Unit 2 - Transplants Flashcards
What is transplantation?
Process of moving cells, tissues or organs from one site to another for the purpose of replacing or repairing damaged or diseased organs and tissues
How are transplant donor and recipient matched?
Blood group
Tissue typing
Recipient’s blood serum reaction to donor cells
Why are transplant donor and recipients matched?
To minimise the risk of rejection
What causes transplant rejection?
The immune systems identifies the transplant as foreign, triggering a response that will ultimately destroy the transplanted organ or tissue
What type of drugs are given to prevent and to treat transplant rejection by dampening the overall immune response?
Immunosuppressive drugs
What are the problems with using immunosuppressive drugs?
Patients are more susceptible to disease as well as being associated with numerous unwanted side effects
Which tissues and organs can be transplanted?
Heart Kidneys Thymus Liver Lungs Pancreas Intestine
What are the four types of transplant?
- autografts/autologous grafts
- syngeneic/isografts
- allogeneic grafts
- xenogeneic grafts
What is an autograft transplant?
Transplant between sites within the same individual
- skin grafting
- bone marrow
What is an isograft transplant?
Transplant between two genetically identical individuals
- monozygotic twins
What is an allogeneic graft?
Transplant between two genetically different individuals of the same species
- heart
- lung
- kidney
- liver graft
What is an xenogeneic graft?
Transplant between individuals of different species?
What is a stem cell transplant?
Stem cells are cells that have the capacity to develop into a range of different types of cells in the body
- blood stem cells (haematopoietic stem cells) can develop into all the different cells found in the blood and are donated to replace damaged or destroyed blood cells
What are haematopoietic stem cells used to treat?
Certain types of cancer
- leukaemia
Blood diseases where the bone marrow has become damaged, preventing the production of healthy blood cells
How are haematopoietic stem cells harvested?
- directly from the bone marrow
- from umbilical cord blood from consenting mothers following childbirth
What are the two major alloantigens?
ABO antigens
- routine to cross match donor with recipient blood serum
MHC proteins that are co-dominantly expressed on the surface of our cells
- donor MHC being recognised by the recipients immune system as foreign
What encodes for MHC?
Human Leukocyte Antigen (HLA)
Which cells are MHC class I found on the surface of?
All nucleated cells
- act as ‘self-markers’ telling the immune system not to trigger a response
What is histocompatibility?
Degree of similarity between the HLA genes of the donor and recipient
What are the two types of compatibility test that are carried out for transplants?
- tissue typing
- cross matching
How is tissue typing carried out?
- a blood sample is taken from the recipient to identify the HLA antigens present on the surface of their cells to help find a histone compatible donor
- the more alike the HLA types of the donor and recipient are, the more likely a transplant will be successful
- family members, in particular siblings, are often the best HLA matches due to their genetic similarity
How is cross matching carried out?
- blood samples are taken from both the recipient and donor and the cells of the donor are mixed with the blood serum of the recipient
- if the recipient’s antibodies attack the donor cells, they are considered a positive match and transplantation will not be suitable due to increased risk of hyper-acute rejection
What are the 6 HLA antigens that are studied for tissue typing?
Two each at
- HLA-A
- HLA-B
- HLA-DR
What is alloreactivity?
MHC molecules invoke powerful immune response from allogenic T-cells
