Another form of SCID is caused by a deficiency of the enzyme adenosine deaminase (ADA), normally produced by a gene on chromosome 20. Severe combined immunodeficiency, or SCID, is a term applied to a group of inherited disorders characterized by defects in both T and B cell responses, hence the term "combined." The most common type of SCID is called XSCID because the mutated gene, which normally produces a receptor for activation signals on immune cells, is located on the X chromosome. The antibodies attack foreign substances, or antigens, that mark invading viruses, bacteria and fungi. Normally, T cells encourage other immune cells to respond to foreign substances as well as directly combat certain viral and fungal infections. Each specialized type of cell is responsible for a particular immune response. Others remain in the bone marrow where they mature into B cells and natural killer cells. Some lymphocyte precursors move to the thymus gland, where they become T cells. Lymphocytes, a type of white blood cell, are made from blood forming precursors, or "stem," cells in the bone marrow. These pioneering patients are still alive and continue to participate in on-going studies by physicians at the National Human Genome Research Institute. In addition, one form of SCID became the first human illness treated by human gene therapy in 1990, a process in which a normal gene was transferred into the defective white blood cells of two young girls to compensate for the genetic mutation. David died in 1984 following an unsuccessful bone marrow transplant, an attempt to provide him with the capacity to fight infections on his own and thus free him from the bubble.Īlthough a rare disease, SCID has been extensively studied over the past several decades because of the insights it provides into the workings of the normal human immune system. He lived in such isolators for nearly 13 years. Because David's brother had died of the disease, doctors immediately placed him into a plastic isolation unit to protect him from infections. Caused by defects in any of several possible genes, SCID makes those affected highly susceptible to life-threatening infections by viruses, bacteria and fungi. Severe Combined Immunodeficiency (SCID) may be best known from news stories and a movie in the 1980s about David, the Boy in the Bubble, who was born without a working immune system.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |