Transplantation

Question 1

What is the key barrier to transplant success?

Answer 1

The recipient’s immune system recognises the graft as non-self and mounts an immune response

Question 2

What is an autologous graft?

Answer 2

Transplant from the same individual

Question 3

What is an allograft?

Answer 3

Transplant between genetically different individuals of the same species

Question 4

What is a xenograft?

Answer 4

Transplant between different species

Question 5

What is a syngeneic graft?

Answer 5

Transplant between genetically identical individuals

Question 6

What molecules are primarily responsible for graft rejections?

Answer 6

• MHC molecules
• HLA molecules

Question 7

What are the three classes of MHC I?

Answer 7

• HLA-A
• HLA-B
• HLA-C

Question 8

What are the three classes of MHC II?

Answer 8

• HLA-DP
• HLA-DQ
• HLA-DR

Question 9

Why is HLA matching difficult?

Answer 9

At HLA genes are highly polymorphic

Question 10

What are the three main T cell allorecognition pathways?

Answer 10

• Direct
• Indirect
• Semi-direct

Question 11

What is the direct T cell allorecognition pathway?

Answer 11

Recipient T cells recognise donor MHC directly

Question 12

What is the indirect T cell allorecognition pathway?

Answer 12

Recipients antigen presenting cells present donor peptides to T cells

Question 13

What is the semi-direct T cell allorecognition pathway?

Answer 13

Donor MHC peptides incorporated into recipient antigen presenting cell membranes

Question 14

What are minor histocompatibility antigens?

Answer 14

Non-HLA proteins that can cause rejection even in HLA matched transplants

Question 15

What is hyperacute rejection?

Answer 15

• Rejection that occurs within minutes to hours
• Mediated by preformed antibodies

Question 16

What is acute rejections?

Answer 16

• Rejection that occurs within days to weeks
• Mediated by CD8+ and CD4+ T cells and antibodies which attack the graft

Question 17

What is chronic rejection?

Answer 17

• Rejection that occurs over months to years
• Driven by CD4+ T cells and sometimes antibodies

Question 18

What is HLA typing?

Answer 18

Histocompatibility testing to identify HLA alleles for matching

Question 19

What are DSAs and why are they screened?

Answer 19

Donor specific antibodies against allo-MHC

Question 20

What is a lymphocyte cross match?

Answer 20

A test to detect recipient antibodies that react with donor HLA

Question 21

What is the chance of siblings being HLA identical?

Answer 21

25%

Question 22

What is the chance of siblings sharing one haplotype of HLA?

Answer 22

50%

Question 23

What is the chance of siblings sharing none of HLA?

Answer 23

25%

Question 24

What is induction immunosuppression therapy?

Answer 24

Administered at transplant to block T cell activity

Question 25

What is maintenance immunosuppression therapy?

Answer 25

Long term immunosuppression to prevent rejection

Question 26

What is operational tolerance?

Answer 26

Stable graft function without ongoing immunosuppression

Question 27

When has tolerance been achieved in practice?

Answer 27

- Up to 20% of liver transplants - Some kidney + bone marrow transplants

Question 28

What is the role of Tregs in tolerance?

Answer 28

Tregs can suppress alloreactive responses and promote tolerance

Question 29

What are the four main ways to prevent rejections?

Answer 29

- Blood typing - Screening for donor specific antigens - Close HLA match - Immunosuppression