Which of the following is a unique characteristic of adaptive immunity?

• A. Ability to fight infection
• B. Ability to remember a prior exposure to a pathogen
• C. A similar response to all pathogens encountered
• D. Process of phagocytosis to destroy a pathogen

Answer: (B)

The distinctive feature of adaptive immunity is immunological memory—the ability to remember a previous encounter with a pathogen and respond more quickly and effectively upon re-exposure. This happens when B and T lymphocytes that recognize a specific pathogen are selected and expand, forming long-lived memory cells. Later exposures trigger a faster, stronger, and more targeted response, often neutralizing the pathogen before it causes illness.

Phagocytosis and broad infection-fighting are typical of innate immunity, which is non-specific and does not create lasting, pathogen-specific memory. The idea of a uniform response to all pathogens also doesn’t fit adaptive immunity, which is highly specific to particular antigens. So, the unique characteristic here is the ability to remember prior exposure.