Makindo Medical Notes

📖 Overview

Transplant rejection is the immune system’s response against donor tissue. It is classified by timing, mechanism, and pathology into hyperacute, acute, and chronic forms. Understanding these helps guide prevention, diagnosis, and management.

🩸 Hyperacute Rejection

• Timing: Occurs within minutes to hours after transplantation.
• Mechanism: Pre-formed recipient antibodies against donor ABO or HLA antigens activate complement, causing thrombosis and graft necrosis.
• Clinical: Immediate graft failure, often noticed on the operating table (organ turns cyanotic, fails to perfuse).
• Histology: Neutrophilic infiltration, fibrinoid necrosis, thrombosed vessels.
• Management: Irreversible → graft must be removed.
• Prevention: Careful ABO and HLA cross-matching before transplant.

⚡ Acute Rejection

• Timing: Days to 3 months after transplant, but can occur later if immunosuppression is inadequate.
• Mechanism: T-cell mediated (cellular) and/or antibody-mediated (humoral).
• Clinical: Fever, graft tenderness, falling urine output, rising creatinine (in renal transplants).
• Histology: Interstitial lymphocytes, tubulitis, intimal arteritis.
• Diagnosis: Biopsy of transplanted organ is essential (e.g. kidney in iliac fossa).
• Management: High-dose corticosteroids, T-cell depleting therapy (e.g. anti-thymocyte globulin), optimize baseline immunosuppression.

⏳ Chronic Rejection

• Timing: Develops over months to years.
• Mechanism: Ongoing mixed cellular and humoral responses lead to chronic inflammation, vascular changes, and fibrosis.
• Clinical: Gradual, irreversible decline in graft function, proteinuria, hypertension.
• Histology: Vascular intimal thickening, interstitial fibrosis, tubular atrophy.
• Differential: Calcineurin inhibitor toxicity (biopsy distinguishes).
• Management: Irreversible; supportive care and consideration of re-transplantation.

📌 High-Yield Exam Summary

• 🩸 Hyperacute: Immediate, antibody-mediated, irreversible, prevented by cross-matching.
• ⚡ Acute: Days–months, T-cell mediated, diagnosed on biopsy, treatable with immunosuppression.
• ⏳ Chronic: Months–years, mixed immune mechanisms, causes fibrosis, irreversible.