Some people suffer from adenosine deaminase (ADA) deficiency. ADA is an enzyme n

Question

Some people suffer from adenosine deaminase (ADA) deficiency. ADA is an enzyme necessary for the immune systems T-cells to function properly. Helper T-cells activate B cells which secrete antibodies which are proteins that help fight against infection. When ADA is lacking due to an autosomal recessive mutation, the immune system is extremely impaired and afflicted individuals are susceptible to chronic infections. There are several different techniques that have been utilized in an attempt to treat ADA deficient individuals: Chelsea received a bone marrow transplant from her father at four months of age. His healthy cells populated her bone marrow, replacing her defective cells with normal, healthy cells that produce the needed enzyme. She is now doing quite well and has functioning T and B cells in circulation. Michael received ADA manufactured using recombinant DNA technology. Unfortunately, the enzyme stays in the blood for only a few minutes before being broken down - not long enough to restore immunity. Michael has since passed away from a fatal viral infection. Shelley was selected for gene therapy when a bone marrow donor could not be found for her. Her T-cells were separated and treated with a retrovirus which delivered a functional ADA gene to the T-cells. These T-cells were then re-infused back in to her body. Her immune system gradually began to function, but the treatment had to be repeated every few weeks as the genetically altered T-cells began to die off. Todd had gene therapy like Shelley, but it was performed on hematopoietic stem cells from his bone marrow rather than on mature, circulating T-cells. Todd soon had many normally functioning T cells and antibodies circulating in his blood for the very first time. He even grew tonsils, which are typically absent in folks with ADA deficiency. Todd's ADA activity rose to 25% of normal levels, enough to provide limited immunity. To date he hasn't required any additional gene therapy.

Shelley needed to repeat her treatment (gene therapy) where Todd and Chelsea did not because:

Shelley s treatment altered only the phenotypic deficiency not the genotypic mutation.

Shelley s treatment altered the genotypic deficiency not the phenotypic mutation.

Shelley s treatment involved germ-line therapy, which is more transient.

Shelley s treatment didn't activate the proper genes in her T-cells.

Shelley s treatment altered only the phenotypic deficiency not the genotypic mutation.

Shelley s treatment altered the genotypic deficiency not the phenotypic mutation.

Shelley s treatment involved germ-line therapy, which is more transient.

Shelley s treatment didn't activate the proper genes in her T-cells.

Explanation / Answer

The correct option is..................Shelley s treatment involved germ-line therapy, which is more transient.

ADA is an autosomal recessive disorder. Both parents have to pass a defective gene for expression of ADA deficiency in their kids.

Bone marrow transplantation from the biological match parent or from a sibling or from a matching donor could provide the healthy immune cells..................in case of Chelsea

Transfusion of haemetopoietic stem cells or the cells from which red blood cells arise also helpful in treating ADA deficiency................in case of Todd

Injecting ADA enzyme repeatedly throw enzyme replacement therapy is also useful.

Gene therapy (therapeutic genes are transferred other than germ cells) and germ line therapy (uses parents germ cells to modify the ADA gene by introducing a functional gene).

Gene therapy is introduced in case of Shelley and it is short lived. Because of multiple divisions of cells, the DNA lasts the therapeutic genes. So the patient needs multiple treatments.

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