Which of the following is NOT a characteristic of natural killer (NK) cells?

• A. They play a role in the innate immune response.
• B. They can induce apoptosis in target cells.
• C. They require prior exposure to antigens to function.
• D. They can recognize and kill virus-infected cells.

Answer: (C)

Verified step by step guidance

1. Understand the role of natural killer (NK) cells in the immune system. NK cells are a type of lymphocyte that play a crucial role in the body's innate immune response.
2. Recognize that NK cells have the ability to induce apoptosis, which is a process of programmed cell death, in target cells such as virus-infected cells or tumor cells.
3. Identify that NK cells can recognize and kill virus-infected cells without the need for prior sensitization to specific antigens.
4. Differentiate between innate and adaptive immune responses. NK cells are part of the innate immune system, which provides a rapid response to a wide range of pathogens without prior exposure.
5. Conclude that the statement 'They require prior exposure to antigens to function' is NOT a characteristic of NK cells, as this is a feature of the adaptive immune system, not the innate immune system where NK cells operate.