MCAT Biology Question 115: Answer and Explanation
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Question: 115
10. Which of the following correctly indicates the response of CD8+ T-cells when activated?
- A. Secretion of cytotoxic chemicals
- B. Causing isotype switching
- C. Presentation of antigens
- D. Activation of B-cells
Correct Answer: A
Explanation:
CD8+ T-cells are largely responsible for the cytotoxic immune response. By releasing toxic chemicals into virally infected cells, CD8+ T-cells are able to kill these cells in an effort to contain viral infections. Isotype switching refers to changes in the isotype of antibody produced, which is not caused by CD8+ cells, eliminating choice (B). Antigens are presented by macrophages, dendritic cells, certain epithelial cells, and some B-cells, eliminating choice (C). B-cells are not activated by cytotoxic T-lymphocytes, eliminating choice (D).