Transplant Flashcards
Allograft
Unrelated
Syngraft
Monozygous twin
Xenograft
Different species
Autograft
Same person
Are syngrafts rejected
No
Allograft rejected
Yup
Xenograft
Hyperactive rejection
Xenograft
Foreign
Hyperactute rejection
Preformed antibodies to HLA class I antigens or antigens of the ABO blood group.
What causes acute or accelerated acute rejections
Cellular allorecognition of the graft
GVHD
Transfer of immunocompetent allogenic cells into an immune depressed individual leads to these rejecting the recipient
Good hla matching
Prolongs graft survival
Done for renal
Why is hla matching not done for liver, heart and lungs
Short periods for which the latter organs maintain their function when explanted
Presensitization
Presence of preformed antibodies to HLA class I or ABO antigens in the recipients blood, it tested for in renal but not others
When rejected organs are biopsies, what do they contain?
Inflammatory infiltrate with mononuclear white blood cells(lymphocytes and macrophages, CD4, 8, macrophages, B cells and NK cells)
When a virgin helper CD4 cell sees an alloantigen, presented by APC what two options can it become if there is costimulation
TH1 or TH2
If the surrounding medium is rich in IL12, a macrophage derived cytokine, what will the virgin THCD4 become with antigen presentation
TH1
What does TH1 do
Activate CD8 and macrophages through IL2 and IFNy
If the surrounding is rich in IL-4 the virgin CD4 T cell will become what
TH2
What does TH2 do
Secrete IL4 and IL10 and direct B cells and antibody production
What CD4 predominates in rejection
TH1
What does IFNy from TH1 do
Recruit and activate macrophages and enhance MHC expression on the graft, making it particularly susceptible to the cytotoxic action of CD8 cell
What does IL2 do
Fav our the activation of cytotoxic T cells
Alloantigen
Antigen recognized during rejection
What are the key allantigens
MHC-HLA molecules
Direct allorecognition
Recipients immune system can recognize an intact MHC
Indirect allorecognition
Peptide derived rom the foreign MHC could be presented on APC
Is direct or indirect allorecognition more common
Direct
Hyperacute rejection
Minutes
Preformed antibodies
Accelerated rejection
1-5 days
T cells
Acute rejection
From 2 week
T cells
Chronic rejection
Months to years
Antibodies, complement, adhesion molecules
Hyperacute rejection is mediated by ___ __ in the recipient that are directed against antigens of the donor organ
Preformed antibodies
Example of hyperacute rejection
ABO blood group barrier Antibodies against HLA class I from previous transfusions, transplants or pregnancies
Where are ABO blood group antigens presented
Endothelial cells
How manage hyperacute rejection
Preventative
Accommodation
Accommodation
Temporary depletion of natural antibodies may result in long term graft survival, despite the return of antibodies in the presence of their specific target antigens
Acute rejection is mediated by ____ and becomes apparent _ days post op
T cells
7
In acute rejection, how do T cells see alloantigen
Mainly direct
What cells infiltrate in acute rejection
Lymphocyte and monocyte
Accelerated acute rejection
1-5 days
T cells that have been sensitized to alloantigen (pregnancy, transduction)
How treat acute rejection
Suppression
Chronic rejections appears _ or _ after successful transplantation
Moonthe years
Is cell infiltration a major feature of chronic rejection
No
in chronic rejection __ release IL1, 6 TNFa
Macrophages
How it is expected that chronic rejection occurs
Early damage to the vascular endothelium is predisposing
Endothelium further damaged by antibodies to alloantigen, deposition of immune complexes, activation of complement , exposure of collagen and activation of the clotting cascade
FAVORING ENDOTHELIAL CELL PROLIFERATION and narrowing of the vascular lumen
GVH
Grafts have immunocompetent cells recognize alloantigen of the recipient
GVH is common after transplantation of __ ___
Bone marrow
What happens when GVH becomes symptomatic
It is GVHD
GVHD divided into two entities
Acute disease (1-2 months) Chronic disease(develops 2-3 months)
What does GVHD effect in humans
Skin, liver, intestinal tract, immune system
How long does GVHD happen after bone transplant
Days weeks
Characterization of GVH
Erythema on palms and soles and ears
Hyperbilirubinaemia
Diarrhea
Characterization of severe GVHD
Jaundice, increased Alkaline phosphatase, which denotes cholestasis, and of transaminases, a ding of liver damage
Diarrhea abdominal pain
What causes the symptoms of GVHD
Epithelial cell injury
Chronic GVHD shares certain clinical characteristics with __ __
Systemic sclerosis
Prophylaxis for acute GVHD
Combination of methotrexate and ciclosporin
Treatment of established GVHD
Methylprednisolone, ciclosporin/tacrolimus
Anti-CD52 monoclonal antibody campath1
Tissue typing
Kidneys bc robust-can bee 48 hours cold
HLA types kidneys have a graft survival in 1st year os ___% while nonmatched have __%
88 79
How test for presenstization
Incubating the serum of the recipient and the lymphocytes of the donor. Binding of antibodies in the recipient serum is analyzed by flow cytometry
Presensitization is an absolute ___ in renal transplant
Contradiction
Is presensitization evaluated in cardiac and liver transplantation
No
Immunosuppressive drugs
Dampening down the immune system
Azathioprine
Inhibits purine synthesis
Corticosteroids
Block cytokine gene expression
Ciclosporin A; tacrolimus
Block Ca2+ dependent T cell activation pathway
Sirolimus
Blocks il2 triggered proliferation and CD28/CTLA4 mediated co stimulators signals
Azathioprine
Purine antagonist and functions as an effective antiproliferative agent.
