question: Q:A 10-year-old boy is presented to the hospital for a kidney transplant. In the operating room, the surgeon connects an allograft kidney renal artery to the aorta, and after a few moments, the kidney becomes cyanotic, edematous, and dusky with mottling. Which of the following in the recipient’s serum is responsible for this rejection?? 
  {'A': 'IgA', 'B': 'IgG', 'C': 'CD8+ T cells', 'D': 'CD4+ T cells', 'E': 'Macrophages'},