MCAT Biology Question 110: Answer and Explanation

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Question: 110

5. Which of the following is NOT an example of a nonspecific defense mechanism?

  • A. Skin provides a physical barrier against invasion.
  • B. Macrophages engulf and destroy foreign particles.
  • C. An inflammatory response is initiated in response to physical damage.
  • D. Cytotoxic T-cells destroy cells displaying foreign antigens.

Correct Answer: D

Explanation:

The body employs a number of nonspecific defense mechanisms against foreign invasion. The skin and mucous membranes provide a physical barrier against bacterial invasion. In addition, sweat contains enzymes that attack bacterial cell walls. Certain passages, such as the respiratory tract, are lined with ciliated mucus-coated epithelia, which filter and trap foreign particles. Macrophages engulf and destroy foreign particles. The inflammatory response is initiated in response to physical damage. The only choice that is not a nonspecific defense mechanism is choice (D), the correct answer. Cytotoxic T-cells are involved in (specific) cell-mediated immunity.

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