Organ Transplant Flashcards
What is an autologous transplant?
A transplant where the donor and recipient are the same individual e.g. skin graft
What is a syngeneic transplant?
A transplant where the donor and recipient are genetically identical twins
What is an allogenic transplant?
A transplant where the donor and recipient are not genetically identical but are from the same species
What is a xenogeneic transplant?
A transplant where the donor and recipient are from different species
What tissues/organs can living donors donate?
Haematopoietic stem cells
kidney
liver lobe
lung lobe
What factors can affect allocation of organs to recipients?
Clinical need waiting time Compatibility Age Age difference Location
How can hyper acute rejection of the transplanted organ due to blood group incompatibility overcome?
Immunoadsorption
Plasma exchange
Immunosuppression
On which chromosomes is the major histocompatibility complex located?
chromosome 6
Which HLA genes come under class I?
HLA-A, HLA-B, HLA-C
Which HLA genes come under class II?
HLA-DR, HLA-DQ, HLA-DP
Which exons are polymorphic on HLA class I molecules?
alpha 1 and alpha 2
HLA class I proteins bind peptides derived from what proteins?
Intracellular proteins including viruses
Which type of T cell do HLA class I proteins bind to?
CD8+ T cell
HLA class II proteins bind peptides derived from what environment?
Extracellular
Which type of T cell do HLA class II proteins bind to?
CD4+ T cell
Which axons are polymorphic on HLA class II molecules?
Alpha 1 and beta 1
Class I HLA molecules are expressed only on APCs and activated T cells whilst Class II HLA molecules are present on all nucleated cells. T/F?
False- the opposite is true
Why is it important that there is diversity within HLA genes within individuals and within populations?
In order to be able to combat as many different pathogens as possible
To increase the chances of species survival after exposure to new pathogens
How is the immune response to a kidney transplant different to the immune response to a bone marrow transplant?
When a kidney is transplanted, the immune system will mount a response against the ‘non-self’ kidney
when bone marrow is transplanted, this replaces the immune system of the recipient and so can generate an immune response against the recipient as the recipient’s tissue and organs are recognised as ‘non-self’ - this is host vs graft disease
It is not practical to HLA match all donor organs to their recipients. How is this overcome?
By immunosuppression of the recipient
Why might the patient already make antibodies against non-self HLA?
Pregnancy
Blood transfusions
Previous transplants
Viral infections
In kidney transplantation, which HLA genes are matched?
HLA-A, HLA-B, HLA-DR
HLA matching is used for liver and heart transplants. T/F?
False
The presence of preformed donor specific HLA antibodies is a contra-indication to transplantation. T/F?
True
Acute rejection of the transplanted organ is mediated by which cells?
T and B cells
How does hyper acute rejection of a transplant result in irreversible ischaemic damage?
By preventing vascularisation of the graft
What factors can cause acute rejection of a transplant?
Poor HLA matching / presence of HLA autoantibodies
Sub-optimal immunosuppression or non-compliance of the patient
What factors can cause delayed graft function?
Older donor / poor graft quality
Cause of death injury
Preservation injury
Ischaemic Injury
What factors, other than delayed graft function and acute rejection incidents, can lead to chronic allograft nephropathy?
Hypertension
Hyperlipidemia
Toxic effects of immunosuppressants cyclosporin and tacrolimus
Describe the 5 step priority scale of the allocation criteria from deceased heartbeating donors through the UK scheme?
- paeds patient (hla match), highly sensitised
- paeds patient (hla match)
- adult patients (Hla match) highly sensitised
- adult patients (acceptable mismatch)
- all other eligible patients
How often do patients on the transplant list have a HLA alloantibody test?
Every 3 months
