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Haematology and Immunology > Transplantation > Flashcards

Transplantation Flashcards

1
Q

Definition of transplant

A

The replacement of tissues or organs that have undergone an irreversible pathological process which threatens the patients life or to a significant degree, considerably hampers their QoL

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2
Q

Types of graft

A

Xenograft
Allograft
Isograft
Autograft

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3
Q

What is a xenograft?

A

A transplantation from a donor of a different species from the recipient

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4
Q

What is an allograft?

A

A transplant from one person to another

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5
Q

What is an isograft?

A

A transplant between two individuals who are genetically identical i.e. monozygotic twins

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6
Q

What is an autograft?

A

A transplant from one point to another of the same individuals body

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7
Q

What is immune tolerance?

A

A state of unresponsiveness of the immune system to SELF

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8
Q

Two types of immune tolerance

A 
Central control (thymus) 
Peripheral control
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9
Q

What is involved in central control?

A

Inactivation of cells required for initiation of an immune response

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10
Q

What is involved in peripheral control?

A

Inhibition of expression of the immune response

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11
Q

Two classes of HLA

A

Class 1
- HLA- A,B,C
Class 2
- HLA- DR, DP, DQ

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12
Q

Where is class 1 of HLA found?

A

On all nucleated cells

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13
Q

What class of HLA is most important in rejection?

A

Class 2

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14
Q

What recognises class 1 HLA?

A

CD8 + / Tc cells

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15
Q

What recognises class 2 HLA?

A

CD4 + / Th cells

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16
Q

The major histocompatibility complex consists of…..

A

Human leukocyte antigen (HLA)

Chromosome 6

17
Q

Features of privileged sites

A

No sensitisation / no tolerance
No requirement for tissue matching
No immunosuppression

18
Q

Blood flow and immunity

A

If there is blood flow = immunity exposed

19
Q

What is graft rejection?

A

Occurs when transplanted tissue is rejected by the recipients immune system, which destroys the transplanted tissue

20
Q

Causes of transplant / graft rejection

A

ABO or HLA incompatible
Pre formed immunity (sensitisation)
Failed immunosuppression (including non compliance)
Infections / environmental triggers

21
Q

When can immediate rejection happen?

A

Within minutes

22
Q

Classes of rejection

A

Immediate
Acute
Chronic

23
Q

Pathology of immediate rejection

A

ABO/HLA antibodies
Complement activation damages blood vessels
Inflammation and thrombosis

24
Q

When does acute rejection happen?

A

Usually in 1st 6 months

25
Q

Pathology of acute rejection

A

Sensitisation phase
1. recognition
2. APC reaction
3. co stimulation
Pre sensitised T cells hasten the process
Can be a mix of cell and antibody mediated
Cellular infiltration of graft by Tc cells, B cells, NK cells and macrophages
Endothelial inflammation and parenchymal cell damage

26
Q

What is the commonest cause of graft failure?

A

Chronic graft failure

27
Q

When does chronic graft failure occur?

A

> 6 months

28
Q

Pathology of chronic graft failure

A

Antibody mediated with other innate components

Myointimal proliferation in arteries

29
Q

Treatment of rejection

A

Corticosteriods
Anti-thymocyte globulin
Plasma exchange

30
Q

Complications of transplantation

A 
Rejection 
Infection (including zoonotic) 
Drug side effects
Recurrence of original disease 
Surgical problems
Ethical problems
31
Q

Prevention of graft rejection

A

ABO matching
Tissue typing (Class I and II HLA)
Prophylactic immunosuppression
Humanised or silenced xenografts

32
Q

What is used for immunosuppression?

A 
Corticosteriods (prednisolone) 
- wide spread anti inflammatory 
Calcineurin inhibitors (tacrolimus)
- block IL-2 gene transcription 
Anti proliferatives (MMF)
- prevent lymphocyte proliferation
33
Q

What is graft vs host disease principally a problem of?

A

Bone marrow transplant

34
Q

Requirements for graft vs host disease

A

Immunocompetent cells in graft
Deficient recipient immunity
HLA differences between donor and recipient

35
Q

Prevention of graft vs host disease

A

Donor / recipient matching

Donor marrow T cell depletion

36
Q

Types of donors

A 
Living
- related / unrelated
- altruistic 
Deceased donor
- brain death (DBD)
- cadaveric death (DCD)
37
Q

Which types of donors have less rejection, are quicker, last longer and healthier and are easier to manage?

A

Living donors

Haematology and Immunology (18 decks)

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