In adaptive immunity, which cells differentiate into antibody-secreting plasma cells?

• A. B lymphocytes
• B. T lymphocytes
• C. Natural killer cells
• D. Macrophages

Answer: (A)

In adaptive immunity, B cells differentiate into antibody-secreting plasma cells. When a B cell encounters its specific antigen and receives help from helper T cells, it activates and proliferates, then becomes a plasma cell that churns out antibodies. These antibodies circulate to neutralize pathogens and tag them for attack by other immune cells. The other cell types have different roles: T lymphocytes drive cellular immunity, natural killer cells participate in early, innate defense, and macrophages are phagocytes that digest microbes and present antigens. Thus, B lymphocytes are the ones that become antibody-secreting plasma cells.