Forms of Gene Therapy

Gene therapy takes two broad forms. (a) Germ-line gene therapy introduces healthy genes into germ cells -- sperm, eggs, or early embryos -- so that the corrected genetic information is transmitted to the next generation. Although this is highly effective at counteracting a genetic disorder, it is not encouraged for use in humans, for a mix of technical and ethical reasons.

(b) Somatic-cell gene therapy introduces the gene only into somatic cells -- for example bone-marrow cells, hepatic cells, fibroblasts, endothelium and pulmonary epithelial cells, central-nervous-system cells, endocrine cells, or the smooth muscle cells of blood-vessel walls. Because this modification affects only the treated individual and cannot be passed on to future generations, somatic-cell gene therapy is the only currently feasible clinical option, and trials have already been carried out for acquired disorders such as cancer, rheumatoid arthritis, and blood disorders including SCID, …