Adenosine deaminase (ADA) deficiency is a hereditary disease, where ADA, which is crucial for functioning of immune system is absent. Ex plain how ADA deficiency can be treated.

Explanation

The right approach for SCID treatment would be to give the patient a funetioning ADA which breaks down toxic biological products.
In some children ADA deficiency could be cured by bone marroW transplantation, wher. defective immune cells could be replaced with healthy immune cells from a donor. In some patients it can be treated by enzyme replacement therapy, in which functional ADA is injected into the patient.
During gene therapy the lymphocytes from the blood of the patient are removed and grown in a utrient culture medium. A healthy and functional human gene, ADA cDNA encoding this enzyme is introduced into the lymphocytes using a retrovirus. The genetically engineered lymphocytes are subsequently returned to the patient. Since these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes. The disease could be cured permanently if the gene for ADA isolated from bone marrow cells are introduced into the cells of the carly embryonic stages.