This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'No prior immune suppression is helpful in which type of graft rejection ? \nSelect and explain. \nA. Acute rejection, B. Hyperacute rejection, C. Chronic rejection, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Answer- B. Hyperacute rejectionHyperacute rejection is caused by ABO incompatibility and preformed cytotoxic antibodies against donor HLA antigens.', 'role': 'assistant'}]