Transplant immunology Flashcards
What provides your personal immune system and defines ‘self’?
MHC
Which cells express MHC2?
antigen-presenting cells
Which cells express MHC1?
most cells - except neurons and RBCs
What do T cells ignore?
MHC+ self peptide
When are T-cells recognising MHC+ self peptide eliminated?
during thymic selection
Where do T cells differentiate?
thymus
What is VDJ recombination?
process by which T cells and B cells randomly assemble different gene segments in order to generate unique antigen receptors
provides T cell diversity
Where does VDJ recombination occur?
in the thymus before T cells get to the lymph nodes
self reactive T cells are removed in the thymus before they get to lymph nodes
How does the thymus educate T cells?
epithelium of thymic medulla educates T cells by presenting self proteins (peptides) to immature T cells
immature T cells that have strong binding for MHC self peptide die
elimination of self reactive T cells = central tolerance or negative selection
Name some types of organ transplant rejection
hyperacute rejection - minutes to hours
acute rejection - weeks to months
chronic rejection - months to years
What happens in an acute allograft rejection?
MHC is not identical
tissue is seen as non-self and stimulates the formation of helper T cells that recognise the transplants MHC proteins
What is graft vs host disease?
activated T cells from the donor enter the host and cause damage to epithelial cells of skin, liver and gut
most important for haematopoietic transplants: bone transplants where lots of donor T cells are delivered into patient
What is the action of immunosuppressive drugs post-transplant?
slow the activation of T cells
(cyclosporin, tacrolimus, sirolimus)
What is the action of steroids post-transplant?
reduce pro-inflammatory cytokine production