Corticosteroids have multiple effects on the immune system
Decrease B cells and inhibit monocyte trafficking , T cell proliferation and cytokine gene expression
Side effects of corticosteroids
Skin, bones, and other tissues continue to present problems in clinical
Glucorticoid:prednisone
Given immediately before or at the time of transplantation
Methylprednisone
Administered immediately upon diagnosis of beginning rejection and continued once daily for 3 days
Do prednisone and azathioprine act non specifically on the immune system
Yup
Ciclosporin a
Calcineurin inhibitor
Small fungal cyclic peptide
Reduce GVHD following bone marrow transplant
Major effects of ciclosporin a
T cells-inhibit il2 secretion
Stimulate production of cell growth inhibitory cytokines, such as TGFb
What does TGFb do
Inhibits both T cell proliferationa nd the generation of cytotoxic lymphocytes , a heightened production of tgfb may contribute to the immune suppressive activity of ciclosporin A
Ciclosporin a side effect
Nephrotoxicity
Tacrolimus
Macro life antibiotic isolated from a Japanese soil fungus, streptomyces T
Similar effects and side effects of ciclosporin
Side effects tacrolimus
Renal
Ciclosporin and tacrolimus are what
Calcineurin inhibitors
Sirolimus
Rapamycin , macrocyclic lactose that inhibits biochemical pathways that are required for cell progression through the late G1 phase or entry into the S phase of the cell cycle and is labeled as an antiproliferatice
Side effects sirolimus
Hypertriglyceridaemia
Antibodies can be used to target specific immune cells thought to be involved in rejection
Target cells are abolished or lessened through antibody directed cell lysis or modulation of surface molecules
Monoclonal antibody
Monospecificity and can be purified to homogeneity
Since the 80s, ALG and ATG have been used by many transplant centers for the treatment of rejection episodes (antilymphocyte globulin and antimyocyte globulin)
These polyclonal antisera are composed of multiple antibodies specific for a variety of lymphocyte cell surface molecules
Monoclonal anti CD3
OKT3 monoclonal antibody sees human cd3
Treat recipients of allograft in clinical transplantation
Intravenous administration of OKT3 clears T cell from circulation by opsonization
Disadvantage of anticd3 molecule
Side effects and development of anti mouse antibodies in 75% of ppl
Monoclonal anti-cd4 and anti-cd8
Okt4
In clinical trials
Monoclonal antibodies specific for activation antigens
When T cells respond to antigen and become activated, they express IL2 receptor. Targeting this receptor may allow more selective immunosuppressive therapy. This antibody is used in islet transplantation
Side effects of antibody therapy
Syndrome of fever and myalgia that is believed to be caused by systemic release of cytokines
Also develop lymphomas
Lymphomas occur in _% of all recipients of transplanted organs
1-2
Immunosuppressive regimen
Multiple immunosuppressive drugs acting at different levels of T cell activation
Standard:tacrolimus and corticosteroid
__ antibodies are used in some centers before transplantation to prevent the activation of anti graft immune response
Antilymphocyte
Antilymphocyte antibodies are effective but increase the incidence of what
Lymphoproliferatice disorders and possibly infections
The administration of murine anti cd3 OKT3 is associated with what
Fever, chills, hypotension, pulmonary edema, encephalopathy, nephropathy…CAPILLRARY LEAK SYNDROME
Complications of immunosuppressive regimen
Infections, malignancies, bacterial fungal viral
Frequent agents of infection after transplant
CMV, herpes virus, fungal organisms, Aspergillus, Nocardia, cryptococcal, pneumocystis, toxoplasmosis
What is the most frequent and pathologically important post transplant infection
CMV
Does cmv infection last for life
Ya latent
When does cmv deactivate
Impaired T cell immunity
Primary cmv infection
If in organ that was transplanted
In renal, cardiac, lung, liver and bone marrow transplant, CMV causes what
Fever, leukopenia, hepatitis, pneumonia is, oesophagitis, gastritis, colitis, 1month after surgery
CMV retinitis can appear later
Ok
How treat cmv infection
Ganciclovir, a guanosine derivative
What are the most common cancers seen after organ transplant
Lymphoma, skin cancer, Kaposi Sarcoma
The development of __ diseases is also dependent on immunosuppression, induced by drugs such as ciclosporin, tacrolimus, okt3
Lymphoproliferative
In the setting of allotransplatation , lymphoproliferative diseases are aggressive with a high incidence of what
Central nervous system and extranodal involvement ; they are mainly classified as B cell derived large cell non Hodgkin lymphomas and can be polyclonal or monoclonal
Outcome os lymphoproliferative disease
Poor unless immunosuppressive therapy can be stopped
Origin of these lymphoproliferative diseases has been ascribed to the effect of the oncogenic ___ over B cells constantly stimulated by the allograft. Immusuppression would be a catalyst
EBV
The use of immunosuppression controls rejection episodes
The introduction of ciclosporin a in the 1980s has dramatically improved the outcome of allotransplantation
Immunosuppressive regimens typically include and use multiple drugs acting at different levels of what
T cell activation
Episodes of rejection resistant to conventional immunosuppressive regimens are controlled by what
Use of high dose steroids, tacrolimus, and antilymphocyte antibodies
Side effects of immunosuppression
Opportunistic microorganisms and malignancies