A renal transplant recipient on tacrolimus + mycophenolate mofetil develops acute rejection at 10 days post-transplant. Renal biopsy shows diffuse interstitial infiltrate of CD4+ and CD8+ lymphocytes with tubulitis. What type of hypersensitivity reaction is this?
- A Type II (cytotoxic) hypersensitivity mediated by preformed anti-HLA antibodies
- B Type III (immune complex) mediated hypersensitivity with complement deposition
- C Type I (IgE-mediated) anaphylactic hypersensitivity
- D Type IV (delayed-type / cell-mediated) hypersensitivity involving donor-antigen-specific T-cell activation ✓
Explanation
Acute cellular rejection occurs within days to weeks of transplantation and is mediated by Type IV (cell-mediated) hypersensitivity: recipient T cells (CD4+ helper and CD8+ cytotoxic) recognize donor MHC antigens (direct allorecognition) or processed donor peptides (indirect), leading to T-cell proliferation and inflammatory destruction of the graft. The histological hallmark is an interstitial mononuclear infiltrate with tubulitis. Antibody-mediated rejection (AMR) involves Type II (preformed anti-HLA antibodies) and shows microvascular injury, C4d deposition, and peritubular capillaritis.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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