Which of the following best describes memory B cells in the immune response?

• A. Thymocytes
• B. Memory B cells
• C. Monocytes
• D. Neutrophils

Answer: (B)

Memory B cells are long-lived B lymphocytes formed after an initial exposure to an antigen. They persist in lymphoid tissues and the bloodstream, ready to respond quickly if the same antigen is encountered again. When re-exposure occurs, these cells rapidly proliferate and differentiate into plasma cells that produce large quantities of high-affinity antibodies, producing a faster and stronger secondary immune response. This quick recall and reinforced antibody production is what characterizes the memory B cell response.

They are not thymocytes (T cell precursors), monocytes (which become macrophages and dendritic cells), or neutrophils (a type of innate immune cell), which is why memory B cells uniquely describe this aspect of humoral immunity.