In the process of gene therapy for ADA deficiency, lymphocytes are periodically infused into the patient. Which of the following statements correctly justifies this requirement?
- AThe retroviral vector used is unstable and degrades rapidly in the patient's body.
- BThe genetically engineered lymphocytes have a limited lifespan and are not immortal.
- CThe recipient's immune system recognizes and destroys the modified lymphocytes.
- DThe introduced ADA gene undergoes silencing over time, rendering the lymphocytes ineffective.
✓ Correct answer: B
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