transplant immunology Flashcards
what is variable DJ recombination
the process by which T cells and B cells randomly assemble different gene segements in order to generate unique antigen receptors -> production of binding sites specific to any possible antigen
what are the 2 stages of high activity of the thymus
- birth
- puberty
shrinks after this as majority person has been exposed to majority of different antigens by then
what will double positive cells (CD4+/CD8+) that interact w MHC II eventually become
CD4+ (t helper)
what will double positive cells (CD4+/CD8+) that interact w MHC I eventually become
CD8+ (cytotoxic)
in a transplanted organ, what is detected by the immune system to cause a reaction
the MHC of the transplamted tissues are presented as “non-self” and so the immune system thinks that it is infected tissue
why do close relative donors increase the chance of transplant survival
closer match of HLA/MHC => less chance of it being recognised as non-self
what is needed for the B cells to make antibodies (2)
- binding of T helper cell
- MCH II (binding to T helper)
other than HLA, what must be a match for transplant
compatible ABO blood group
why are blood transfusions rejected if they are not cross matched
while RBCs don’t express MHC, they express different sugar groups on the cell membranes (A,B, H etc.) -> if the wrong one is expressed it is recognised as non-self
types of organ transplant rejection
allo-graft rejections:
1. hyper acute (minutes to hours)
2. acute reaction (weeks to months)
3. chronic rejection (months to years)
what happens in a hyper acute transplant rejection
ABO blood group mismatch -> antibodies bind blood group antigen on tissue
what type of hypersensitivity reaction is hyper acute rejection
antibody mediated -> type II
what occurs in an acute allograft rejection
MHC on the transplant is not identical, tissue is seen as non-self and stimulates to formation of T helper cells against the transplant
what are the 2 types of allograft rejection
- direct: dendritic cells exit from the tissue graft and express non self MHC and non self peptide, short lived -> acute rejection
- indirect: self MHC enter the graft and digest dead cells resulting in the expression of graft antigens in MHC complexes, longer lived reaction -> chronic rejection
what is graft vs host disease and what type hypersensitivity reaction is it
he graft’s immune cells recognize the host as foreign and attack the recipient’s body cells
-> cell mediated T4 hypersensitivity
