What best defines adoptive immunity?

• A. Immunity produced by the host's own immune system
• B. Immunity achieved by transferring immune cells from a donor to the recipient
• C. Immunity present from birth
• D. Immunity gained through pathogens

Answer: (B)

Adoptive immunity is immunity conferred by transferring immune material from another person. Protection comes from donor immune cells or components that are given to the recipient, rather than the recipient’s own immune system having produced the response. For example, transferring donor T cells or hematopoietic stem cells can reconstitute or augment the recipient’s immune defenses. This is a form of passive transfer because the recipient isn’t actively generating the response themselves, at least initially. It differs from immunity that the host develops on its own through infection or vaccination, and from innate immunity present from birth.