This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hypersensitivity, Subject name: Pathology
[{'content': 'Toluidine blue staining is used for identification of? \nSelect and explain. \nA. Mast cell, B. Fibroblast, C. Melanocyte, D. Macrophages', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Mast cell Located in blood vessel and sub epithelial tissues Mast cells contain granules which contain proteoglycans. Granules stain positive with metachromatic stains such as:- Giemsa Toluidine blue', 'role': 'assistant'}]