MCAT Biology Question 114: Answer and Explanation
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Question: 114
9. What is the response of the immune system to downregulation of MHC molecules on somatic cells?
- A. B-cells are activated and antibodies are released.
- B. T-cells are activated, resulting in a cytotoxic response.
- C. Natural killer cells induce apoptosis of affected cells.
- D. Macrophages engulf the pathogen and display its antigens.
Correct Answer: C
Explanation:
Healthy cells exhibit MHC class I molecules. Natural killer cells monitor the expression of MHC molecules on the surface of cells. Viral infection and cancer often cause a reduction in the expression of MHC class I molecules on the cell surface. Natural killer cells detect this lack of MHC and induce apoptosis in the affected cells.