MHC and transplanatation Flashcards
In what types of cells is blood group substance found
all vascular endothelial cells.
what 2 types of isoagglutinins do all individuals have
anti A and anti B
what are isoagglutinins
Antibodies produced by an individual that cause agglutination of red blood cells in other individuals.
what happens when a donor is mismatched for the second time
necrosis is much faster.
• This is because the immune system has formed a memory
• 2nd response is more vigorous.
What is MHC
set of genes found in all vertebrate species.
What are the key roles of MHC
immune function- present ‘self’ and ‘nonself’ antigens for inspection by T cell antigen receptors.
disease susceptibility
reproductive success.
what chromosome is MHC found on
6 (short arm)
how many classes of MHC are there
3
which classes of MHC are involved in transplant
class I and class II (encode antigens)
what cell are class I expressed on
all nucleated cells.
What cells are class II antigens expressed on
B lymphocytes and expression can be indued on T lymphocytes
what type of biochemical molecules are MHC/HLA
glycoproteins.
How is MHC inherited
mendelian inheritance
each individual inherits 2 antigens at a given locus.
co-dominant expression. All inherited antigens are displayed on the cell surface.
what type os blood cell has lots of HLA’a
WBC
Is HLA highly polymorphic
Yes large number of allelic variants at each locus.
why is the advantage of having so many types of HLA
survival advantage
– as everyone in the population will have developed resistance and immunity against certain pathogens, overall as a population we have immense immunity to lots of pathogens.
How do we determine different allelic forms of HLA which can form polymorphisms
use primers
Is HLA part of the adaptive or complement immune system
adaptive
What is direct recognition
happens immediately after transplant.
not typical body process.
T cells get through due to damage of capillary wall from surgery and stress and bind to graft.
What is indirect recognition
normal process.
APC moves into tissue and is presented with graft peptides which it then processes and presents
migrates to lymph nodes where it can present it to T cells, which migrate to the graft
What is semidirection recognition.
- Recipient APc move in to tissue
- Binds with donor APC
- Migration of this new APC to lymph nodes where it will present to T cells.
define sensitization
Any event which elicits an HLA directed immune response
• Pregnancy- foetus is allograft
• Blood transfusion- contain WBC which have HLA.
• Transplantation- HLA or the donor
what methods are used to prevent sensitisation
- Serum screening- determines patients and donors HLA profile to see if they match
- Cross matching- checks recipients’ serum against donors.
How does cross matching take place
- Donor T lymphocyte with HLA
- Recipient serum added which many contain antibodies against the HLA.
- Florescence second antibody is used to see whether the antibody- HLA complex has formed
- This is read through a detector.
when does a hyper acute rejection occur
severely mismatched HLA
What happens in hyper acute rejection
• Antibodies in the recipient bind to endothelial cells of the transplant as they class it as foreign • This activates the coagulation cascade – Activate clotting cascade – Activate complement – Transplant becomes leaky and necrotic
