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: Pathology
[{'content': 'A 40-year-old man has a chronic cough with fever for several months. The chest radiograph reveals a diffuse reticulonodular pattern. Microscopically on transbronchial biopsy, there are focal areas of inflammation containing epithelioid cell granuloma, Langhans giant cells, and lymphocytes. These findings are typical for which of the following type of hypersensitivity immunologic responses: \nSelect and explain. \nA. Type IV, B. Type II, C. Type III, D. Type I', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Presence of epithelioid cell granuloma, Langhans giant cells and lymphocytes is characteristic of chronic\xa0granulomatous inflammation\nChronic granulomatous inflammation occurs when two conditions are satisfied i.e.\n\na. When an active T lymphocyte-mediated cellular immune response occurs.\n\nLymphokines produced by activated T lymphocytes inhibit migration of macrophages and cause them to\xa0aggregate in the area of injury and form granulomas.\nThis pathological process is characteristic of Type IV hypersensitivity (so one can say that- Type IV\xa0hypersensitivity is essential for chronic granulomatous inflammation)\n\nb. When macrophages have successfully phagocytosed the injurious agent but it survives inside them.\n\nSome important definitions- • Epithelioid cells - These are activated macrophages\nThey are large cells with abundant pale foamy cytoplasm\nEpithelioid cell granuloma\nAn epitheloid cell granuloma is an aggregate of these activated macrophages.\nGranulomas are usually surrounded by lymphocytes, plasma cells fibroblast and collagen.\nLanghans giant cells\nIt is a typical feature of epithelioid cell granuloma. These are formed by the fusion of macrophages and characterized\xa0by 10-50 nuclei around the periphery.', 'role': 'assistant'}]