Lecture 19 - Transplant

Question 1

Define transplantation.

Answer 1

The act of transferring cells, tissue, or organs from one site to another.

Question 2

What is a graft?

Answer 2

An implanted cell, tissue, or organ.

Question 3

What is a donor? What is a recipient or host?

Answer 3

An individual who provides the graft.
Individual who receives the graft.

Question 4

Define autograft.

Answer 4

When self tissue is transferred from one body site to another.

Question 5

Is the immune system elicited when autograft is present? Explain.

Answer 5

No because antigen present in autograft is same as that present in body, so the immune system recognizes the autograft antigen as a self antigen.

Question 6

Give examples of autograft surviving out of the life.

Answer 6

Transferring healthy skin to burned area, use of healthy blood vessels to replace blocked coronary arteries, and plastic surgery of skin.

Question 7

Define isograft. Also called what?

Answer 7

A tissue or organ transplant between genetically identical individuals of the same species.
Also called a syngraft.

Question 8

Why does the graft survive in isografts? Give an example.

Answer 8

Because the histocompatibility antigens are identical.
Ex. b/w twins

Question 9

Define allograft.

Answer 9

Tissue is transferred between 2 genetically different members of the same species.

Question 10

Does the immune response elicit a response for allografts?

Answer 10

Yes because in allograft histocompatibility antigens are dissimilar hence immune response is elicited and graft is rejected.

Question 11

Define xenograft. Give an example.

Answer 11

Tissue is transferred between 2 different species.
Ex. Graft of human transferred to an animal.

Question 12

Are xenografts rejected?

Answer 12

Yes, the histocompatibility complex antigens are so different that the graft is more vigorously rejected.

Question 13

What are the 2 types of alloantigen recognition?

Answer 13

Direct and indirect alloantigen recognition.

Question 14

What is the difference between direct and indirect alloantigen?

Answer 14

Direct: Host T cells recognize intact allo-MHC molecules on the surface of the donor cell.
Indirect: Donor MHC is processed and presented by recipient APC.

Question 15

What are the 3 classifications of allograft rejections based on histopathological features?

Answer 15

Hyperacute rejection, acute rejection, and chronic rejection

Question 16

What happens in hyperacute rejection?

Answer 16

Graft is rejected within minutes to hours because vascularization is rapidly destroyed.

Question 17

Hyperacute rejection involves 5 main steps.

Answer 17

1. Preformed antibody,
2. Complement activation,
3. Neutrophil margination,
4. Inflammation,
5. Thrombosis formation

Question 18

What happens in acute rejection?

Answer 18

When vascular and parenchymal injury mediated by T cells and antibodies that usually begin after the first week of transplantation if there is no immunosuppressant therapy .