This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
[{'content': 'Which one of the following is called the immunologically sequestered antigen? \nSelect and explain. \nA. Lungs, B. Spleen, C. Thymus, D. Lens of the eye', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ceain self-antigens are present in closed systems and are not accessible to the immune apparatus. These are known as sequestered antigens. An example is the lens antigen of the eye. The lens protein is enclosed in its capsule and does not circulate in the blood.', 'role': 'assistant'}]