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': 'which antibody is called the millionaire molecule \nSelect and explain. \nA. IgA, B. IgM, C. IgG, D. IgD', 'role': 'user'}, {'content': "Answer: B \nExplanation: IgM: Immunoglobulin M (IgM), the largest pentameric immunoglobulin is used as a marker of recent primary infection for some diseases. IgM constitutes 5-10% of serum immunoglobulins in adults. IgM has a half life of 5 days. Because of its high molecular weight (900,000- 1000,000), it is often called macroglobulin and the 'millionaire molecule Ref : Ananthanarayana textbook of Microbiology 9th edition Pgno : 98", 'role': 'assistant'}]