This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Medicine
[{'content': 'All of the following immunosuppressives cause profound myelosuppression except: \nSelect and explain. \nA. Sirolimus, B. Cyclosporine, C. Azathioprine, D. Mercaptopurine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ciclosporin&;s main effect is to lower the activity of T-cells; it does so by calcineurin-phosphatase pathway.Unlike cytotoxic immunosuppressants, it is free of toxic effects on bone marrow and RE system as it doesn&;t act on cell cycle.(ref: KD Tripathi 6/e p839)', 'role': 'assistant'}]