- Occurs within minutes (to hours) – so quick that the surgeon is sometimes able to visualise characteristic changes whilst sill performing the anastomosis of blood vessels.
- There is rapid agglutination (clumping together of blood cells), which is particularly risky for renal transplant patients. The reaction seen is the same as a blood transfusion reaction.
- Due to preformed antibodies already present in the recipient at the time of transplant
- Most commonly due to mismatched blood group – so risk can be minimised if blood groups are matched.
- There is no treatment
- The transplanted organ must be removed immediately to prevent a dangerous systemic inflammatory response
- Can occur from 1 week – 3 months after transplantation
- Rarely it can occur months or years later
- It can be successfully treated
- If recurrent, it can become a chronic rejection.
In some senses, a varying degree of acute rejection occurs in all transplants. It is due to HLA incompatability – a degree of which exists between all individuals (except identical twins). there is a T-cell mediated reaction against the transplanted tissues, which results in endovascular damage, as well as lysis and necrosis of the transplanted tissue. The kidneys and liver are at particular risk.
Accelerated acute rejection – the T cells are re-activated
- Reaction occurs within days
Acute rejection – the T cells are sensitised and subsequently activated
- Reactions occurs within days-weeks
- Usually require tissue biopsy, which reveals:
- T-cell infiltration of the transplanted tissue
- Structural damage of the transplanted tissue
- Vascular damage of the transplanted tissue
- Can be managed with immunosuppressant agents e.g:
- Anti-monoclonal antibodies (e.g. infliximab, Rituximab)
- Plasma exchange (plasmapheresis) is also an option
- Some centres will use induction regime of plasma exchange or monoclonal antibodies to reduce the chance of acute rejection in high risk patients
This a controversial topic. It is thought chronic rejection is an antibody mediated process that occurs after months or years, and results in vascular damage.
- Lung transplant
- Has the worse outcomes (mean survival about 5 years), as a result of chronic rejection
- The rejection results in bronchiolitis obliterans, and is characterised by progressive airways obstruction, causing SOB and dry cough
- Chronic rejection is a progressive, irreversible process
- The only curative treatment is re-transplant