Introduction to the Immunology of Transplants and Tumors

Question 1

What is a syngeneic graft?

Answer 1

A genetically identical graft so it is easily accepted; rare only in identical twins

Question 2

What is an allogeneic graft?

Answer 2

Same species with genetic differences; they are rejected by the immune system at different extents

Question 3

What is a xenograph?

Answer 3

Different species organ graft

Question 4

What are the three mechanisms of rejection?

Answer 4

Hyperacute; acute; chronic

Question 5

What is an alloantigen?

Answer 5

Primary target of rejection: MHC (HLA) proteins class I and class II

Question 6

What are xenoantigens?

Answer 6

Targets of rejection in a xenograph typically endothelial cell antigens and blood cell antigens

Question 7

What is the timing for a hyperacute rejection?

Answer 7

Within minutes of transplantation

Question 8

What is the culprit in hyperacute rejection?

Answer 8

Pre-existing circulating antibodies specific for graft antigens

Question 9

What is the clinical significance in hyperacute rejection?

Answer 9

The major barrier in xenotransplantation; not a big issue in donor/recipient testing

Question 10

What is the timing for a acute rejection?

Answer 10

Within days or weeks of transplantation

Question 11

What is the culprit in acute rejections?

Answer 11

Immune response against graft alloantigens (CD8+ CTLs, CD4+ T cells)

Question 12

What is the clinical significance of acute rejection?

Answer 12

Causes major organ rejection but can be prevented/curbed by immunosuppressive therapy

Question 13

What is the timing for chronic rejection?

Answer 13

Occurs over months or years after transplant

Question 14

What is the culprit in chronic rejections?

Answer 14

Immune response against graft alloantigens, chronic inflammatory reaction (CD4+ T cells)

Question 15

What is the clinical significance of chronic rejection?

Answer 15

Causes major problem; not affected by immunosuppressive therapy

Question 16

What is immune surveillance?

Answer 16

The idea that the immune system can control and eliminate malignant cells

Question 17

What is a tumor antigen?

Answer 17

An antigen expressed only on malignant cells not on normal cells; may be recognized by immune system as a foreign antigen

Question 18

What is the primary mechanism of immune mediated tumor rejection?

Answer 18

Dendritic cell engulf and presents antigen to CD8+ CTLs specific for tumor antigen there is then a normal immune response against the antigen

Question 19

What are three anti-tumor immunotherapy strategies?

Answer 19

Passive immunity

2 Types of active immunity

Question 20

How is passive immunity used in anti-tumor therapy?

Answer 20

Tumor-antigen specific T cells removed from patient and expanded in vitro and transferred back; Monoclonal antibodies specific for tumor antigen transferred to the patient

Question 21

How are vaccines used against tumors?

Answer 21

Dendritic cells are loaded with tumor antigens and then injected into the patient, the dendritic cells present to tumor specific T cells activating them against tumor cells

Question 22

How are monoclonal antibodies used against tumors?

Answer 22

Monoclonal antibodies specific for inhibitory receptors on T cells are injected (CTLA-4 and PD-1) The antibodies then bind the inhibitory sites activating tumor-specific T cells that attack the tumor