In relation to immunity, how do innate and adaptive systems differ in memory?

• A. Innate immunity has memory; adaptive has none.
• B. Innate memory exists; adaptive memory is absent.
• C. Innate immunity has no memory; adaptive immunity has memory that improves responses on re-exposure.
• D. Both have memory that behaves identically.

Answer: (C)

Memory in immunity means the system improves its response after a prior encounter with the same pathogen. Innate immunity acts quickly and non-specifically, using barriers, phagocytes, and inflammatory signals, but it does not form lasting, pathogen-specific memory. Adaptive immunity, on the other hand, builds memory through B and T lymphocytes. After the first exposure, some B cells become memory B cells and some T cells become memory T cells. When the same pathogen is encountered again, these memory cells respond rapidly and more robustly, producing antibodies and targeted T cell responses that are quicker and stronger than the initial encounter.

So the best statement is that innate immunity has no memory, while adaptive immunity has memory that improves responses on re-exposure. (There is discussion of trained immunity in innate cells in modern research, but the classic distinction emphasizes memory as a feature of adaptive immunity.)