- 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