Natural killer cells provide ______ immunity.

• A. innate
• B. humoral
• C. adaptive
• D. passive

Answer: (A)

Verified step by step guidance

1. Understand the types of immunity: Immunity can be broadly categorized into innate immunity and adaptive immunity. Innate immunity is the body's first line of defense and is non-specific, while adaptive immunity is specific and involves memory cells.
2. Define natural killer (NK) cells: NK cells are a type of lymphocyte that play a crucial role in the immune system by targeting and destroying virus-infected cells and tumor cells without prior sensitization.
3. Determine the type of immunity NK cells belong to: Since NK cells act quickly and non-specifically without requiring prior exposure to a pathogen, they are part of the innate immune system.
4. Eliminate incorrect options: Humoral immunity involves antibodies produced by B cells (adaptive immunity), adaptive immunity involves specific responses and memory, and passive immunity involves the transfer of antibodies from another source (e.g., maternal antibodies).
5. Conclude the correct answer: Based on the characteristics of NK cells, they provide innate immunity.