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Immunology 436 > Ch. 19 Transplantation > Flashcards

Ch. 19 Transplantation Flashcards

1
Q

What’s an autograft?

A

Transplant from one area to another area of same individual

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2
Q

What is an isograft

A

Transplant from one to another that are genetically identical

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3
Q

What is an allograft?

A

Transplant between 2 of organisms of same species with DIFFERENT MHC self-antigens. Results in rejection, nonhistocompatible

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4
Q

What is a xenograft?

A

Graft between donor and recipient of different species. Histoincompatible

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5
Q

Which transplant is more flexible? Allograft or xenograft?

A

Allograft

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6
Q

What are other names for isograft?

A

Syngraft or symgraft

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7
Q

List the type of transplants from most to least durable

A

Autograft = isograft > allograft > xenograft

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8
Q

Which sugar is found in pigs but not humans?

A

GGTA (alpha 1,3 galactosyltransferase)

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8
Q

Which sugar is found in pigs but not humans?

A

GGTA (alpha 1,3 galactosyltransferase)

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9
Q

What happens during hyperacute rejection of transplanted pig organ cells in humans?

A

Human antibodies bind to GGTA sugar molecules on the surface of the pig cells

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10
Q

How did scientists bypass hyperacute rejection of pig organ transplants?

A

GGTA knockout pigs!

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11
Q

Describe first-set rejection of skin transplants

A

T cells activate. Skin appears normal for 2 weeks, then sloughs off several days later

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12
Q

Describe second-set rejection of skin transplants

A

Memory T cells activate. Skin is rejected within 6-8 days. Caveat: if skin from a different MHC mouse, the recipient immune system follows first-set rejection kinetics

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13
Q

Contrast first-set acute rejection at 5 days to second-set rejection at 7 days

A

Good vascularization and cell division in first-set VS no vascularization in second-set rejection

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14
Q

Describe the histological results of organ rejection

A

-lymphocyte and monocyte infiltration characteristic of DTH
-Both CD4 and CD8 T cells present

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15
Q

What is DTH?

A

delayed-type hypersensitivity (Type IV)

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16
Q

What condition manifests in humans without T cells? What causes this condition?

A

DiGeorge syndrome is caused by a hypoplastic thymus, meaning that T cell development failed

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17
Q

How do you slow down or prevent organ rejection?

A

Immunosuppressive drugs

18
Q

Describe hyperacute rejection (time, antibodies, type of immunity)

A

-Occurs within minutes to hours
-Preformed Ab to incompatible MHC Ag from previous transplants, transfusions, or pregnancies, activate complement, platelet activation factor, and platelet activation
-Cell-mediated immunity NOT a factor

19
Q

Describe why pregnancies are immunologically possible

A

The fetus is considered an “Ag” or “allograft” because can have incompatible MHC, so mom makes anti-MHC antibodies against dad’s MHC. HLA-G binds with KIR of NK cells, so they don’t kill fetal cells. Alpha-fetoprotein is an immunosuppresant that also helps fetal survival. Fetus expresses complement inhibitory protein. NO MHC II in placenta

20
Q

Describe acute rejection (time, what type of recipient, mediated by which cells…etc)

A

-May begin a few days after getting kidney, with complete rejection within 10-14 days
-Occurs in recipient that has NOT been previously sensitized
-Mediated by T cell activation
-Occurs in people with mismatched tissue
-First-set rejection timeline

21
Q

Consequences of acute kidney rejection?

A

-Enlargement and tenderness
-Reduced urine output
-Reduced renal blood flow
-Cell-mediated immunity with lymphocyte and macrophage infiltration

22
Q

Describe chronic rejection (time, mediated by which immune system, kidney example…etc)

A

-Occurs over the span of months-years
-Environmental insult stimulated rejection
-Mediated by both Ab and cell-mediated immunity
-Proliferative inflammatory lesions of small arteries, interstitial fibrosis (scarred lungs)
-kidney example: slow renal failure

23
Q

MHC stands for what? What was it’s old name?

A

Major histocompatibility complex. Used to be HLA (human leukocyte antigen)

24
Q

Describe structural composition of MHC I

A

One alpha chain composed of A, B, or C. Also have beta chain (b2 microglobulin)

25
Q

What is the role of the alpha chain in MHCI?

A

Ag presentation and immune response

26
Q

What is the role of the beta chain in MHC I?

A

Location

27
Q

What percentage of T cells are activated against MHC I after transplant?

A

5% (super high)

28
Q

Which molecular component of MHC II must match between donor and recipient?

A

HLA D

29
Q

Why are transfusions sometimes done before a transplant?

A

It introduces tolerance/desensitization

30
Q

In allograft rejection, the immune response is mounted against which molecule?

A

MHC I

31
Q

Name the types of MHC loci

A

Class I: HLA-A, B, and C
Class II: HLA -DP, DQ, and DR

32
Q

Which MHC loci are cause for concern in potentially rejecting allograft?

A

HLA-A, B, or C

33
Q

Describe the direct method of CD4 or CD8 T cell alloantigen recognition

A

APC from donor confuses host T cells into getting activated because they recognize the foreign MHC proteins

34
Q

Describe the indirect method of CD4 or CD8 T cell alloantigen recognition

A

Recipient APC processes donor Ag and presents it to T cells. Often leads to Ab against donor tissue

35
Q

Explain time details for blood transfusions to prep recipient for transplant

A

1-2 week intervals. 100-200 ml whole blood from donor

36
Q

List the 3 drugs that block T cell proliferation and thus lead to immunosuppression

A

Cyclosporin A, FK506, and rapamycin

37
Q

How do cyclosporin A and FK506 cause immunosuppression?

A

Block calcineurin phosphatase, which blocks IL-2 production. IL-2 normally activates T cells

38
Q

How does rapamycin cause immunosuppression?

A

Blocks signal transduction after IL-2 binds IL-2 receptor

39
Q

Which fetal cells do not express MHC I or II? Where are they found?

A

Trophoblasts. Found on outer layer of placenta. Do not prime mom’s immune system

40
Q

Which protein do fetal trophoblasts express? Why do they not activate mother’s immune response?

A

MHCIb. They bind NK KIR, thus blocking NK cell activation. No fetal cell killing

41
Q

Which proteins does the placenta not express?

A

MHC I with A, B, or C

42
Q

List immunologically privileged sites. Why are they privileged?

A

-Fetus: explained earlier
-Corneal grafts: no HLA-D regions, blood and lymphatic circulation in cornea is minimal
-Brain: Most Ag in CSF generate B cell response, so more dangerous T cell response is avoided
-Testes: Sertoli cell barrier isolate sperm inside testes so host Ab can’t reach them

Immunology 436 (11 decks)

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