Which statement best describes a typical secondary (anamnestic) immune response?

• A. It takes longer to reach the log phase.
• B. The serum titer rises to a higher level than during the primary response.
• C. The response is briefer than the primary response.
• D. The antibody levels are less protective than in the primary response.

Answer: (B)

Secondary immune responses rely on memory B cells and plasma cells formed during the first encounter. When the same antigen shows up again, these memory cells respond rapidly and mount a much stronger antibody production, so the antibody level in the blood rises to a higher peak than after the initial exposure. This quicker, more vigorous response reflects affinity maturation and efficient isotype switching that occurred during the primary response, resulting in antibodies that are more effective at neutralizing the antigen.

That’s why the statement about a higher serum antibody level after re-exposure best fits. The other ideas don’t match how memory responses behave: secondary responses are not slower or longer to develop, and they are not less protective; instead, they tend to be quicker, peak higher, and often generate antibodies with better functional quality.