In gene therapy of Adenosine Deaminase (ADA) deficiency, the patient requires periodic infusion of genetically engineered lymphocytes because:
1
Genetically engineered lymphocytes are not immortal cells.
2
Retroviral vector is introduced into these lymphocytes.
3
Gene isolated from marrow cells producing ADA is introduced into cells at embryonic stages
4
Lymphocytes from patient's blood are grown in culture, outside the body.