Over-reaction of the immune system to a harmless antigen (allergens)
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How are hypersensitivity reactions grouped?
Grouped into four types according to the effector mechanism responsible for producing the reaction
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Type I
Binding of antigen to surface IgE, primarily on mast cells. Degranulation causes the release of inflammatory mediators
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Type II
Small molecules binding to cell surface components modify the antigenicity of the molecule rendering them immunogenic. B cell response to the antigen destroys the cell
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Type III
Soluble protein antigens bind to immunoglobulin forming immune complexes. These complexes deposit on small blood vessels triggering complement cascade and inflammation
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Type IV
Antigen-specific effector T cell
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Type 1 hypersensitivity - what is the antigen, what is the effector mechanism and reaction
Type IV hypersensitivity is synonymous with what kind of reaction? What does it consist of? Example?
Delayed-type hypersensitivity (DTH), occurs 1-3 days after antigen exposure
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ex: tuberculin reaction = small amount of protein extract from m.tuberculuosis is infected subcutaneously - if immune M. tuberculosis proteins are processed, used to stimulate Th cells with then promote a local inflammatory response recruiting leukocytes at the site of injection
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(other examples : nickel allergy, poison ivy)
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Atopic dermatitis in canines and felines
Type I hypersensitivity reaction to allergens: dust mite (dermatophagoides pteronyssinus) , flour mite (dermatophagoides farinae) or saliva of flea (ctenocephalides felis)
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Treatment for atopic dermatitis
Identify allergen, prevent further exposure to allergen
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-Hyposensitization may be a good treatment for house dust mites
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Immunodeficiency results from
A defect at any stage of the immune response
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Are congenital immunodeficiencies rare?
Yes, many are X-linked and more common in males
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Complement deficiency - C3 example
Autosomal recessive - single base pair deletion in the C3 gene
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-Brittany spaniels had increased susceptibility to bacterial infection
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Inherited IgA deficiency
secreted immunoglobulin resistant to proteolytic degradation
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secretory component mediates transport across epithelial surfaces
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high affinity receptor on monocytes and neutrophils
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What condition in Irish setters is a deficiency of b-chain LFA-1 and what does it cause?
LAD (Leukocyte adhesion deficiency)
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-There is an absence of a functional LFA molecule - prevents adhesion of granulocytes to the endothelium - no migration!
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Secondary immunodeficiency following drug treatment
Corticosteriods - anti-inflammatory agent
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Increased production of IkBa - binds transcription factor NFkB preventing it from entering the nucleus and enhancing cytokine gene expression
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Cyclosporin A (secondary immunodeficiency following drug treatment)
Inhibits T cell activation by disrupting the transduction of signals from the T cell receptor
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Cancer (secondary immunodeficiency following drug treatment)
Affects rapidly dividing cells in the gut and bone marrow - causes immunosuppression
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-WBC count should be monitored
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immunodeficiency in response to viral infection - Lentiviruses (FIV, HIV,)
T helper cell depletion
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immunodeficiency in response to viral infection - FeLV
Thymic atrophy
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immunodeficiency in response to viral infection - distemper, parvo
Transient lymphocytolysis
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immunodeficiency in response to viral infection- parasite infection
Generalized immunosuppression
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Neonatal isoerythrolysis - foals
Foal's red blood cells are destroyed by antibodies in the mare's colostrum
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Inflammation
A complex, regulated yet non-specific response to physical/chemical injury or biological agent
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tumor, rubor, calor, dolor, functio laesa
The signs of inflammation in spanish; swelling, redness, heat, pain, loss of function