Transplant rejection Flashcards
Which type of transplant rejection takes place within minutes?
Hyperacute
What is pathogenesis of hyperacute transplant rejection?
Pre-existing recipient antibodies react to donor antigen (type II hypersensitivity reaction), activate complement
Widespread thrombosis of graft vessels leading to ischemia, occlusion and fibrinoid necrosis is a feature of which type of transplant rejection?
Hyperacute
Features of hyperacute transplant rejection?
Rx
- Widespread thrombosis of graft vessels leading to ischemia, occlusion and fibrinoid necrosis
- caused by ABO blood type incompatibility (rare)
- Presents while still in surgery > thrombosis occlusion of graft vessels
Rx
Graft must be removed
What is the onset of acute transplant rejection?
Weeks to months
Which type of transplant rejection takes place within weeks to months?
Acute transplant rejection
What is difference of onset (timing) of acute & hyperacute transplant rejection?
Hyperacute : within minutes
Acute: weeks to months
What is pathogenesis of acute transplant rejection?
Cellular: CD8+ T cells and/or CD4+ T cells activated against donor (foreign) MHCs
>(type IV hypersensitivity reaction)
Humoral: similar to hyperacute, except antibodies develop after transplant
>(associated with C4d deposition)
Features of acute transplant rejection?
Rx
- Inflammation (vasculitis) of graft vessels with dense interstitial lymphocytic infiltration
- most common type of transplant rejection
Prevent/reverse with immunosuppressants
What is the onset of chronic transplant rejection?
Months to years
What is pathogenesis of chronic transplant rejection?
CD4+ T cells respond to recipient APCs presenting donor peptides, including allogeneic MHC
Both cellular and humoral components
>(type II and IV hypersensitivity reactions)
Features of chronic transplant rejection?
Examples
- Recipient T cells react to donor MHC (‘looking like’ self MHC carrying antigen) and secrete cytokines
→ proliferation of vascular smooth muscle (intimal thickening)
→ interstitial fibrosis of graft vessels
→ parenchymal graft atrophy - Dominated by arteriosclerosis
Organ-specific examples:
- Chronic allograft nephropathy
- Bronchiolitis obliterans
- Accelerated atherosclerosis (heart)
- Vanishing bile duct syndrome
What is pathogenesis of Graft-versus-host disease?
Grafted immunocompetent T cells proliferate in the
immunocompromised host and reject host cells with “foreign” proteins → severe organ dysfunction
> Type IV hypersensitivity reaction
Features of Graft-versus-host disease?
Rx
Maculopapular rash
Jaundice
Diarrhea
Hepatosplenomegaly
Most commonly seen in bone marrow transplants and liver transplants (rich in lymphocytes)
Rx
For patients who are immunocompromised, irradiate blood products prior to transfusion to prevent GVHD
Why can graft-versus-host disease be potentially beneficial in patients with leukemia?
Potentially beneficial in bone marrow transplant for leukemia
‘Graft-versus tumor effect’
The graft contains donor T cells (T lymphocytes) that can be beneficial for the recipient by eliminating residual malignant cells
