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Infection And Immunity > Transplantation > Flashcards

Transplantation Flashcards

1
Q

Blood transfusion

A

Simplest transplanting clinical practice
Compatibility determined by:
-genetic diversity
-associated immunological response to non self

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2
Q

What is the ABO SYSTEM

A

Determined by single gene encoding glycosylation enzyme
Modifies cell surface antigen H

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3
Q

What are the alleles

A

Allele A MODIFIES H INTO A
Allele B TURNS H INTO B
ALLELE O encodes non functional enzyme- no modification

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4
Q

What do humans produce against carb structures and because of what?

A

IgM antibodies
Due to cross reaction with bacterial antigens

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5
Q

Why are blood transfusions not that good?

A

Not long lasting, acute treatment

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6
Q

Why are organ and bone marrow transplants better?

What is a constant barrier?

A

More immunological complex
Last longer
Allows patient to live healthy long life

Rejection is a main barrier to long term transplant survival

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7
Q

What is acute rejection?

A

Allografts start successful without immunosuppression but fail after 10-14 days

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8
Q

What is chronic rejection?

A

Effective immunosuppression let’s allografts last longer for years but do degrade overtime

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9
Q

What is hyper acute rejection

A

Xenografts rejected within hours

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10
Q

What is an autograft

A

A graft of tissue from one body site to another in the same person

Cells are autologous or synergic like skin graft

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11
Q

What is this? Transplant from an unrelated person of the same species sometimes called homograft

A

Allograft

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12
Q

What is this? Transplant using the same tissue of a different species. Cells or tissue are xenogenic such as using animal organs in humans

A

Xenograft

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13
Q

What features are these of-
animal is given a second allograft reject it even quicker

T cells from allografted mouse accelerate the rejection

Is mediated by MHC and T CELLS
Allograft isn’t rejected when put on naked mice

A

Acute rejection

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14
Q

What is this? Antigens that differ between members of the same species and generate alloreactive response

A

Alloantigens

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15
Q

I am the major source of alloantigens

A

MHC

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16
Q

We are the most polymorphic proteins
We provide the greatest source of diversity between donor and recipient

A

MHC PROTEINS

17
Q

What improves when you minimise mismatch at the MHC

A

Allograft outcome

18
Q

What is this? Antigen presenting cells such as APC and DENDRITIC cells present in the grafted tissue:
- migrate out of the graft and into the recipient lymph nodes
- they engage with recipient T CELLS

A

Direct allorecognition

19
Q

What becomes quickly present when there is a higher MHC mismatch

A

Alloantigens

20
Q

It needs me to recognise allo- MHC or PEPTIDE to break MHC Restriction

A

TCR

21
Q

I allow host T CELL to attack graft what am I

A

Direct TCR allo MHC

22
Q

Donor DC present in graft eventually dies but rejection persists which is a second mechanism

If donor DC is depleted form graft rejection happens
What is this?

A

Direct allorecognition

23
Q

Allogenic cells or molecules process directly by recipient APC and present to recipient T CELLS

T cells can’t attack graft directly
T cells activate macrophage causing inflammation and tissue damage
Can induce anti graft antibody response (alloantibodies)

WHAT AM I?

A

Indirect allorecognition

24
Q

What is this process:
1. Fragments of donor cell with allo MHC
2. DYING OR DEAD DONOR CELL
3. recipient CD4+ T CELL WITH specificity against donor. Allo MHC derived peptide in context of self MHC

  1. Recipient macrophage has ingested donor cell and is presenting allo MHC derived peptide on recipient MHC
  2. T CELL IS activated by the macrophage and in return T cell provides signal like IFN- GAMMA
  3. This activates the macrophage to go through respiratory burst and cytokines reproduction

ACTIVATED MACROPHAGE DAMAGE DONOR TISSUE

A

Indirect allorecognition

25
Q

Involves transfer of donor MHC to recipient APC

A

Semi direct allorecognition

26
Q

What is this:
CD8 cells from direct recognition attack graft directly

CD4 CELLS from direct recognition help B cells make anti graft antibodies against graft

Antibodies bound graft lead to destruction via complement and ADCC macrophage and NK cells and further antigen presentation

CD4 T CELLS from indirect recognition help macrophage become activated and damage tissue

A

Tissue damage

27
Q

T cells positively and negatively selected when they develop for those whose TCR bind to self MHC but don’t react to self peptide as T cell learn self from non self

T cells bind strongly to MHC that are eliminated

But transplanted tissues gives new molecules to T cell post thymic that haven’t been calibrated on foreign tissues

A

Why T cells are reactive to allo MHC

28
Q

Allo MHC. Peptide complex binds efficiently to some recipient TCRs triggers what

A

Triggers T cell activation

29
Q

What do I also need alongside TCR and allo MHC

A

Allo MHC PEPTIDE

30
Q

What is this transplantation called? Recipient immune system is remove to allow repopulation with donor derived HSC

A

Haematopoietic stem cell transplantation

31
Q

In haematological malignancies like leukemia and lymphoma
Or genetic diseases like congenital immunodeficiency

Bone marrow failure and high dose chemotherapy for solid tumours

  • patient has their endogenous HSC destroyed chemically or irradiation and the donor HSC is infused

This means the recipient is allogenic to donor HSC and resultant donor derived immune system

A

Graft versus host disease- fatal so managed by immunosuppression

Alloreaction benefits in graft versus leukemia

32
Q

Foetus and placenta genetically half mom and dad

50% foetal genes codes proteins foreign to dad includes MHC molecules

Foetus is called hemi allograft

A

Common allograft

33
Q

What is this? Foetal maternal interface ( trophoblast) doesn’t express MHC class 2 but low MHC class 1 and a special MHC CLASS 1 (HLAG INHIBIT NK CELLS)

LIMITS. Allo MHC reactions
Placenta has factors to suppress T cell effectors

Promotes inhibitory regulatory T CELLS (Treg)

Uterine tissue (maternal) has mechanisms to limit cell attraction via chemokiens

A

Foetal maternal tolerance

34
Q

Polymorphism in MHC can disrupt MHC-TCR interaction and peptide-TCR interaction due to constraints on the peptide

Some MHC alleles are “better” at presenting certain peptides Diversity at MHC provides selective advantage,

pathogens less likely to evade antigen presentation

A

MHC POLYMORPHISM

Infection And Immunity (8 decks)

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