Review Question - QID 215154

A 42-year-old woman with a history of orthotopic liver transplant presents to her surgeon with 2 days of fever to 101.0°F (38.3°C) at home and feelings of nausea and fatigue. The patient underwent liver transplantation from a deceased donor 2 months prior, as a result of fulminant liver failure secondary to acetaminophen overdose. She had been recovering well since surgery until these symptoms began. On exam, her temperature is 100.6°F (38.1°C), blood pressure is 108/76 mmHg, pulse is 84/min, and respirations are 14/min. The patient has mild scleral icterus. There is mild abdominal tenderness to palpation, which has been present since surgery. The following labs are drawn:

Hemoglobin: 13.0 g/dL
Leukocyte count: 13,000/mm^3
Aspartate aminotransferase (AST, GOT): 50 U/L (normal: 5-40 U/L)
Alanine aminotransferase (ALT, GPT): 150 U/L (normal: 5-40 U/L)
Alkaline phosphatase (ALP): 280 U/L (normal: 35-130 U/L)

A liver biopsy is performed, showing dense lymphocytic infiltrates. Which of the following is the most likely predominant mechanism for this patient’s rejection?