Major Histocompatability Complex And Rransplantation Immunology

Question 1

Major Histocompatibility Complex (MHC)

Answer 1

Surface proteins on cells that are important for the distinction of self or foreign molecules

Question 2

Primary immune cell for infections

Answer 2

T-cells
The NK cells will target those lacking MHC

Question 3

Which cells have MHC on they’re surfaces?

Answer 3

Nucleated cells and antigen presenting cells
They present peptides bound to MHC

Question 4

What is the major role of MHC?

Answer 4

To bind small antigenic peptides on the cell surfaces where they can be recognized by T cell receptors

Question 5

MHC genes

Answer 5

Encode MHC proteins (leukocyte antigens) expressed on cell surfaces
Ex: Human LA, Bovine LA, Swine LA

Question 6

Autograft

Answer 6

Transplant between organs within the same individual

Question 7

Allograft

Answer 7

Transplant between individuals of the same species

Question 8

Xenograft

Answer 8

Transplant between individuals of diff species

Question 9

Isograft/syngraft

Answer 9

Transplant between clones or inbred strains
Ex: Between identical twins

Question 10

Relationship between MHC and transplants

Answer 10

Host recognizes diff foreign MHC antigens on grafted tissues and ,mounts an immune response —> rejection

Question 11

Graft tissue process for graft rejection

Answer 11

1. Recipient blood flows through graft
2. Entering T cells encounter MHC 1, 2 and peptides on graft (leading to activation)
3. Antigen presenting cells encounter grafted cells, damaged cells, cytokines, etc (activation)
4. If blood group different Abs encounter BVs and Ags (antigen-antibody reacton)

Question 12

Host/ recipient process for graft rejection

Answer 12

1. Grafts APCs migrate to draining LNs
2. APCs encounter T cells reactive against graft
3. APCs attacked

Question 13

Blood types must match to prevent ______________

Answer 13

Hyperacute rejection

Question 14

Hyperacute rejection

Answer 14

Happens in minutes to 48 hours
Happens when preexisting Abs react
Immediate thrombosis and vascular destruction

Question 15

Accelerated rejection

Answer 15

Within a week
Cell mediated recognition of foreign MHC graft cells

Question 16

Acute Rejection

Answer 16

Within weeks
Most celll-mediated

Question 17

Chronic rejection

Answer 17

Within months
Both Abs and cells involved

Question 18

How do you prevent allograpft rejection?

Answer 18

Match for compatibility
Dogs and cats reject renal allografts within 6-30 days if not treated with drugs to suppress rejection

Question 19

What drugs prevent allograft rejection?

Answer 19

Azathioprine (prevent cell replication, DNA/RNA synthesis)
Cyclosporine (lymphocyte signaling and cytokine repsonse)
Prednisolone

Question 20

Immunosuppression makes patients susceptible to infection like ___________

Answer 20

opportunistic pathogens

Question 21

When are xenografts possible?

Answer 21

In biomedical research on immuno-deficient mice that lack T or B cells
Genetically engineered pigs
Pig and bovine heart valves

Question 22

Graft-Versus-Host Disease (GVHD)

Answer 22

When the recipient patient has no immune reaction to destroy the grafted immune-potent cells and grafted cells destroy the host

Question 23

When does GVHD occur?

Answer 23

When bone barrow replacement is given, grafted cells proliferate and occupy the host

Question 24

How is sperm not rejected?

Answer 24

Seminal plasma is immunosuppressive
Prostatic fluid inhibits complement activation

Question 25

Why SHOULD the fetus be rejected?

Answer 25

Fetus half non-self
Paternal MHC molecules are expressed and placenta lodges deep into uterus wall
Uterus perse not a privileged site
Mother-fetus may have different blood group Ags

Question 26

Why is the fetus not rejected?

Answer 26

Lack of polymorphic MHC molecule expression
Non-polymeric MHCs silence NK cells
T-reg cells abundant
Abundant immunosuppressive molecules prevent lymphocyte activation
Some maternal abs coat and protect placenta
Close balance maintained

Question 27

Privileged sites

Answer 27

Organs/ tissues where survival of foreign grafts may be prolonged or where immune responses are inhibited, suppressed or subverted

Question 28

Which tissues/ organs are privileged sites?

Answer 28

Cornea/eye, testis, brain, pregnant uterus

Question 29

How are there privileged sites?

Answer 29

Deficient lymphatic drainage
Physical barriers
Specialized epithelial or endothelial cell barriers
Locally operating immunosuppressive factors

Question 30

Cross-matching

Answer 30

Step to check if there are pre-existing Abs in the donor product or in recipient serum/ plasma

Question 31

Which species don’t require a cross match the FIRST time?

Answer 31

Dogs/ horses because they don’t naturally pre-exist (don’t do it the second time)

Question 32

Major crossmatching

Answer 32

Test if the recipient already has Abs to the RBCs that will be transfused
Check RBC from donor against serum from recipient

Question 33

Minor crossmatching

Answer 33

Test if the donor blood product/ serum has Abs against recipient RBCs
Check serum from donor against RBC from recipient