Transplantation Immunology

Question 1

Transplantation

Answer 1

potentially lifesaving treatment for endstage organ failure, cancers, autoimmune diseases, immune deficiencies etc

Question 2

Transplantation Immunology

Answer 2

sequence of events that occurs after an allograft or xenograft is removed from donor & then transplanted into a recipient

Question 3

Organ Transplants

Answer 3

introduce foreign tissues/cells into a host

immune system still intact!

Question 4

Hematopoietic cell Transplant

Answer 4

replacement of all blood/marrow cells

immune system is first depleted !

Question 5

Autologous grafts (autografts)

Answer 5

self-tissue transferred from one body site to another in the same individual
ex: skin graft on a burn patient

Question 6

Syngenetic gratfts (isografts)

Answer 6

tissue transferred between genetically identical individuals

Question 7

Allogeneic grafts (allografts)

Answer 7

tissue transferred between genetically different members of the same species
most transplants

Question 8

Xenogeneic grafts (Xenografts)

Answer 8

tissue transferred between different species

pig heart valves

Question 9

Transplant Complications

Answer 9

1. Hyperacute rejection
2. Acute cellular rejection
3. Chronic rejection

Question 10

Hyperacute Rejection

Answer 10

occurs w/in minutes to hours after vascular supply to the transplanted organ is established
ABO, HLA antigens elicit the reaction - leads to necrosis of the tissue
this is seldom encountered due to testing

Question 11

Crossmatching

Answer 11

tests a recipient’s serum against prospective donor’s cells (WBCs) to determine if donor specific antibodies (DSAs) are present

Question 12

Acute Transplant Rejection

Answer 12

develop days to weeks after transplant

cellular type rejection involving CD8+ T cells ( Type IV delayed hypersensitivity)

Question 13

Chronic Rejection

Answer 13

slow but continual loss of organ function over months or years
multi-factorial
most transplanted organs will be rejected in time

Question 14

Testing for Chronic Rejection

Answer 14

screen for antibodies in the serum against HLA class 1 & 2 proteins
key reagent - latex beads coated with various class 1 or 2 antigens

Question 15

Hematopoietic Cell Transplant

Answer 15

most difficult
entire immune system is transferred
autologous transplant is best if malignancy doesn’t involve bone more or is not genetic

Question 16

3 sources of Hematopoietic Stem Cells

Answer 16

bone marrow
peripheral blood after ‘mobilization’
umbilical cord

Question 17

HCT processing

Answer 17

1. collection of stem cells from bone marrow or peripheral blood
2. processing - isolate, concentrate & prepare stem cells for storage
3. cryopreservation
4. chemotherapy
5. infusion of stem cells

Question 18

Neutrophil Engraftment

Answer 18

usually occurs within 14-20 days

absolute neutrophil count of 500/ul for 3 days in a row

Question 19

Platelet engraftment

Answer 19

20,000 platelets/ul
occurs after neutrophil engraftment
can take up to 2 months

Question 20

Graft Versus Host Disease (GVHD)

Answer 20

the infused products often contain some mature T cells which target the recipient (>90% mortality rate)

Question 21

Infections prior to neutrophil engraftment

Answer 21

viridens strep, enterococcus, enterobacteriaceae

2% due to Candida - high mortality rate

Question 22

Immunosuppressive agents

Answer 22

corticosteroids

IL-2 signaling blockers (Cyclosporin A, Tacrolimus, Everolimus)

Question 23

BK Virus

Answer 23

important cause of Kidney transplant failure (5-8%)
90% are infected by adulthood (asymptomatically)
re-emerges due to immune suppression