L24, L26- Transplant Rejection

Question 1

define autograft

Answer 1

tissue moved from one location to another on same individual

Question 2

define isograft

Answer 2

(aka syngeneic)

-graft between identical twins

Question 3

define allogenic graft

Answer 3

tissue delivered between genetically different member of the same species

Question 4

define xenogeneic graft

Answer 4

tissue delivered between members of different species (eg. baboon heart into child)

Question 5

list the types of transplant rejections

Answer 5

• hyperacute (previous exposure, eg. Rh factor)
• acute (cellular, humoral)
• chronic

Question 6

transplant rejections utilizes (cellular/humoral) immunity via (2) pathway

Answer 6

1- both cellular and humoral

2- direct and indirect pathways (see other cards)

Question 7

describe the direct pathway in transplant rejection

Answer 7

1) APC from donor tissue presents through MHC-I and MHC-II
2a) MHC-I –> Tc cells (CD8) –> tissue damage
2b) MHC-II –> Th cells (CD4) –> complement activation –> macrophage activation (IFN-γ) –> tissue damage

Question 8

describe the indirect pathway

Answer 8

1) APC from donor tissue presents MHC-II
2a) Th cells (CD4) –> direct pathway
2b) Th cells (CD4) –> B lymphocyte activation –> plasma cell –> Igs –> tissue damage

Question 9

transplant rejection mechanisms:
-(1) are stimulated and transformed to create (2) to target endothelial cells

• (3) target endothelial cells and parenchymal cells
• (4) secrete CKs to illicit type (5) hypersensitivity

Answer 9

1- B lymphocytes –> plasma cells
2- Igs

3- Tc cells (CD8+)

4- Th cells (CD4+)
5- type IV hypersensitivity

Question 10

Hyperacute transplant rejections:

• (1) time of onset
• (2) mechanism
• (3) morphology

Answer 10

1- mins-hrs

2- preformed Abs bind graft endothelium

3- vascular thrombosis +/- necrosis

Question 11

Acute cellular transplant rejections:

• (1) time of onset
• (2) mechanism
• (3) morphology

Answer 11

1- days-wks, mos-yrs

2- T cells injure graft via Tc direct cytotoxicity and Th type IV hypersensitivity mechanism (direct pathway)

3- interstitial lymphocyte infiltrates w/ tubulitis +/- arteritis

Question 12

Acute humoral transplant rejections:

• (1) time of onset
• (2) mechanism
• (3) morphology

Answer 12

1- day-wks, mos-yrs

2- antidonor Abs against graft Ags via plasma cells (indirect pathway)

3- microcirculatory inflammation +/- arteritis, thrombosis

Question 13

Chronic transplant rejections:

• (1) time of onset
• (2) mechanism
• (3) morphology

Answer 13

1- mos-yrs, irreversible

2- T cells release CKs –> smooth muscle proliferation

3- arteriolosclerosis, ischemic atrophy, interstitial fibrosis (tissue death)

Question 14

(1) is monitored closely in transplant management. If too much (1), (2) can result; if too little (3) can result.

Answer 14

1- immunosuppression therapy

2- opportunistic infections, neoplasia

3- graft rejection, graft v host disease (GVHD)

Question 15

GVHD:

• (1) is required from donor tissue
• (2) from donor tissue reacts to (3), especially when host has (4) status
• most commonly occurs after (5) procedures

Answer 15

(graft versus host disease)
1- immuno-competence

2- T cells (Tc/Th, type IV hypersensitivity)
3- host Ags (seen as foreign)
4- immuno-compromised/depleted (eg. chemotherapy)

5- allogeneic bone marrow transplant

Question 16

GVHD, acute:

• (1) timeframe
• (2) consequences

Answer 16

(graft versus host disease)
1- <100 days

2- affects immune system; epithelia of skin, liver, GIT –> rash, jaundice, diarrhea

Question 17

GVHD, chronic:

• (1) timeframe
• (2) consequences

Answer 17

(graft versus host disease)
1- >100 days

2:

• cutaneous injury w/ destruction of skin appendages
• GIT strictures
• cholestatic jaundice (via hemolysis)
• thymic involution, lymphocyte depletion