- Clinical science
Transplantation is the process of transferring an organ or a part thereof (known as a graft) from one donor to him/herself (autologous transplantation) or to another recipient (allogenous transplantation if the individuals are not identical twins). In addition to being subject to strict legal requirements, the donor and recipient must be histocompatible in allogenous transplantations in order to minimize the risk of transplant rejection. Because the major histocompatibility complex (MHC) is only perfectly matched in isotransplantation (involving the transfer of genetically identical tissue, e.g., from an identical twin), allogenous transplantation subsequently requires immunosuppressive therapy.
Major histocompatibility complex (MHC) and (HLA)
- MHC: a gene cluster on chromosome 6 that codes for HLA molecules
- HLA: proteins present on the surface of all cells that display antigenic peptides as a normal physiological function so that they can be recognized by T lymphocytes as either self or non-self antigens
- Types of MHC
- See for more details.
- Definition: recognition of a foreign antigen as a non-self antigen by a host
- Clinical importance: Activation of a particular T cell by a foreign HLA peptide results in clonal proliferation of that type of T lymphocyte, a process that is mediated by IL-2 and leads to acute rejection.
Prerequisites for organ matching
Recipient serum is examined for preformed antibodies (so-called donor-specific antibodies) against donor T and B lymphocytes.
- A positive cross-match against donor T and B lymphocytes indicates a high risk of hyperacute rejection; therefore, the transplantation must not be performed.
- A negative cross-match against T cells but a positive cross-match against B cells indicates a higher risk of acute rejection, but transplantation may still be performed with a high level of caution.
- A negative cross-match against T and B cells indicates a lower risk of rejection reactions; therefore, transplantation may be performed.
- Recipient serum is examined for preformed antibodies (so-called donor-specific antibodies) against donor T and B lymphocytes.
- ABO compatibility
|Types of graft based on histocompatibility between donor and recipient|
|Xenograft|| || |
autograft transplantation. is not required for
- The organ is harvested from brain-dead donor (BDD) or donor after cardiac death (DCD) .
- Contraindications for organ donation
- The following conditions are NOT contraindications to organ donation:
- The organ is surgically harvested from a living donor (usually a relative) at the time of the transplant surgery.
- Only kidney transplantation and liver transplantation can be performed using grafts from living donors.
- Disadvantages: increased morbidity and mortality in the donor
- Induction therapy using anti-T-lymphocyte antibodies
- Maintenance therapy: commonly via a triple-drug regimen
immunosuppression, and the risk of infection increases. Too little, and the risk of rejection increases! is a balancing act: Too much
- Technique: heterotopic implantation in the iliac fossa connecting donor ureter to recipient bladder
- Serial monitoring of renal function tests
- Diagnostic algorithm in the case of renal dysfunction following renal transplantation
- Consider pre-renal causes of acute renal failure.
- Measure urine protein and perform a dipstick urine test for hematuria.
- Hematuria or proteinuria are present: Perform a renal biopsy directly.
Hematuria and proteinuria are not present:
- If the patient is not on anticalcineurins → perform a renal biopsy
- If the patient is on anticalcineurins → measure serum anticalcineurin levels
- ↑ Anticalcineurin levels: reduce anticalcineurin levels and remeasure creatinine
↔︎ Anticalcineurin levels (i.e., within the target range): perform renal and bladder ultrasound to rule out obstruction
- If evidence of obstruction is present: perform renal scintigraphy
- ↓ Anticalcineurin levels: perform a renal biopsy
- Prognosis: graft functions for approx. 14 years, longer if received from a living donor
- Vascular complications
- Biliary leak
- Biliary stricture
Diagnostic algorithm in the case of clinical or laboratory features of hepatic dysfunction
< 6 months post-transplant; : duplex ultrasonography to identify biliary or vascular pathology
- If there is no evidence of biliary dilation or vascular pathology: liver biopsy
- If evidence of biliary dilation is present: ERCP or percutaneous transhepatic cholangiography
- > 6 months post-transplant: liver biopsy
- < 6 months post-transplant; : duplex ultrasonography to identify biliary or vascular pathology
- Post-transplant care
- Pulmonary hypertension → right heart failure
- Surveillance endomyocardial biopsies to identify rejection reactions
Types of HSCT
|Autologous stem cell transplantation||Allogenous stem cell transplantation|
|Disadvantages|| || |
- Graft failure
- Definition: graft failure as a result of damage to the graft by the host's immune response
|Types of graft rejection|
|Hyperacute rejection||Acute rejection||Chronic rejection|
|Frequency|| || || |
|Onset|| || || |
|Clinical findings|| || |
|Diagnosis|| || |
|Prevention|| || || |
|Treatment|| || || |
Graft rejection manifests as a failure of the transplanted organ and is very difficult to distinguish from other post-transplant complications. A biopsy is required to confirm the diagnosis.
- Definition: damage to the host as a result of a systemic inflammatory reaction induced by T lymphocytes present in the graft
- Types of GvHD
|Acute GvHD||Chronic GvHD|
|Onset|| || |
|Clinical presentation|| |
(< 1 month after transplantation)
|Late onset||1–6 months|
|> 12 months|
- Screen both the donor and the recipient for infections and treat any existing infections in the recipient.
- Ensure that vaccinations are up-to-date.
- Monitoring for the following infections:
- Universal prophylaxis
- Incidence: 0.4% following organ transplantation
- Common malignancies
We list the most important complications. The selection is not exhaustive.