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': 'Relative to the primary immunological response, secondary and later booster responses to a given hapten-protein complex can be associated with which one of the following? \nSelect and explain. \nA. Lower titers of antibody, B. Increased antibody affinity for the hapten, C. Decreased antibody avidity for the original hapten-protein complex, D. Maintenance of the same subclass, or idiotype, of antibody produced', 'role': 'user'}, {'content': 'Answer: B \nExplanation: With repeated immunization, higher titers of all antibodies are observed, and, as priming is repeated, the immune response recruits B cells of progressively greater affinity. The affinity of antibody for a hapten-protein complex rises, cross-reactivity also rises, and the response becomes wider in specificity. As the number of antigenic sites detected per reacting particle increases, the avidity increases. In addition to shifts in the class of immunoglobulin synthesized in response to an antigen (IgM to IgG), shifts also may occur in the idiotype of antibody.', 'role': 'assistant'}]