This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Breast, Subject name: Pathology
Which of the following statements about Rheumatoid Factor is true ? 
Select and explain. 
A. It is an IgM antibody directed against IgG, B. It is an IgG antibody directed against 1gM, C. It is more specific than Anti-CCP antibodies, D. It is positive in all cases of Juvenile Rheumatoid Ahritis
A: It is an IgM antibody directed against IgG
Answer: A: It is an IgM antibody directed against IgG 
Explanation: In rheumatoid ahritis it is suspected that antibodies plays a role in the disease. About80% of patients have serun IgM autoantibodies that bind to fc poion of their own self IgG. These antibodies are called rheumatoid factor. Ref :Robbins basic pathology 9th edition page no 784,green box=Pathogenesis