1. A 32-year-old, blood type A positive male receives a kidney transplant from a blood type B positive female donor with whom he had a 6-antigen HLA match. Once the kidney is anastomosed to the man's vasculature, the transplant team immediately begins to observe swelling and interstitial hemorrhage. After the surgery, the patient developed fever and leukocytosis and produced no urine. Which of the following is the most likely explanation?