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': 'HLA-I is present on: \nSelect and explain. \nA. All nucleated cells, B. Only on cells of immune system, C. Only on B cells, D. Only on T cells', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., All nucleated cells(Ref: Jawetz, 27th/e, p. 139)* HLA class I Ag - present on the surfaces of all nucleated cells.* HLA class II Ag - only on cells of immune system (macrophages, dendritic cells, activated T cells and B cells).", 'role': 'assistant'}]