This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'C- ANCA positivity indicates, antibody formed against which of the following? \nSelect and explain. \nA. Proteinase 3, B. Myeloperoxidase, C. Cytoplasmic antinuclear Antibody, D. Anti centromere Antibody', 'role': 'user'}, {'content': "Answer: A \nExplanation: C-ANCAs (Cytoplasmic anti-neutrophil cytoplasmic antibodies), are a type of autoantibody formed against proteinase 3. P-ANCA (Perinuclearanti-neutrophil cytoplasmic antibodies) are antibodies directed against myeloperoxidase. Ref: Harrison's Principles of Internal Medicine, 16th Edition, Page 2002; Thurlbeck's Pathology Of The Lung, William M. Thurlbeck, 3rd Edition, Page 372; Rheumatology Secrets, Sterling G. West, 2nd Edition, Page 226.", 'role': 'assistant'}]