Transplant Rejection

Question 1

Acute

Answer 1

Onset: weeks to months
Pathogenesis: Cellular-CD8 Tcells activated against donor MHC. Humoral: similar to hyperacute except abs develop after transplant.
Features: Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate. Prevent/reverse with immunosuppressents

Question 2

Chronic

Answer 2

Onset: months to years
Pathogenesis: CD4 T cells respond to recipient APCs presenting donor peptides including allegeneic MHC. Both celluar and humoral components
Features: Recipient T cells react and secrete cytokines –> proliferation of vascular smooth muscle and parenchymal fibrosis. Dominated by arteriosclerosis.

Question 3

Graft vs Host

Answer 3

Onset: varies
Pathogenesis: Grafted immunocompetent T cells proliferate in the immunocompromised host and reject host cells with foreign proteins –> severe organ dysfunction.
Features: maculopapular rash, jaundice (hemolysis), diarrhea, hepatosplenomegaly. Usually in bone marrow and liver transplants (rich in lymphocytes). Potentially beneficial in bone marrow transplant for leukemia (graft vs host effect).

Question 4

Hyperactue

Answer 4

Onset: Within minutes (immediate)
Pathogenesis: Pre-existing recipient abs react to donor antigen (type II hypersensitivity rxn), activate complement
Features: Widespread thrombosis of graft vessels –>ischemia/necrosis, graft must be removed