solid organ transplantation Flashcards
what is autologous transplant
donor and recipient are the same individual (most common)
- e.g. skin graft
what is syngeneic transplant
donor and recipient are genetically identical twins
what is allogenic transplant
donor and recipient are not genetically identical but are from same species
what is xenogenic transplant
donor and recipient are from different species.
what are the types of allogenic donors
Living donors: haematopoietic stem cells- bone marrow transplant Kidney- 1 kidney liver lobe lung lobe- parents donating to a child
Deceased donors: Kidney- both kidneys liver pancreas heart (and lung) cornea and other tissues
What are the compatible donors for blood type A
A,O
What is the antigen on RBC and antibody in plasma for people with blood type A
Antigen on RBC- A
Antibodies against- B
What are the compatible donors for blood type B
B,O
What is the antigen on RBC and antibody in plasma for people with blood type B
Antigen on RBC- B
Antibodies against- A
what are the compatible donors for blood type AB
O,A,B,AB
What is the antigen on RBC and antibody in plasma for people with blood type AB
Antigen on RBC- A,B
Antibodies against- No antibodies against it
what are the compatible donors for blood type O
O
What is the antigen on RBC and antibody in plasma for people with blood type O
No antigen on RBC
Antibodies against- A, B
what is Hyperacute rejection of transplanted organ
occurs immediately after connection of blood vessels.
how can the problem of Hyperacute rejection be overcome
immunoadsorption, plasma exchange, immunosuppression (limited to living donors)
taking away antibodies of the recipients- only appropriate when donor is a living donor so can be planned in advance
what chromosomes are the Major histocompatibility complex (MHC) located on and what genes do they contain
Located on chromosome 6 and contains our HLA genes
what is the structure of HLA class 1 and what exons is the polymorphism located on
3 alpha
1 beta chains
Polymorphism located on exons 2 and 3
what is the structure of HLA class 2 and what exons is the polymorphism located on
2 alpha
2 beta chains
Polymorphism located on exon 2
describe the expression of HLA class 1 (types and what it is present on)
HLA class 1:
A
B
C
Present on all nucleated cells
describe the expression of HLA class 2 (types and what it is present on)
HLA class 2:
DQ
DR
DP
present on APCs (macrophages, dendritic cells and B cells)
Present on activated T cells
what is alloreactivity and how is it overcome
T-cells respond vigorously to non-self HLA molecules .
Major obstacle for transplantation - aim is to match HLA molecules
Describe HLA matching in kidneys, liver and cardiothoracic
Kidneys: aim to match HLA-A, B, DR
Liver: HLA matching not performed
Cardiothoracic: Not feasible due to logistics
Patients can make antibodies against non-self HLA via what routes?
Pregnancy- mother sensitised to HLA type of baby that has been inherited from father- so makes harmless antibodies against them
Blood transfusion- sensitised to HLA type of blood donor
Previous transplant
Describe hyperacute transplant rejection
Patient has pre-formed complement fixing donor reactive antibodies.
Occurs mins/hours after transplant
Extremely rare
Describe acute rejection
Immune mediated: T-cells (cellular) and B-cells (antibodies)
Treat with modulation of immunosuppression
Risk factor for chronic allograft nephropathy
Describe chronic allograft nephropathy
Progressive damage to organs
More slowly compromises organ function than acute rejection
what do HLA class I molecules bind
Binds proteins derived from intracellular proteins, including peptides derived from virus
what do HLA class II molecules bind
Binds peptides dervied from extracellular proteins and cell surface proteins, including peptides derived from bacteria
what are the two tiers of transplant allocation and describe them
Tier A- Patients with match-ability score = 10
Patients with 100% calculated reaction frequency
Patients that have accured 7 years of waiting time
Tier B: all other eligible patients (kidney only)
what does matchability score mean
Matchability score=1 means easy to find HLA matched donor
Matchability score=10 means hard to find HLA matched donor
what does 100% calculated reaction frequency mean
Prescence of HLA antibodies in patient:
0% = none
100% = antibodies present that react with multiple HLA mismatches
