MCAT Biology Question 117: Answer and Explanation
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Question: 117
12. Upon encountering an antigen, only T-cells with the specific T-cell receptor are activated. This is an example of:
- A. innate immunity.
- B. a cytotoxic T-cell response.
- C. humoral immunity.
- D. clonal selection.
Correct Answer: D
Explanation:
When the adaptive immune system encounters an antigen, only the cells with receptors (antibodies or T-cell receptors) specific to that antigen are activated. This is known as clonal selection. While a T-cell response may be a cytotoxic response, it could also be the activation of helper T-cells; plus, this does not explain the specificity of the response, eliminating choice (B).