Hyperacute, acute, and chronic transplant rejection mechanisms and graft-versus-host disease tested on USMLE Step 1.
30 cards · basic cards · AI-written, checked twice. Edit anything.
- What causes hyperacute transplant rejection?
- Preformed recipient antibodies against donor antigens (e.g., ABO or HLA).
- How soon after transplantation does hyperacute rejection occur?
- Within minutes to hours.
- What is the primary target of antibody attack in hyperacute rejection?
- Vascular endothelium of the graft.
- What is the characteristic histologic finding in hyperacute rejection?
- Widespread microvascular thrombosis with graft necrosis.
- What test is performed before transplant to prevent hyperacute rejection?
- Crossmatch test (recipient serum mixed with donor lymphocytes).
- What type of hypersensitivity reaction is hyperacute rejection?
- Type II hypersensitivity.
- How soon after transplantation does acute rejection typically occur?
- Weeks to months.
- What is the main cellular mechanism of acute cellular rejection?
- Recipient cytotoxic T cells attack donor graft cells.
- What is the characteristic histologic finding in acute cellular rejection?
- Dense mononuclear (lymphocytic) infiltrate in the graft.
- What causes acute humoral (antibody-mediated) rejection?
- Newly formed (de novo) antibodies against donor endothelial antigens.
- Is acute transplant rejection typically reversible?
- Yes, often with increased immunosuppressive therapy.
- What type of hypersensitivity reaction is acute cellular rejection?
- Type IV (delayed-type) hypersensitivity.
- How long after transplantation does chronic rejection typically develop?
- Months to years.
- What is the dominant histologic feature of chronic transplant rejection?
- Vascular fibrosis and graft arteriosclerosis (intimal thickening).
- Is chronic transplant rejection reversible with immunosuppression?
- No, it is largely irreversible.