Hyperacute rejection is a Type II (antibody-mediated) hypersensitivity reaction. If the recipient already carries antibodies against the donor's ABO blood-group or HLA class I antigens — from a prior transplant, transfusion or pregnancy, or simple blood-type incompatibility — those antibodies bind donor vascular endothelium within minutes of graft reperfusion:
Site binds when: rand() < k · (titer/100) · (mismatch/100) · dt
Once bound: occlusion(t+dt) = occlusion(t) + (complement/100) · g · dt
Graft occlusion: O(t) = mean( occlusion_i ) over all antigen sites i
Bound antibody activates the classical complement cascade (C1q → C3 → C5b-9, the membrane attack complex), which injures the endothelium and exposes tissue factor and von Willebrand factor. That triggers platelet aggregation and fibrin deposition — a thrombus that grows at each bound site and progressively narrows the vessel lumen.
This 2D view unrolls the vessel wall lengthwise (top panel — antigen sites are placed with a golden-angle spiral, exactly as around the real cylindrical wall, then projected onto the vertical axis), lets you drag or scrub to any position along the graft to see a live lumen cross-section (bottom-left — the red clot mass is the local mean of nearby site occlusions), and plots occlusion and bound-site count over simulated time (bottom-right).
- Antibody titer — how much preformed antibody is circulating; higher titer means more binding events per minute.
- ABO / HLA mismatch — donor–recipient incompatibility severity; at 0% the crossmatch is negative and almost nothing binds, exactly why every real transplant is screened first.
- Complement activity — how fast a bound site converts into an occluding thrombus once antibody has attached.
- Cross-section position — drag the marker on the top panel (or use the slider) to inspect the lumen at any point along the graft.
In practice this reaction is prevented — not treated — by a negative crossmatch and ABO-compatible donor selection before surgery; once thrombosis starts inside the graft it is typically irreversible within minutes to hours.