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: Microbiology
[{'content': 'The development of cells of immune system in the individual is called as: \nSelect and explain. \nA. Ontogeny, B. Phylogeny, C. Allogeny, D. Heterogeny', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Immunological ontogeny:\nThe origin and development (=ontogeny) of the lymphocyte system, from its earliest stages to the two major populations of mature lymphocytes: the thymus dependent or T lymphocytes, and the thymus-independent or B lymphocytes.', 'role': 'assistant'}]