This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
[{'content': 'Rheumatoid factor is directed against- \nSelect and explain. \nA. IgG, B. IgD, C. IgM, D. IgA', 'role': 'user'}, {'content': 'Answer: A \nExplanation: harshmohan textbook of pathology *detection of circulating autoantibody called rheumatoid factor against Fc poion of autologous IgG in about 80% of cases', 'role': 'assistant'}]