CHAPTER NINE: IMMUNE DISEASE
Definitions
Immunity – _________________________________________________________________
Self-tolerance – ______________________________________________________________
Immune deficiency – __________________________________________________________
Hypersensitivity – ____________________________________________________________
Autoimmune Disease – ________________________________________________________
Introduction of Immune Disorders
Primary disease of the immune system is rare in horses. More commonly dysfunction of the immune system is a side effect of systemic infection or disease. For example, tumors or cancer in immune tissue affects the function of the immune system but the primary disease is not restricted to immune tissue. Of all the disorders affecting the immune system, equine severe combined immune deficiency disease is the only primary immune disease of note in the horse.
Equine Severe Combined Immune Deficiency (Equine SCID)
Equine SCID is a
genetic disease that affects the body’s ability to produce
antigen-specific antibodies.
Transmission is a recessive autosomal genetic trait that is hereditary.
Animals affected with equine SCID have an inherited, homozygous in the genes that allow for antibody variation. This gene codes for the enzyme VDJ recombinase, an enzyme, which catalyzes the reaction that causes variability in the V-regions of the heavy and light chains of an antibody. Without variation the antibodies are ineffective in combating antigens, leaving the affected individual with little immune defence. horses, with Arabian-crosses being carriers. Two to three percent of the Arabian horse population are homozygous for this mutation and are affected by the symptoms of disease. Approximately twenty-five percent of Arabian horses are unaffected, heterozygous carriers of the mutated gene. Equine SCID is seen most commonly in
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