Transplantation

Question 1

Alloimmunity

Answer 1

Immune response due to different/other tissue of the same species.

Question 2

3 immune responses to genetically dissimilar tissue

Answer 2

1. Transient neonatal alloimmunity
2. Transfusion reactions
3. Transplant rejection

Question 3

Transient neonatal alloimmunity

Answer 3

Fetal Ag/Maternal Ab

• Hemolytic disease of the newborn
• Neonatal alloimmune Thrombocytopenia

Maternal autoimmune disease

Question 4

When is hemolytic disease of the newborn of concern

Answer 4

If mom is - and dad is + and then baby is positive.
Concern after first birth. After the placenta has pulled away from uterine walls and the mom’s body has been exposed to fetal blood.

Question 5

What medication to take to prevent HDTN

Answer 5

Rhogam. Administer twice.

Question 6

Neonatal alloimmune thrombocytopenia

Answer 6

Low levels of thrombocytes (platelets)
Like HDN, only with platelets
Up to 60% of cases occur during first pregnancy.
Mortality 10%. Usually do not screen for this.
Resolves in 2-3 weeks without treatment.
Involves IgG from mom that degrade over time.

Question 7

Transient neonatal alloimmunity caused by maternal autoimmune disease

Answer 7

Material antibodies can cross the placenta (type II) and react with material Age that are in the fetus. Elicit an immune response.
Effects are usually transient.

Seen in maternal patients with SLE, Myasthenia gravis, and graves.

Question 8

Antigens on red blood cells

Answer 8

Carbohydrate antigens. Individuals produce Abs to blood type antigens they lack.

Question 9

ABO incompatibility results in which hypersensitivity response

Answer 9

Type II by complement mediated lysis.

Question 10

Organ transplant criteria

Answer 10

1. Irreversible organ damage
2. No alternative treatment options
3. Non recurring disease. Infection? ok. But HSK? no, will continue to flare up over time.
4. Transplant compatibility
   - Priority based on organ needed
   - ABO compatibility
   - Haplotype matching (arrangement of genes on Chr)

Question 11

HLA Class I molecules

Answer 11

HLA A, B , and C

Question 12

HLA Class II molecules

Answer 12

HLA DR (most important to match! Less flexible)
HLA DQ
HLA DP

Question 13

Siblings with same parents have __ % chance of having matching haplotypes

Answer 13

20%

Question 14

Minor HLA differences

Answer 14

Associated proteins from the donor with different amino acid sequences. Encoded by genes outside HLA region Not detected by standard tissue typing techniques.
Can cause graft rejection in up to 1/3 of transplants.

Question 15

Transplant rejection is mediated by?

Answer 15

Cells mainly.

Question 16

How are transplant rejections classified?

Answer 16

According to time

Hyper acute: Minutes to hours
Acute: First days to weeks
Chronic: years

Question 17

5 causes of transplant rejection

Answer 17

MHC I 
MHC II 
ABO 
Endothelial antigens 
Minor HLA

Question 18

What causes hyper acute transplant rejection?

Answer 18

Pre-existing host serum ABs specific for alloantigens.
Ag-Ab complex settles in donated tissue activating PPS= leukocyte infiltration = blood clots = ischemia = “white graft”

Preventable with careful ABO and HLA matching.

Maybe seen in patients with history of many transplants or women who have been pregnant with many different men. Exposed to lots of non-self Ags.

Question 19

What causes acute transplant rejection?

Answer 19

Mismatched HLA antigens. Leads to activation of T cells by Cell mediated (90%) or humoral destruction (10%)

Cell mediated: Recepient T cells directed at the MHC on donor cell antigen presenting cells. Can be minimized with immunosuppressants. Damage to endothelial cells is reason for rejection.

Humoral destruction/ Ab mediated: Ab against HLA antigens. B cells and complement activated. Causes clotting in recipient blood vessels.

Question 20

What causes chronic transplant rejection?

Answer 20

Humoral and cell mediated (mechanism poorly known)

Proliferation of fibroblasts and vascular cells cause slow loss of organ function.

Result in arteriosclerosis of donor vessels- thickening due to collagen deposit.

Question 21

Graft vs host disease

Answer 21

Side effect of bone marrow or cord blood transplant. Major HLA is matched, but minor HLA is not matched and causes antigens.
Treat by immunosuppressant therapy.

Question 22

Cornea transplant survival %

Answer 22

90

Question 23

____: Clinical goal of transplantation

Answer 23

Tolerance. Host tolerating foreign tissue..

Question 24

What is the role of immunosuppressant drugs?

Answer 24

Allow for imperfect matches.
Important in controlling the MHC antigen rejection.
Bad bc it can dampen appropriate immune responses.

Question 25

Anterior chamber associated immune deviation (ACAID) in cornea transplants

Answer 25

Before transplant, intentionally trigger an immune response in the anterior chamber by sticking a needle with Ag to increase T cells. AS response, body will suppress immune response because they don’t want immune cells in the eye.

Question 26

Key risk factor in cornea transplant

Answer 26

Corneal vascularization.

Question 27

What is the line of rejection in a cornea transplant

Answer 27

A line of actual immune cells. Usually along with corneal edema and vascularization.

Question 28

Future of transplantation

Answer 28

Xenotransplantation- between species.
regenerative medicine using stem cell
Artificial organs by biomedical replacement