Memory in adaptive immunity is characterized by the presence of which cells?

• A. Brief, transient antibody-secreting cells
• B. Long-lived B and T cells that respond more rapidly upon re-exposure
• C. Only B cells that have not yet differentiated
• D. Neutrophils with enhanced phagocytic ability

Answer: (B)

Memory in adaptive immunity is defined by long-lived B and T lymphocytes that persist after an initial infection or vaccination and respond much more quickly and robustly upon re-exposure. These memory cells are formed during the first encounter, with B cells becoming memory B cells and T cells becoming memory T cells. When the same antigen appears again, memory B cells rapidly produce antibodies and memory T cells quickly expand to provide help or cytotoxic activity, yielding a faster and stronger secondary response.

Transient antibody-secreting cells are part of the immediate, short-lived plasmablast/plasma cell response and do not persist to confer memory. Naive B cells that have not differentiated have not yet encountered antigen and thus do not provide memory. Neutrophils are innate immune cells; they do not generate the antigen-specific memory characteristic of adaptive immunity.