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

In the context of gene therapy for Adenosine Deaminase (ADA) deficiency, the patient requires periodic infusion of genetically engineered lymphocytes primarily because these lymphocytes are not immortal cells. This means that:

• Non-Immortality: Genetically modified lymphocytes do not have an indefinite lifespan. Over time, they will die off and need to be replenished.
• Recurrent Infusions: Due to their limited lifespan, patients must receive new infusions periodically to maintain therapeutic levels of functional ADA enzyme in their system.
• Production Method: In this therapy, lymphocytes are harvested from the patient's blood, genetically modified to express the ADA gene, and then reintroduced into the patient.

Options explanation:

Option	Explanation
Retroviral vector is introduced into these lymphocytes	This describes the method of gene delivery, not a reason for periodic infusion.
Gene isolated from marrow cells producing ADA is introduced into cells at embryonic stages	Unrelated to ADA deficiency therapy; embryonic interventions are not current practice.
Lymphocytes from patient’s blood are grown in culture, outside the body	This is part of the therapy process, not a reason for periodic infusions.
Genetically engineered lymphocytes are not immortal cells	Correct Explanation: Limited lifespan requires regular reinfusion.

Thus, the primary reason for the need for periodic infusions is the non-immortality of these lymphocytes.