Post-renal transplant, a recipient develops acute rejection on day 5. Biopsy shows dense CD8+ T-cell infiltrate and tubulitis. HLA crossmatch was negative pre-transplant. What is the most likely mechanism?

• A Antibody-mediated rejection via preformed donor-specific antibodies
• B Direct allorecognition by recipient CD8+ T cells of donor HLA-I ✓
• C Hyperacute rejection due to ABO mismatch
• D Indirect allorecognition via processed peptides on recipient APCs

Explanation

Acute cellular rejection occurring within days is primarily driven by direct allorecognition — recipient CD8+ T cells recognise intact foreign HLA class I molecules on donor tubular epithelial cells and destroy them, producing the characteristic tubulitis. Antibody-mediated rejection (ABMR) shows peritubular capillary C4d deposition and neutrophil margination. Hyperacute rejection occurs within minutes and requires preformed ABO or anti-HLA antibodies. Indirect allorecognition typically drives chronic rejection.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.