MCAT Biology Question 111: Answer and Explanation

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Question: 111

6. Which of the following is an example of adaptive immunity?

  • A. PRRs recognize that a pathogen is an invasive parasite and eosinophils are recruited to the area.
  • B. Complement is activated, causing osmotic instability in a bacterium.
  • C. B-cells generated through vaccination are activated when their antigen is encountered.
  • D. Dendritic cells sample bacteria within a laceration and travel to the lymph nodes to present the antigen.

Correct Answer: C

Explanation:

Adaptive immunity involves the activation of B-cells and T-cells specific to the encountered antigen. Any choice that conforms to this paradigm will be correct. Choice (C) indicates that B-cells are activated. Pattern recognition receptors, or PRRs, in choice (A) recognize patterns common to certain pathogens, but do not identify the specific pathogen. Complement is an example of a blood-borne nonspecific defense against bacteria, eliminating choice (B). Dendritic cells traveling to the lymph nodes in choice (D) are a part of the interaction between the innate and adaptive immune systems, but the dendritic cells themselves are nonspecific.

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