A 30-year-old female kidney transplant recipient presents with rising serum creatinine three months post-transplant. A graft biopsy is performed. Which of the following histological findings is most characteristic of acute cellular rejection?

Explanation

Acute cellular rejection (ACR) is primarily mediated by donor-specific T-lymphocytes that recognize donor MHC antigens. It typically occurs within the first few months post-transplant. The hallmark histological feature is a diffuse interstitial lymphocytic infiltrate, often accompanied by tubulitis (lymphocytes infiltrating renal tubules) in kidney transplants, or endotheliitis in other organs. C4d deposition is characteristic of antibody-mediated rejection. Obliterative vasculopathy and intimal fibrosis are features of chronic rejection. Glomerular basement membrane thickening is seen in various glomerular diseases, not typically primary ACR.