CHT Transplant Immunology 1 — Questions and Answers
Question 1: Which type of rejection occurs within minutes to hours after transplantation and is mediated by preformed donor-specific antibodies?
- Hyperacute rejection (Correct answer)
- Acute cellular rejection
- Chronic rejection
- Accelerated acute rejection
Correct answer: Hyperacute rejection
Hyperacute rejection is caused by preformed donor-specific antibodies that immediately activate complement and cause thrombosis of graft vasculature.
Question 2: Which immune cells are primarily responsible for acute cellular rejection?
- CD4+ and CD8+ T lymphocytes (Correct answer)
- B cells and plasma cells
- NK cells and mast cells
- Neutrophils and eosinophils
Correct answer: CD4+ and CD8+ T lymphocytes
Acute cellular rejection is driven predominantly by host CD4+ and CD8+ T cells that recognize donor alloantigens as foreign.
Question 3: What is the 'indirect pathway' of allorecognition?
- Host T cells recognize donor peptides presented by self HLA on host APCs (Correct answer)
- Host T cells directly recognize intact donor HLA molecules on donor cells
- NK cells recognize missing self HLA on donor cells
- B cells produce antibodies against donor blood group antigens
Correct answer: Host T cells recognize donor peptides presented by self HLA on host APCs
In the indirect pathway, donor HLA proteins are processed into peptides and presented by recipient APCs on self-HLA molecules to recipient T cells.
Question 4: Chronic allograft nephropathy is most closely associated with which long-term immunological mechanism?
- Persistent donor-specific antibody (DSA)-mediated injury (Correct answer)
- Recurrent hyperacute rejection episodes
- Autoimmune anti-tubular basement membrane antibodies
- NK cell cytotoxicity only
Correct answer: Persistent donor-specific antibody (DSA)-mediated injury
Chronic antibody-mediated rejection driven by DSA leads to progressive microvascular injury, transplant glomerulopathy, and eventual graft loss.
Question 5: Which complement pathway is most directly activated by donor-specific antibodies (DSA) bound to graft endothelium?
- Classical complement pathway (Correct answer)
- Alternative complement pathway
- Lectin (MBL) complement pathway
- Terminal pathway only without upstream activation
Correct answer: Classical complement pathway
DSA bound to donor endothelial HLA antigens activate the classical complement pathway via C1q, leading to C4d deposition.
Question 6: What does a positive C4d staining on peritubular capillaries in a kidney biopsy indicate in the transplant setting?
- Antibody-mediated rejection (AMR) (Correct answer)
- Acute cellular rejection only
- Calcineurin inhibitor toxicity
- Viral nephropathy
Correct answer: Antibody-mediated rejection (AMR)
Peritubular capillary C4d deposition is a marker of complement activation by DSA and is a diagnostic criterion for antibody-mediated rejection.
CHT Transplant Immunology 1
Which type of rejection occurs within minutes to hours after transplantation and is mediated by preformed donor-specific antibodies?