This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Macroglobulin is derived from \nSelect and explain. \nA. B cells, B. T cells, C. Both, D. NK cells', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ref Robbins 9/e p191 alpha-2-Macroglobulin (a2M) is a large (720 KDa) plasma protein found in the blood. It is mainly produced by the liver, and also locally synthesized by macrophages, fibroblasts, and adrenocoical cells. In humans it is encoded by the A2M gene', 'role': 'assistant'}]