A renal transplant patient develops acute rejection 10 days post-transplant with rising creatinine, fever and graft tenderness. Biopsy shows lymphocytic infiltration of the tubules and interstitium. What is the primary immunological mechanism?

• A Pre-formed anti-donor antibodies activating complement
• B NK cell-mediated missing-self recognition
• C Regulatory T-cell depletion causing graft-versus-host disease
• D CD8+ cytotoxic T-lymphocytes recognising donor HLA via direct allorecognition ✓

Explanation

Acute cellular rejection (typically days to weeks post-transplant) is primarily mediated by CD4+ and CD8+ T lymphocytes that recognise intact donor MHC molecules on graft dendritic cells (direct pathway). Biopsy showing interstitial lymphocytic infiltrate is the hallmark. Hyperacute rejection (minutes to hours) is caused by pre-formed antibodies. NK cell missing-self killing contributes but is not the primary mechanism in classic acute rejection. GvHD is seen in bone marrow, not solid organ transplants.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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