Immuno - Immune Responses (Grafts & Transplant rejection)

Question 1

What is the origin of an autograft?

Answer 1

From self

Question 2

What is the origin of a syngeneic graft?

Answer 2

From identical twin or clone

Question 3

What is the origin of an allograft?

Answer 3

From nonidentical individual of same species

Question 4

What is the origin of an xenograft?

Answer 4

From different species

Question 5

What are 4 types of transplant rejection? List them in order of increasing time to onset. What is the timing of onset for each?

Answer 5

(1) Hyperacute (within minutes) (2) Acute (weeks to months) (3) Chronic (months to years) (4) Graft-versus-host disease (Varies)

Question 6

Describe the pathogenesis of hyperacute transplant rejection.

Answer 6

Pre-existing recipient antibodies react to donor antigen (type II reaction), activate complement

Question 7

What are the 2 types of acute transplant rejection? Describe the pathogenesis for each.

Answer 7

Cellular: CTLs activated against donor MHCs; Humoral: similar to hyperacute, except antibodies develop after transplant

Question 8

Describe the pathogenesis of chronic transplant rejection. What are the components of this response?

Answer 8

Recipient T cells perceive donor MHC as recipient MHC and react against donor antigens presented. Both cellular and humoral components.

Question 9

Describe the pathogenesis of graft-versus-host disease in transplant rejection.

Answer 9

Grafted immunocompetent T cells proliferate in the immunocompromised host and reject host cells with “foreign” proteins –> severe organ dysfunction

Question 10

What is a characteristic feature of the hyperacute transplant rejection? What is the fate of the graft?

Answer 10

Widespread thrombosis of graft vessels –> ischemia/necrosis; Graft must be removed.

Question 11

What is a characteristic feature of the acute transplant rejection?

Answer 11

Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate.

Question 12

What effect do immunosuppressants have on acute transplant rejection?

Answer 12

Prevent/reverse with immunosuppression.

Question 13

What are 4 organ specific features characteristic of chronic transplant rejection?

Answer 13

Organ specific: (1) Heart - atherosclerosis (2) Lungs - bronchiolitis obliterans (3) Liver - vanishing bile ducts (4) Kidney - vascular fibrosis, glomerulopathy

Question 14

Is chronic transplant rejection reversible or irreversible? What mediates the damage that it causes?

Answer 14

Irreversible. T-cell and antibody-mediated damage.

Question 15

What are 4 symptoms associated with graft-versus-host disease?

Answer 15

(1) Maculopapular rash (2) Jaundice (3) Diarrhea (4) Hepatosplenomegaly

Question 16

In what 2 types of transplants does graft-versus-host disease usually occur, and why?

Answer 16

Usually in bone marrow and liver transplants (rich in lymphocytes)

Question 17

In what clinical context may graft-versus-host disease be potentially beneficial?

Answer 17

Potentially beneficial in bone marrow transplant for leukemia (graft-versus-tumor effect).