<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .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 recipients serum is responsible for this rejection?? A: IgA, B: IgG, C: CD8 T cells, D: CD4 T cells, E: Macrophages,  <response>: This is a question about hyperacute rejection of a transplanted kidney. Hyperacute rejection occurs within minutes to hours after transplantation and is mediated by preformed antibodies in the recipient against donor HLA antigens. This activates complement and leads to endothelial injury and thrombosis in the allograft vasculature. The question stem describes a transplanted kidney that rapidly becomes cyanotic, edematous and dusky with mottling after connection to the recipients circulation. This clinical picture is consistent with hyperacute rejection.Of the answer choices, IgG and IgA antibodies can cause rejection but not hyperacute rejection. CD8 T cells, CD4 T cells and macrophages mediate cellular rejection, which occurs over days to weeks. The only answer choice that could mediate immediate, antibody-mediated rejection is IgG antibodies. Therefore, the correct answer is B.B: IgG 