This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immune system, Subject name: Medicine
[{'content': 'C-ANCA positivity indicates, antibody formed against \nSelect and explain. \nA. Proteinase 3, B. Myeloperoxidase, C. Cytoplasmic antinuclear antibody, D. Anti centromere antibody', 'role': 'user'}, {'content': 'Answer: A \nExplanation: C-ANCAs, or PR3-ANCA, or Cytoplasmic antineutrophil cytoplasmic antibodies, are a type of autoantibody, an antibody produced by the body that acts against one of its own protein . PR3 is the most common antigen target of ANCA in patients with granulomatosis with polyangiitis. Ref - Researchgate.net', 'role': 'assistant'}]