TID Flashcards
(41 cards)
What was the first transplanted material?
→cornea
What is the difference between autologous and syngeneic donor relationships?
→autologous= within same individual →syngeneic= donor with a genetically identical
What is allogenic transplant?
→Donors and recipients are from the same species but genetically different
What is xenogeneic transplant?
→Donor and recipient are different species
What are immune responses to transplant mainly due to?
→differences the antigens forming the major histocompatibility complex
Where are HLA genes found?
→chromosome 6
What may be foreign in transplants?
→both the MHC protein and the peptide in its binding groove may be foreign
What is the outcome of indirect allorecognition of self HLA and non-self peptide?
→Tcell activation
What is the outcome of direct allo-recognition of non-self HLA in a donor cell?
→Unmatched HLA + peptide = T-cell activation
What needs to be matched to reduce likelihood of problems with transplants?
→match 4/6 MHC class II loci
Compare live and dead donors
→Organs from deceased donors are also likely to be in inflamed condition due to ischemia
→Transplant success is less sensitive to MHC mismatch for live donors
What are the types pf graft rejections?
→Hyperacute rejection
→Acute rejection
→Chronic rejection
When does hyperacute rejection occur?
→Within a few hours of transplant
What type of transplants commonly see hyperacute rejection?
→highly vascularised organs (e.g. kidney)
What is the blood group implicated in hyperacute rejection?
→ABO
→MHC-I
How can antibodies to MHC arise?
→pregnancy
→blood transfusion or previous transplants
How do antibodies cause damage to transplanted tissue?
→Recognition of Fc region leading to -
→Complement activation
→Antibody dependent cellular cytotoxicity -(Fc Receptors on NK cells)
→Phagocytosis- (Fc Receptors on macrophages)
Describe the process of hyperacute rejection
→Antibodies bind to endothelial cells
→complement fixation
→accumulation of innate immune cells
→Endothelial damage, platelets accumulate, thrombi develop
→
What cells are activated in acute rejection?
→organ’s resident dendritic cells
Why is there a Tcell response in acute rejection?
→MHC mismatch
Describe the process of direct allorecognition of foreign MHC
→Inflammation results in activation of organ’s resident dendritic cells
→DC migrate to secondary lymphoid tissue where they encounter circulating effector T cells
→Macrophages and CTL increase inflammation and destroy transplant
What happens in chronic rejection?
alloantibodies recruit inflammatory cells to blood vessel
→Blood vessel walls thickened, lumina narrowed – loss of blood supply
→Correlates with presence of antibodies to MHC-I
What is the main cause of chronic rejection?
→indirect allorecognition of foreign MHC
Describe the process of indirect allorecognition of foreign MHC
→Membrane fragments containing donor MHC are taken up by host DC
→Donor MHC is processed into peptides which are presented by host MHC
→T cell and antibody responses is generated to the peptide derived from processed donor MHC
