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16 Cards in this Set
- Front
- Back
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What are the 4 types of transplantation grafts giving a description of each |
Autograft - Transfer of tissue between different sites within the same person (e.g skin graft to another part of the body) Isograft -Transfer between genetically identical members of the same individual (e.g transplant between twins) Allograft - Transfer between genetically non-identical members of the same species (e.g human to human liver transplant) Xenograft - Transfer between species (e.g pigs valve in heart) |
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Out of the 4 different types of graft, which are the most common? |
Allografts (human to human) are the most common type of graft in clinical practice. |
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What is the difference between MAJOR grafts and MINOR grafts? |
Major grafts is when the donor graft antigens are considered to be important in the causation of rejection. Minor grafts contain antigens in the donor which are less likely to cause rejection. |
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What 2 types of molecules pose MAJOR risk to graft rejection? |
HLA - sharing HLA types between donor and recipient is crucial. ABO blood group matching is also essential. (Need to match HLA and ABO!!!) *different organs require differing degrees of closeness in tissue matching and differing degrees of immunosuppressive therapy after surgery* |
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What is the name of the parts of the body which do not require tissue or blood group matching because there is no blood or lymphatic supply to the tissue? |
These tissues into which foreign grafts can be placed are known as PRIVILEGED SITES. *e.g the Cornea is immune privileged* |
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What are the 5 most common complications in transplantation? |
Graft rejection Graft versus host disease (GVHD) Infection - as a result of immunosuppressant therapy) Neoplasia - also as a result of immunosuppression therapy Drug side effects |
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What is the most common cause for graft rejection? |
Most rejection processes are due to incomplete HLA matching between donor and recipient. |
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What are the 4 types of transplant rejection and what type of immune response cells are they mediated by? What is the length of time for rejection to occur in each? |
Hyper-acute = Pre-formed antibody against donor HLA or ABO, Occurs in Minutes Accelerated = Mediated by T cells that are pre-sensitised to donor antigens, Occurs in 2-5 days Acute = Mediated by newly sensitised T cells, Occurs in 7-21 days Chronic = Multifactorial rejection, Occurs in months to years |
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What measures can be taken to prevent the likelihood of a graft rejection? |
ABO blood matching and detection of pre-sensitisation to donor antigens Close tissue matching (Class I & II HLA - especially HLA - A, HLA - B and HLA - DR) Prophylactic Immunosuppressant therapy |
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What type of transplant does Graft vs host disease (GVHD) most commonly occur in? |
GVDH most common in Bone marrow transplants *can occur in other grafts with blood transfusion involved* |
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What circumstances need to occur for Graft versus host disease to develop? |
1. The presence of functioning immunocompetent donor T cells in the graft 2. Defective immunity (Especially T cell function) in the graft recipient 3. HLA differences between donor and recipient |
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What areas of the body are first affected in graft versus host disease? |
GVHD principally causes tissue damage in recipient skin, gut, liver and immune cells. |
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How is GVHD best prevented? |
Careful and very close HLA tissue matching Deplete donor marrow of T cells in vitro prior to grafting |
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What is Xenografting? |
The matching of animal tissue with human tissue |
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What is the problem which occurs in Pig grafts for heart valves? |
All humans have naturally acquired IgM class antibody against pig antigens |
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What is the solution to ensuring a patient excepts a Xenograft (e.g pig valve)? |
To remove the IgM antibody ex-vivo form potential pig organ recipients Breed genetically modified 'silenced' pigs Breed 'humanised' transgenic pigs |
