Transplant Immunology Flashcards
What is tolerance
Non-reactivity to a particular antigen
T cell tolerance vs B cell tolerance?
T cell 1 day
B cell 7 days
How long does T cell/B cell tolerance last
T cell up to 6 months
B cell less than 2 months
What is clonal abortion
Exposure of immature B cells to antigen inhibits development of cells with that antigenic specificty
What are the categories of transplant grafts
Autografts - from one organism to the same organism
Allograft - graft from one organism to another in the same species
Xenografts - grafts from different species
What patients are more likely to reject foreign tissue
Women sensitised due to pregnancy
Previous multiple blood transfusion
What HLA types are matched before transplane
A
B
DR locus
How do immune privileged areas differ from other tissues?
Immune communication with the rest of the body is limited - not supplied with lymphatics
High level of anti-inflammatory cytokin TGF-b
Increased expression of FasL - induces apoptosis of infiltrating Fas expressing activated lymphocytes
What are immune privileged areas?
Eyes
Brain
Gonads
Foetus
Placenta
What is acute graft rejection
Cell mediated
7-21 days
Allogenic reaction to donor antigen
What is chornic graft rejection
After 3 months - occurs as a result of disturbing post graft tolerance
What is graft vs host disease?
Graft tissue contains immune cells that recognise host as foreign
Severe inflammatory response - rashes, diarrhoea, liver disease
How to test for GVHD
Lymphocytes from donor mixed with irradiated donors from the host
If potential donor lymphocytes replicate - there are potentially alloreactive responses
Mixed lymphocyte reaction test - important for bone marrow transplant
How are naive alloreactive T cells activated?
Direct allorecognition
- graft dendritic cells present foreign MHC and co-stimulatory molecules to host T cells initiating an alloreactive reaction
Indirect allorecognition
- uptake of foreign antigen by host dendritic cells and presentation to naive alloreactive T cells
(self class I or II MHC molecules)
What is hyperacute rejection
Circulating antibodies are present to antigens on the graft tissue within minutes.
If the receipient is sensitized to donor antigens, graft destruction via cell mediated mechanisms in 2-5 days
