Repeated transfusions of genetically modified cells are required in SCID patients and in enzyme replacement theraphy because

Options

A. Transfused cells have a limited life span
B. Introduced gene has been mutated
C. The enzyme required is degraded after 20 days of transfusion
D. Both (1) & (3)

Answer

**Step-by-Step Solution:**

1. **Understanding SCID**: SCID stands for Severe Combined Immunodeficiency. It is a genetic disorder characterized by the absence of functional T and B lymphocytes, leading to a severely compromised immune system.

2. **Cause of SCID**: One of the main causes of SCID is the deficiency of the enzyme adenosine deaminase (ADA). This enzyme is crucial for the proper functioning of the immune system.

3. **Treatment Options**: The treatment for SCID can involve enzyme replacement therapy, where the missing enzyme (ADA) is provided to the patient. This can be done through transfusions of genetically modified cells that produce the enzyme.

4. **Limitations of Transfusions**: The transfused genetically modified cells have a limited lifespan. This means that after a certain period, these cells will die off, and the patient will need repeated transfusions to maintain the necessary enzyme levels.

5. **Degradation of Enzymes**: Additionally, the enzymes provided through these transfusions may also degrade after a certain time (approximately 20 days). This necessitates the need for ongoing treatment to ensure that the patient continues to receive the required enzymes.

6. **Conclusion**: Therefore, repeated transfusions of genetically modified cells are required in SCID patients and in enzyme replacement therapy because:
- The transfused cells have a limited lifespan.
- The enzymes they produce degrade after a certain period.

Thus, the correct answer is that both statements regarding the limited lifespan of transfused cells and the degradation of the enzyme after 20 days are true.

**Final Answer**: Both 1 and 3 are correct.

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