ADA Gene Therapy and Lymphocyte Treatment — NEET Biology
✅ Asked in NEET 2022The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function. The disorder is caused due to the deletion of the gene for adenosine deaminase. In some children ADA deficiency can be cured by bone marrow transplantation; in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem with both of these approaches that they are not completely curative. As a first step towards gene therapy, lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient. However, as these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes. However, if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.
NTA tests whether students understand why ADA gene therapy using lymphocytes is not a permanent cure, and why embryonic stem cell therapy would be better. The core concept: lymphocytes are somatic cells that cannot divide indefinitely, so genetically engineered lymphocytes die off and require repeated infusions. The common mistake: students confuse somatic gene therapy with germ-line therapy and think one infusion is permanent. Key point to remember: only introducing the ADA gene into early embryonic cells (germ-line modification) provides permanent cure because these cells have unlimited replication capacity. NEET frequently asks why lymphocyte therapy requires periodic infusions or compares it with embryonic approaches.
This paragraph was tested 2 times in NEET.
In gene therapy of adenosine deaminase (ADA) deficiency, the patient requires a periodic infusion of genetically engineered lymphocytes because: (NEET 2022 Phase 1)
Which kind of therapy was given in 1990 to a four-year-old girl with adenosine deaminase (ADA) deficiency? (NEET 2016 Phase 2)
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