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

Question

Question

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

Answer 1

Concept:

Adenosine Deaminase (ADA) is an enzyme required for the proper functioning of the immune system.
ADA deficiency is caused due to deletion of the gene for the enzyme adenosine deaminase.

Explanation:

ADA deficiency can be treated through gene therapy.
In gene therapy, the lymphocytes from the patient are grown outside the body and a functional ADA cDNA is introduced (using a retroviral vector) into the lymphocytes.
The genetically engineered lymphocytes are then introduced back into the patient.
These genetically engineered lymphocytes are immortal hence, the patient has to be infused with such lymphocytes regularly.

So, the correct answer is option 1.

Additional Information:

Introducing genes for ADA into the cells at early embryonic development can lead to a permanent cure for ADA deficiency.