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Reference: Transplant Rejection
| Type & Onset |
Pathogenesis & Histology |
Hyperacute
Minutes to hours |
Pre-existing recipient antibodies react to donor antigen (Type II hypersensitivity). Activates complement.
Widespread thrombosis of graft vessels causing ischemia and necrosis. Graft must be removed. |
Acute (Cellular)
Weeks to months |
CD8-positive and CD4-positive T lymphocytes activated against donor Major Histocompatibility Complexes (Type IV hypersensitivity).
Dense mononuclear interstitial infiltrate and tubulitis. |
Acute (Humoral)
Weeks to months |
Antibodies develop after transplant against donor Human Leukocyte Antigens (Type II hypersensitivity).
Necrotizing vasculitis with neutrophilic infiltrate; complement component 4d deposition in peritubular capillaries. |
Chronic
Months to years |
CD4-positive T lymphocytes respond to recipient antigen-presenting cells presenting donor peptides. Cytokine release stimulates smooth muscle proliferation.
Vascular wall thickening (arteriosclerosis), luminal narrowing, interstitial fibrosis, parenchymal atrophy. |
Mnemonics & Tips
The "TIMe" scale:
- Thrombosis = Hyperacute (Minutes/Hours, Pre-formed antibodies).
- Infiltrates = Acute (Weeks/Months, Lymphocytes or vasculitis).
- Massive Fibrosis = Chronic (Months/Years, Vascular thickening).
Click the diagram below to zoom into the histological patterns:
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