This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
[{'content': 'A 47-year-old male has a history of end stage renal failure and required a kidney transplant. Approximately four weeks after receiving his transplanted kidney he developed oliguria, fever, hypertension and pain or tenderness over his allograft. On the basis of the findings, the most likely underlying immunological process is: \nSelect and explain. \nA. Autoimmunity, B. Acute rejection, C. Chronic rejection, D. Hyperacute rejection', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b)The time span is appropriate for acute rejection of the transplanted organ but not for chronic or hyperacute rejection. There is no information suggesting autoimmunity. Peripheral tolerance is a mechanism for preventing responses to self antigen.', 'role': 'assistant'}]