefinite immunosuppression

A graft presents a standing allo-antigen LOAD — the same substrate problem with a larger residual drive. The induction threshold is again the negative saddle-node, shifted by the load: the critical suppression depth at which operational tolerance is induced makes the total drive reach −1×spinodal, i.e. suppress_crit = 1 + allo-load (measured 1.504× the spinodal). A deep transient induction yields DURABLE operational tolerance — the alloreactive trajectory empties to 0.00 of capacity and the graft is accepted off-therapy — whereas continuous sub-critical immunosuppression only CONTAINS rejection while applied and REJECTS on withdrawal (trajectory 1.00, the basin refilled). The transplant-specific fact is timing: the alloresponse CONSOLIDATES the longer it runs unopposed, so the measured induction threshold RISES with the delay-to-induction (suppress_crit 1.504 early → 1.918 late) — an induction window in which tolerance is easier before the alloresponse consolidates. The mechanism is direction-symmetric: host-versus-graft and graft-versus-host are the same saddle-node crossing with the alloreactive compartment and target swapped.

Part of the disease/treatment axis: a pathological immune state is a latched basin, and the durable class of intervention moves the system across the saddle-node rather than only holding the drive down, which relapses on withdrawal.