transplantation

Question 1

define Rejection

Answer 1

refers to damage done by the immune system to a transplanted organ

Question 2

define Autologous transplant

Answer 2

refers to tissue returning to the same individual after a period outside the body, usually in a frozen state

Question 3

define Syngeneic transplant

Answer 3

refers to transplant between identical twins; there is usually no problem with graft rejection. Also called isograft

Question 4

define Allogenic transplant

Answer 4

takes place between genetically non-identical members of the same species; there is always a risk of rejection

Question 5

define Cadaveric transplantation

Answer 5

uses organs from a dead donor

Question 6

define Xenogeneic transplant

Answer 6

takes place between different species and carries the highest risk of infection

Question 7

what is the criteria for solid organ transplant

Answer 7

• There must be good evidence that the damage is irreversible
• That alternative treatments are not applicable
• The disease must not recur

Question 8

The main problem with all solid organ transplants is the risk for rejection, how can this be minimised

Answer 8

This risk can be minimised by performing the following:

• The donor and recipient must be ABO compatible
• The recipient must not have anti-donor HLA antibodies
• The donor should be selected with as close as possible HLA match to the recipient
• The patient must take immunosuppressive treatment

Question 9

what are the different types of rejection

Answer 9

hyperacute, acute, chronic

Question 10

what type of hypersensitivity reaction is acute rejection

Answer 10

type IV

Question 11

what is the difference in timing between hyperacute, acute and chronic rejection

Answer 11

hyperacute - couple of hours

acute - days or weeks

chronic - months/years

Question 12

what causes hyperacute rejection

Answer 12

pre-formed antibody against donor HLA or ABO antigens

Question 13

what causes acute rejection

Answer 13

newly synthesised T cells against donor

Question 14

what causes chronic rejection

Answer 14

multifactorial

Question 15

define tolerance in the context of transplantation

Answer 15

Tolerance can be defined as a state of unresponsiveness to molecules the immune system has the capacity to recognize and attack. In the context of transplantation, this means that there is no response to alloantigens present on the transplanted tissue, but responses to pathogens are not affected.

Question 16

discuss tissue typing and cross matching

Answer 16

Before most allogeneic transplants, it is desirable to ensure that the donor and recipient have as closely matched as possible HLA alleles. This comparison of HLA alleles is referred to as tissue typing.

The organ is transported on ice, along with a blood sample, to a hospital with a potential recipient with good HLA matches.

Then the blood sample from the donor is mixed with the recipient to check if the donor possesses any antibodies against donor antigens. This is termed cross-matching

Question 17

what criteria has to be satisfied by the recipient and donor (live/cadaveric) for a kidney transplant to take place

Answer 17

Question 18

define graft versus host disease

Answer 18

GVHD occurs when donor T cells respond to allogeneic recipient antigens. It occurs when there are mismatches in major or minor histocompatibility antigens.

Mostly occurs in bone marrow transplant

Question 19

how can GVHD be prevented

Answer 19

careful and very close tissue matching

deplete donor marrow of T cells in-vitro prior to grafting

Question 20

problems with xenografting from pigs is that humans already have IgM antibodies against pig antigens. What are possible solutions t this problem

Answer 20

1. remove the IgM antibody ex vivo from potential pig organ recipients
2. genetically modified (silenced) pigs
3. humanised transgenic pigs (chimeras)