11: Transplantation Flashcards
3 mechanisms of immunological privilege
- extracellular fluid in area doesn’t leave via lymphatic system
- TGFbeta [inhibitory cytokine] is produced at these sites
- Fas ligand reacts with Fas on lymphocytes to induce apoptosis
3 types of rejection
hyperacute
acute
chronic
Most important mechanism for allographic t-helper cell activation
alloreactivity
alloreactivity
donor APC presents foreign MHC and self peptide but the recipient T cell is fooled and thinks it sees the exact opposite and is therefore activated
mechanism of alloreactivity once antigen is presented
- CD4 T cells are activated by antigen
- CD4 T cells provide IL2 and IFNgamma to activate CD8 cells
- CD8 cells produce CTLs that lyse grat cells, B cells produce anti-graft antibodies
corticosteroids in immunosuppression
- lyse immature t cells
- block release of cytokines from macros and inhibit leukocyte migration
cyclosporine in immunosuppression
- prevents cell-mediated immunity (Tcells) by inhibiting IL2 and IFNgamma expression
- best at stopping primary immune response
- keeps memory response
- can be nephrotoxic
anti-lymphocyte globulin
- kills wanted and unwanted lymphocytes
- can reverse acute graft rejection
- serum sickness is a side effect
Prevent GVHD
Anti-CD3 antibodies with complement (used in signal transduction in T cells)
Graft-versus-leukemia effect
prevents recurrence of cancer because GVHD removes residual cancer cells
autologous peripheral blood stem cell transplantation
less invasive and less chance of minimal residual disease form of bone marrow transplantation
G-CSF is used to mobilize bone marrow stem cells to blood
What 3 mechanisms protect the fetal allograph?
- trophoblasts don’t express dad MHC [HLA-G stops NKcells attacking the cells without MHC]
- trophoblast secrete inhibitory cytokines such as TGFbeta
- break down trypotphan needed for t-lymphocytes with the enzyme indolamin2,3dioxygenase [trp needed for lymphocytes to react to antigen]
