Transplant Immunology Flashcards
(46 cards)
Transfer of one’s own tissue from one site to another.
Autograft
Transfer of tissue between identical twins.
Isograft
Transfer of tissue between genetically different species.
Xenograft
Transplant into an anatomical normal recipient site.
Orthotopic transplant
Transplant into anatomically abnormal site.
Heterotopic transplant
Are transplants ever rejection-free?
No - always have some degree of rejection.
What is rejection?
An immune-mediated response; immune cells are attacking a foreign body. This is particularly problematic for organs and tissues that are highly vascularized.
What causes rejection?
Recognition of foreign MHC antigens by T cell activation.
What does not express MHC? How is matching done for this?
RBC - recipients must be matched for ABO and Rh blood types.
Explain the mouse experiment.
Mouse B got some Mouse A bits transplanted onto it. Acute rejection occurred 10-14 days out. Another Mouse B got some Mouse A bits transplanted onto it, as well as first Mouse B’s bits. Acute rejection occurred 3-7 days out. 3rd Mouse B got Mouse A bits and an injection of 2nd Mouse B’s lymphocytes. Hyperacute rejection occurred 3-7 days out - added leukocytes to presensitized donor tissue and response is quicker.
Do we have antibodies for our own antigens?
No
What do we make antibodies to in terms of blood?
The antigen we lack in the ABO blood group system
Explain the antibodies and antigens of blood.
2 antigens (agglutinogens A & B) on surface of RBC that allow immune system to recognize cell as self. 2 antibodies (agglutins - anti-A & anti-B) in the plasma. H antigen is foundation upon which A & B antigens are built. A gene codes for a transferase that adds N-acetylgalactosamine to terminal sugar of H-antigen. B gene codes for enzyme that adds D-galactose to terminal sugar of H antigen.
What is Rh factor?
Rhesus factor - protein that 85% of the population contains in their blood (RhD+).
ABO blood typing that determines antigens on patient’s or donor’s blood. Cells are tested with the antisera reagents anti-A, anti-B.
Forward typing
ABO blood typing that determines antibodies in patient’s or donor’s serum of plasma. Serum is tested with reagent A1 and B cells.
Reverse typing.
Why is it a problem for an Rh(-) mother to be pregnant with an Rh(+) baby?
Blood mixing happens during birthing. The mother’s blood will be exposed to fetal blood, causing a Type II hypersensitivity response. Antibody binding to antigen activates the classical complement pathway, leading to MAC, which causes blood lysis and hemolysis in the mother’s next pregnancy, as during this one she will have antibodies against her baby’s Rh(+) blood.
Matching MHC Class I (especially HLA-_) and Class II HLA-__ alleles is more important for ________ _______ than matching other MHC antigens.
….B…..DR…..successful transplantation….
Transplants must always be matched for what type of antigens?
Blood type
What types of molecules are MHC Class I?
Almost all nucleated cells
What types of molecules are MHC Class II?
APCs, B-cells
What is the name of the following phenomenon involving MHC: multiple variants of each gene within the population as a whole?
Polymorphism
What are the 2 mechanisms of allogenic transplant rejection?
Direct presentation/alloreactivity
Indirect presentation/alloreactivity
This mechanism of allogenic transplant rejection involves replication of an intact MHC molecule displayed by donor APC in the graft. Self MHC molecules recognize the structure of an intact allogenic MHC molecule. It is most common in acute rejection and involves both CD8 & CD4 T cells.
Direct presentation/alloreactivity
