Question: 171: In gene therapy of Adenosine Deaminase (ADA) deficiency, the patient requires periodic infusion of genetically engineered lymphocytes because :
(1) Lymphocyctes from patient’s blood are grown in culture, outside the body.
(2) Genetically engineered lymphocytes are not immortal cells.
(3) Retroviral vector is introduced into these lymphocytes.
(4) Gene isolated from marrow cells producing ADA is introduced into cells at embryonic stages
Answer: Option (2)
Explanation:
In ADA deficiency, gene therapy is carried out by introducing a functional ADA gene into the patient’s lymphocytes.
These lymphocytes are genetically engineered outside the body and then infused back into the patient.
However, lymphocytes have a limited lifespan and do not divide indefinitely.
Since genetically engineered lymphocytes are not immortal cells, their number and activity decrease with time.
As a result, periodic infusion of these modified lymphocytes is required to maintain sufficient ADA enzyme levels in the patient.