Which of these is an example of an innate immune defense?

• A. Clonal selection of lymphocytes
• B. Skin acting as a physical barrier
• C. Memory T cell activation
• D. Production of antibodies by B cells

Answer: (B)

Verified step by step guidance

1. Understand the difference between innate and adaptive immunity. Innate immunity is the body's first line of defense and responds quickly and non-specifically to pathogens, while adaptive immunity is specific and involves memory cells.
2. Identify the options related to adaptive immunity: 'Clonal selection of lymphocytes', 'Memory T cell activation', and 'Production of antibodies by B cells' are all part of the adaptive immune response because they involve specific recognition and memory.
3. Recognize that 'Skin acting as a physical barrier' is a non-specific defense mechanism that prevents pathogens from entering the body, which is characteristic of innate immunity.
4. Recall that innate immune defenses include physical barriers (like skin and mucous membranes), chemical barriers, and cellular defenses such as phagocytes.
5. Conclude that the example of an innate immune defense among the options is the skin acting as a physical barrier.