Transplant Flashcards
What cells from the recipient are responsible for rejection of a transplant?
T cells
When a BM transplant takes place, what cells attack the recipient? Why? What is this called?
Donor’s T cells, because host doesn’t have their own immune system- GVHD
What is one of the reasons that MHC proteins are so highly polymorphic?
Might prevent accidental transplant (prevent one animal from transmitted a tumor into another)
What is a MHC?
Major Histocompatibility Complex; a set of three genes that produce the proteins seen on cells
What are blood antigens?
Polysaccharides on the surface of RBC
Does the body naturally make Ab against blood antigens not present on RBCs? to D Ag?
Naturally to blood antigens not present; only makes Ab to D Ag following exposure (such as during pregnancy)
What causes a hyperacute rejection?
When preformed antibodies from the recipient react with the host
What are examples of hyperacute rejection?
Mismatching blood type; if had a previous transfusion/transplant then could already have antibodies to other MHC Ag; if had a baby then could have Ab to the MHC from the child
How quickly does a hyperacute reaction take place?
Hours
During hyperacute rejection where do the recipient Ab bind on the transplanted organ?
RBC Ag or MHC within the vascular epithelium
What is the test called to see if a patient has antibodies against a given HLA?
Panel Reactive Ab Test
How does a panel reactive Ab test work?
Take the serum from a recipient and put it on leukocytes from different people and therefore people with different HLA
What cells are involved in acute rejection?
T cells
How long does acute rejection take?
Days to weeks
What are the two possible mechanisms for acute rejection?
- Donor cells expressing MHC Class II react with the host immune system (APC within host present)
- Donor cells get expressed by recipient APC
What cells are involved in chronic rejection?
Ab to the transplanted MHC/ minor transplanted Ag- usually Ab to MHC Class I
How long does it take for a chronic rejection to occur?
Months or years
What is alloreactivity?
Reacting to a different individual within the same species
What are the steps in finding a potential transplant match?
Match blood type first, then HLA I and II, find match on computer, cross match on all potential candidates (recipient serum against candidates cells)
What is more important in terms of matching prior to transplantation? HLA I or HLA II?
HLA I
What happens during a mixed lymphocyte reaction?
Take graft lymphocytes and irradiate them so that they can’t proliferate, then add the host lymphocyte and look for any reaction
What testing is done monthly following transplantation in an attempt to avoid rejection?
Screen for anti-HLA Class I
How do corticosteroids work?
Knockout T cells
How do cytotoxic drugs work?
Interfere with DNA synthesis
How do cyclosporin and FK506 work?
Inhibit the signaling used by T cells
What are antilymphocyte globulins? Where do they come from?
Ab directed against T cells- made from animals
With what cancers might you need a BM transplant? Why?
Leukemia/lymphoma; treat with chemo to get rid of the cancer, but knockout the healthy BM at the same time
What happens during GVHD?
Grafts mature T cells attack the host’s cells
What reduces the severity of GVHD?
A better MHC match or removing T cells from the graft
When might a GVHD be helpful?
Appears to be beneficial in engraftment; also might help kill residual tumor in leukemic patients
