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
c-ANCA positivity indicates, antibody formed against: 
Select and explain. 
A. Proteinase 3, B. Myeloperoxidase, C. Cytoplasmic antinuclear antibody, D. Anti centromere antibody
A: Proteinase 3
Answer: A: Proteinase 3 
Explanation: Answer is A (Proteinase 3): Proteinase - 3 (a 29 - kDA serine proteinase) present in neutrophil azurophilic granules is the major c-ANCA antigen. Major c-ANCA antigen Proteinase 3 (PR-3) Major p - ANCA antigen Myeloperoxidase (MPO)