Which statement is true about clones of activated lymphocytes?

• A. They are sensitive to the same specific antigen
• B. They respond to multiple different antigens
• C. They do not participate in adaptive immunity
• D. They arise only after vaccination

Answer: (A)

Activated lymphocytes undergo clonal expansion, forming many descendants that all carry the same antigen receptor. Because these cells originate from a single activated lymphocyte, they are all specific for the same antigen. This targeted growth creates a large pool of cells ready to respond to that specific threat, including cells that act as effectors and those that become memory cells. So the clone remains specific to one antigen rather than reacting to many different ones. Clonal expansion happens upon exposure to antigen in infection or vaccination and is a hallmark of adaptive immunity, not something that occurs only after vaccination.