|
The severe combined immunodeficiency (SCID) is a severe immunodeficiency genetic disorder that is characterized by the complete inability of the adaptive immune system to mount, coordinate, and sustain an appropriate immune response, usually due to absent or atypical T and B lymphocytes. In humans, SCID is colloquially known as "bubble boy" disease, as victims may require complete clinical isolation to prevent lethal infection from environmental microbes. Several forms of SCID occur in animal species. Not all forms of SCID have the same cause; different genes and modes of inheritance have been implicated in different species. ==Horses== Equine SCID is an autosomal recessive disorder that affects the Arabian horse. Similar to the "bubble boy" condition in humans, an affected foal is born with no immune system, and thus generally dies of an opportunistic infection, usually within the first four to six months of life. There is a DNA test that can detect healthy horses who are carriers of the gene causing SCID, thus testing and careful, planned matings can now eliminate the possibility of an affected foal ever being born.〔("SCID in Arabian Horses" )〕〔(Parkinson, Mary Jane. "SCID: An Update." from ''Arabian Horse World,'' March, 1998 )〕〔("The New DNA Test for Severe Combined Immunodeficiency (SCID) in Arabian Horses" )〕 SCID is one of six genetic diseases known to affect horses of Arabian bloodlines, and the only one of the six for which there is a DNA test to determine if a given horse is a carrier of the allele.〔AHA Equine Stress, Research and Education Committee. "Caution:Knowledge." ''Modern Arabian Horse,'' August/September 2007, pp. 100-105. Online version at http://modernarabianhorse.epubxpress.com/?site=1〕 There are other genetic diseases that affect other horse breeds,〔Other breeds known to have some individuals with genetic conditions include the American Quarter Horse, American Paint Horse, American Saddlebred, Appaloosa, Miniature horse, and Belgian.〕 and horses of part-Arabian bloodlines can be carriers of SCID. Unlike SCID in humans, which can be treated, for horses, to date, the condition remains a fatal disease.〔(FOAL.org, an organization promoting research into genetic lethal diseases in horse )〕 When a horse is heterozygous for the gene, it is a carrier, but perfectly healthy and has no symptoms at all. If two carriers are bred together, however, classic Mendelian genetics indicate that there is a 50% chance of any given mating producing a foal that is a carrier heterozygous for the gene, and a 25% risk of producing a foal affected by the disease. If a horse is found to carry the gene, the breeder can choose to geld a male or spay a female horse so that they cannot reproduce, or they can choose to breed the known carrier only to horses that have been tested and found to be "clear" of the gene. In either case, careful breeding practices can avoid ever producing an SCID-affected foal. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Severe combined immunodeficiency (non-human)」の詳細全文を読む スポンサード リンク
|