Question

In gene therapy of Adenosine Deaminase (ADA) deficiency, the patient requires periodic infusion of genetically engineered lymphocytes because:

• A. Retroviral vector is introduced into these lymphocytes
• B. Gene isolated from marrow cells producing ADA is introduced into cells at embryonic stages
• C. Lymphocytes from patient’s blood are grown in culture, outside the body
• D. Genetically engineered lymphocytes are not immortal cells.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Gene therapy aims to correct genetic defects. For ADA deficiency, functional genes are introduced into the patient's cells.
Detailed Explanation:
1. Lymphocytes are extracted from the patient and cultured.
2. A functional ADA cDNA is introduced into these lymphocytes.
3. These cells are returned to the patient.
4. Since lymphocytes have a limited lifespan (they are not immortal), they eventually die and are replaced by the patient's own defective cells. Thus, the patient needs periodic infusions.
A permanent cure is possible only if the functional gene is introduced into marrow cells at the embryonic stage.
Step 2: Final Answer:
The lack of immortality of the lymphocytes necessitates periodic treatment.