Question: A 37 year old male with end-stage renal disease undergoes a renal allograft. Within minutes of restoring recipient blood flow to the donor kidney it becomes pale and flabby and rapidly turns purple. The allograft does not function. The pathogenesis of this rejection is most likely which of the following? Stimulation of recipient T-cells by presentation of donor subcellular material by recipient dendritic cells Pre- existing complement fixing antibodies directed against graft antigens Memory B- cells reactive for an allogeneic HLA type present on the kidney Naïve B -cells reactive to an allogeneic HLA type present on the kidney Stimulation of recipient T- cells by direct interaction with their receptors expressed on donor dendritic cells