![]() ![]() The appropriate planning of breeding of carriers prevents the outcome of affected foals and decreases the incidence of the mutant gene in the population. The test should be performed in all Arabian and Arabian-crossbred horses used in reproduction. The definitive diagnosis of carriers and affected foals can be done by a DNA test (VetGen, Veterinary Genetic Services, Michigan, USA) of whole blood or cheek swab samples. The mode of inheritance of the genetic defect is an autosomal recessive trait. The DNA-PK enzyme defect results from a deletion mutation of the gene encoding the catalytic subunit. The disease is caused by the lack of activity of the enzyme DNA-dependent protein kinase (DNA-PK), which is required for gene rearrangement of the antigen-receptor on B and T lymphocytes. The poor B and T cell development results in lymphopenia (less than 1,000 cells/uL), marked serum IgM and IgA deficiency, and hypoplasia of lymphoid tissues (thymus, lymph node, spleen, mucosa-associated). This fatal disease was first described in the horse by McGuire and Poppie in 1973. Essentially, children with SCID lack the ability to produce an immune system. SCID is often called bubble boy disease, made known by the 1976 movie The Boy in the Plastic Bubble. Foals are normal at birth but soon develop fatal infections, particularly when circulating colostrum-derived antibody concentrations become low. Severe combined immunodeficiency (SCID) is very rare, genetic disorder, affecting between 50 and 100 children born in the U.S. adenovirus, coronavirus, Rhodococcus equi, Pneumocystis carinii, and/or Cryptosporidium parvum). This immunodeficiency may occur in Arabian foals (or breeds carrying Arab bloodlines), and manifests clinically by susceptibility to viral, bacterial, fungal, and protozoal organisms (e.g. Once a foreign antigen is detected the immune system attacks. These invaders, called foreign antigens can be in the form of bacteria, virus, fungi, parasites or even single proteins. Severe combined immunodeficiency (SCID) is a fatal condition of both B (humoral) and T (cellular) cell dysfunction. The immune defense system is a body-wide network of organs, tissues, cells, and proteins that work together to defend the body against attacks by 'foreign' invaders. ![]()
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