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Gene therapy involves transferring good genes into cells to replace harmful genes. There are two specific types: genes transferred into germ line cells (reproductive cells) and genes transferred into somatic cells (body cells). In somatic gene therapy, altered genes are inserted into the affected part of the body, or body cells are removed, treated with altered genes, and replaced. People using this kind of therapy include patients with diseases such as cancer, hemophilia, cystic fibrosis, and muscular dystrophy. Positive aspects patients may expect include health benefits, safety, and less ethical concerns than germ line gene therapy, but negative aspects may include lifetime treatments and problems with gene delivery.
Doctors can conduct somatic gene therapy in vivo or ex vivo. With in vivo therapy, doctors transfer the altered gene directly into the body, usually into the tissue. For example, genes are inserted into the skin for patients with skin cancer and into the muscles for patients with muscular dystrophy. For the ex vivo technique, doctors often remove afflicted cells, blood cells, or bone marrow cells from the patient’s body. After inserting the desired gene into the cells, they are injected back into the body.
One of the leading pros of somatic gene therapy is also a con: People who undergo somatic gene therapy do not pass on the altered genes to their offspring because only body cells are modified, not reproductive cells. This is positive because there are no ethical concerns about tampering with natural infant development as in germ line gene therapy. In fact, gene therapy on reproductive cells is prohibited in some countries. However, the inability to pass down altered genes can be negative because the beneficial effects of somatic gene therapy stop at the patient, preventing the possibility of passing down health benefits to future generations.
Other pros of somatic gene therapy include safety in comparison with germ line gene therapy and the potentially life-changing health benefits in the patient. Possible cons of somatic gene therapy include temporary effects and complications during gene delivery. People who receive somatic gene therapy often need treatments for the rest of their lives because the body tissue cells, in which the genes were inserted, eventually are lost. Furthermore, the viruses that gene therapists use to insert genes into cells can sometimes cause an accidental immune system response. There is also the possibility that gene carriers alter the wrong genes.