PBL 2 Flashcards
what is an autograph?
transplantation of cells, tissues or organs between sites within the same individual
what is an allograft?
transplantation of organs or tissues from a donor to a non-genetically identical individual of the same species
what is a xenograft?
transplantation of organ or tissue between 2 different species
what is histocompatibility?
the property of having the same, or sufficiently similar, alleles of a set of genes called human leukocyte antigens (HLA), or major histocompatibility complex (MHC).
why are immunosuppresents important after an organ transplant?
they prevent organ rejection, they prevent and treat graft-versus-host disease, they minimise destruction of affected tissues
what is graft-versus-host disease?
the donated bone marrow or peripheral blood stem cells view the recipient’s body as foreign, and the donated cells/bone marrow attack the body.
what happens if the organ is not histocompatable with the donor?
MHC molecules act themselves as antigens and can provoke immune response in the recipient, thus causing transplant rejection.
what is the human leukocyte antigen complex?
a group of genes that encode the proteins responsible for identifying foreign agents to the immune system. These proteins are found on the surface of all cells and act as ‘self-markers’ telling the immune system not to trigger a response.Any cell not displaying these specific HLA proteins will be identified as ‘non-self’ by the immune system and will be treated as a foreign invader
what is a graft?
a piece of living tissue that is transplanted surgically
will there always be some degree of rejection in an organ transplant?
yes unless they are twins as the HLA genes will not be identical. this is why you must take immunosuppressants
what is hyper acute rejection?
This occurs within minutes or hours after a transplantation and is caused by the presence of pre-existing antibodies of the recipient, that match the foreign antigens of the donor, triggering an immune response against the transplant.The antibodies react with cells in the blood vessels of the graft, causing blood clots to form, which will prevent blood supply from reaching the graft resulting in immediate rejection of the transplant.
what is acute rejection?
This occurs within the first 6 months after transplantation. Some degree of acute rejection will occur in all transplantations, except between identical twins. Recipients are most at risk in the first 3 months, but rejection can still occur at a later stage. Acute rejection is caused by the formation of antibodies following the detection of non-self antigens in the donated graft.
what is chronic rejection?
Repeated episodes of acute rejection can ultimately lead to chronic rejection of the graft and failure of the transplant. Chronic rejection commonly manifests as scarring of the tissue or organ which can occur months to years after acute rejection has subsided. At present, there is no cure for chronic rejection other than removal of the graft.
what are consequences of long term immunosuppressive therapy following transplant surgery?
increased risks of infection
increased risk of malignancies
bone marrow suppression
cardiovascular risk
what are the 3 types of immunosuppressive drugs?
calcineurin inhibitors
corticosteroids
cytotoxic immunosuppressants
what is the mechanism of calciuneurin inhibitors?
they block the effects of caclineurin which leads to a reduced production of IL-2 and reduced proliferation of T cells
what is the mechanism of action for corticosteroids?
they travel in the blood bound to transcorbin, they enter cells and combine with glucocorticoid receptors in the cytoplasm, this complex enter the nucleus and it suppresses the production of cytokines and can inhibit phospholipase 2 and COX enzymes. overall we get a decrease in T helper cells
what is the mechanism of cytotoxic immunosuppressants?
they prevent cell division and can cause cell cell death . they predominantly act on T cells
platelets release ADP . what does this do?
they activate other platelets and makes them sticky
platelets release thromboxane A2. what does this do? what does serotonin do?
it activates other platelets and acts as a vasoconstrictor
serotonin acts as a vasoconstrictor
what is aggregation?
the gathering of platelets
what is tissue factor? where does it come from?
what does it do?
factor 3 and known as thromboplastin
it leaks into the blood from outside blood vessels and initiates the coagulation pathway
what activates complex 12 in the intrinsic coagulation pathway?
contact with collagen fibres
what catalyses the conversion of prothrombin to thrombin?
prothrombinase and calcium ions
what catalyses the conversion of fibrinogen to fibrin?
calcium ions
what does factor 13 do?
it is a stabilising factor
it strengthens and stabilises the fibrin threads into a sturdy clot
what are the 2 classes of anti thrombotic drugs?
anticoagulants and anti platelet drugs
what are the 4 classes of drugs for anticoagulation therapy?
warfarin, factor X inhibitors, heparin and thrombin inhibitors
what do factor X inhibitors do?
block the activity of clotting factor X which would activate prothrombin to thrombin.
what do thrombin inhibitors do?
bind to and inhibit the activity of thrombin which prevents blood clot formation
what do anticoagulants do?
slow down clotting by reducing fibrin formation, preventing clots from forming and growing
what do anti platelets do?
from clumping and they prevent clots from forming and growing
name 3 types of anticoagulants?
haeprin, warfarin and lepirudin
name 2 antiplatelet drugs?
clopidogrel and aspirin
