Transplant Immunology

Question 1

transplant rejection

Answer 1

• is the destruction of grafted tissue by the acquired immune system of the recipient host
• the immune response that destroys grafted tissue is directed at unique determinants that arise due to genetic differences between the donor and the recipient

Question 2

allogenic

Answer 2

describes individuals of the same species that are genetically different
genetic differences caused by polymorphisms

Question 3

Most polymorphic genes in the human genome

Answer 3

MHC class I and II genes

Question 4

T/F Blood group antigens have an effect on rejection

Answer 4

true

Question 5

autograft

Answer 5

graft of tissue from one part of the body to another part of the body
genetically identical and shouldn’t be rejected

Question 6

syngeneic graft

Answer 6

one in which the donor and the recipient are genetically identical (e.g. identical twins)
no rejection

Question 7

allograft

Answer 7

graft between two patients that are not genetically identical
there will be rejection unless immumnosuppresives are used

Question 8

zenograft

Answer 8

graft between 2 different species

Question 9

Allogenic solid tissue graft are rejected by ______

Answer 9

T cells specific for alloantigens on the transplanted tissue

Question 10

Graft vs Host Disease

Answer 10

-after bone marrow transplant sometimes T cells from the grafted bone marrow will attack alloantigens of the host
results in inflammatory responses of the skin and GI tract
-unlike an organ transplant rejection the T cells can potentially recognize targets all over the body of the recipient

Question 11

GVHD in solid organ transplant

Answer 11

can occur if mature naive T cells remain in the vasculature of the transplanted organ

Question 12

Blood transfusion tissue grafts

Answer 12

Do not involve T cells as RBC’s don’t express MHC class I or II. A and/or B group antigens are the primary target

Question 13

T/F Everyone expresses O anitgen?

Answer 13

True, O antigen is at the core for both A and B antigens

Question 14

T/F A person with type AB blood will not have antibodies specific for any of the blood group antigens in their circulation.

Answer 14

true

Question 15

Type O can transfuse into _____

Answer 15

ANYONE, universal donors

but can only receive type O blood

Question 16

Type AB individuals are _____

Answer 16

universal recipients

Question 17

Type A individuals can receive ___

Answer 17

Type O and A

Question 18

Type B individuals can receive ____

Answer 18

Type O and B

Question 19

Rh factor

Answer 19

expressed on the surface of RBCs
must be considered before transfusion
most important is RhD

Question 20

T/F There are no normal flora pathogens similar to Rh factor so unless an individual has had a prior transplant the body will not mount an immune response

Answer 20

true

Question 21

Rh neg

Answer 21

can only receive from Rh neg donors

Question 22

Rh positive

Answer 22

can receive from positive or negative donors

Question 23

hyperacute rejection

Answer 23

• is mediated by pre-formed antibodies that are specific for alloantigens that are expressed on the grafted tissue
• The most common cause of hyperacute rejection is transplantation of tissue from a donor whose blood type is not compatible with the recipient’s
• abs bind the A or B antigens expressed on the vascular epithelium of the donor tissue and initiate opsonization and complement leading to an inflammatory response and platelet adherence which results in occlusion of the small vessels of that tissue-effect is that the inflammatory response kills the tissue
• can be prevented by proper cross-matching of blood

Question 24

T/F vascular epithelium expresses the same blood group antigens as are on the individuals RBCs

Answer 24

true

Question 25

Type O individuals has

Answer 25

anti A and B antibodies

Question 26

Type A individual has

Answer 26

anti B antibodies

Question 27

Type B individual has

Answer 27

anti A antibodies

Question 28

Type AB individual has

Answer 28

no antibodies

Question 29

acute transplant rejection

Answer 29

- mediated by CTLs specific for alloantigens on the transplanted tissue - alloantigens of the tissue are most often the product of polymorphic genes-essentially MHC molecules - takes 11-15 days for rejection because the host has to prime an immune response

Question 30

first set rejection

Answer 30

- CTL mediated rejection that occurs 11-15 days after transplant - host has to prime immune response

Question 31

second set rejections

Answer 31

- CTL mediated rejection that occurs faster than first set (4-7 days) - occurs after individual has already primed a response to a previous transplant - mediated by memory T cells

Question 32

acute allograft transplant rejection mechanism

Answer 32

- APC's from the donor tissue migrate into the secondary lymphoid tissues of the host and because they express the MHC alloantigens of the donor a CTL response is primed - Recipient APCs will also take up pieces of grafted cells that have died and will be able to present determinants of the donor tissue to naïve T cells in the secondary lymphoid tissues

Question 33

T/F degree of matching at HLA-A, HLA-B, and HLA-DR loci appear to be the most important for a successful tissue transplant

Answer 33

true

Question 34

T/F anti-inflammatory drug regimens are also extremely important to the success of transplantation of any tissue that has allogeneic determinants

Answer 34

true

Question 35

minor histocompatibility antigens

Answer 35

- encoded within the MHC locus, responsible for rejection that occurs with identical MHC molecules - takes between 30 and 60 days in the absence of anti-inflammatory drugs

Question 36

T/F Liver transplants don't require HLA-matching but do require proper blood group matching

Answer 36

true

Question 37

Why do corneal transplants not require HLA-matching or anti-inflammatory drugs?

Answer 37

Bc the tissue is not vascularized so CTLs can't reach it. Therefore no hyper acute rejection

Question 38

Why is the fetus not rejected?

Answer 38

- placenta acts as a barrier keeping moms t cells out and does not express MHC molecules - the placenta and the uterine epithelium produce Th2 cytokines that down regulate cell-mediated immune responses

Question 39

Rhogam

Answer 39

- anti-RhD IgG antibodies - antibodies will rapidly bind to and cause the destruction of any fetal RhD-positive RBCs that get into the mother’s circulation, preventing the mom from making an anti-RhD response that would lead to IgG specific antibodies that could cross the placental barrier and affect the fetus

Question 40

erythroblastosis fetalis or hemolytic disease of the newborn

Answer 40

- an RhD negative mother carrying an RhD positive child who has made abs against the RhD factor in the childs blood will prime an IgG ab response that can cross the placental barrier and bind and destroy fetal RBCs - child also develops immune complex disease - enlargement of spleen and liver as well as petechial lesions due to the depletion of platelets that results from excessive platelet adherence to the walls of small blood vessels (mediated by macrophage derived TNF-alpha production).

Question 41

When should RhoGam be given

Answer 41

- give to a RhD neg mother with a RhD positive child who has a blood type compatible with hers - If child has a blood type not compatible with hers then if the childs blood gets into the mothers circulation then the mothers abs against the fetal blood will destroy the RBC's before the body primes an anti-RhD response

Question 42

symptoms of GVHD

Answer 42

1. macropapular skin rash 2. high bilirubin serum levels secondary to bile duct inflammation 3. diarrhea