This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Rejection of Transplants, Subject name: Pathology
[{'content': 'No prior immune suppression is helpful in which type of graft rejection? \nSelect and explain. \nA. Acuterejection, B. Hyperacute rejection, C. Chronic rejection, D. None of the above', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans is 'b' i.e. Hyperacute rejectiono Hyperacute rejection is caused by ABO incompatibility and preformed cytotoxic antibodies against donor HLA antigens. Therefore immunosuppressant is not helpful.", 'role': 'assistant'}]