Term
| Immunopathology- Categories |
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Definition
-Harmful immune reactions are divided into 3 categories:
1.hypersensitiviy
2.autoimmune diseases
3.Immunologic deficiencies |
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Term
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Definition
-is an inappropriate response to an Ag resulting in a pathologic reaction on exposure to a sensitized host to that same Ag.
-they all have both an effector and sensitization phase
-sensitization phase:previous or prolonged exposure to the Ag in which an immune response is developed.
-effector phase:when inflammation and tissue damage occur.
-hypersensitivity has 4 categories (1-4)based on the mechanisms, tissues injury involved and the time until reaction after Ag exposure |
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Term
| Hypersensitivity Type 1: Immediate hypersensitivity reactions |
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Definition
-mediated by IgE expressed on the surface of mast cells, Eo and Bo.
-usually directed against environmental and parasite Ag's and tend to involve the skin, respiratory tract and GIT.
-upon exposure IgE binds to the Ag on the surface of mast cells causing degranulation and histamine release.
-types:
1.anaphylaxis: the systemic form of type 1 that usually results in hypotension, tachycardia, bronchospasm and upper airway edema.
2.Atopy: most often seen in dogs and is considered a genetic defect where there is over production of IgE in response to environmental allergens including: fungal spores, pollen, dust, grasses... Symptoms include: dermatitis, alergic bronchitis and rhinitis.
3.Feline asthma: response to inhaled allergens. It become chronic leading to chronic bronchitis and dyspnoea. |
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Term
| Hypersensitivity Type 2: Anti-body mediated reactions |
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Definition
-caused by Ab's reacting with endogenous or exogenous Ag's present on cell surfaces or in the ECM.
-mediated by IgG and IgM
-recognition results in:
1.cell lysis or phagocytosis of normal RBC's via the presence of inappropriate anti-erythrocyte Ab's. (ex. autoimmune hemolytic anemia)
2.binding of ECM proteins resulting in localized inflammation and protein breakdown (ex. epithelial intercellular junction proteins in pmphigus vulgaris)
3.cellular dysfunction, when normal cell receptors are bound by Ab's produced against the receptors (ex. muscle Ach receptors in myasthenia gravis)
-the most common type of type 2 disease involves Ab's directed against circulating RBC's
a.Autoimmune hemolytic anemia
b.Blood transfusion rections
c.Equine neonatal isoerythrolysis (or Rhesus factor babies) |
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Term
| Hypersensitivity Type 3: Immune-complex hypersensitivity |
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Definition
-reactions produce tissue damage mainly by eliciting inflammation at the site of deposition.
-Ab/Ag complexes form and circulate in the blood and get lodged in the small BV's. Once the complex is lodged, the complement system is activated and responds by eliciting inflammation to that area.
-usually an excess of Ag to Ab is need to elicit a type 3 response, therefore individuals who form low amounts of Ab to an Ag will develop immune complexes.
-examples:
1.systemic lupus erythematosus (SLE): where auto-Ab's are produced against auto-Ag's, including DNA. Glomerulonephritis,vasculitis and arthritis result.
2.Feline infectious peritonitis (FIP): a fatal, systemic disease associated with feline corona virus. Type 3 is thought to play a role in the pathogenesis of the vasculitis
3."blue-eye": involves the deposition of immune complexes in the cornea with resulting edema. It occurs in dogs immunized with live adenovirus type 1 vaccines. |
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Term
| Hypersensitivity Type 4: T-cell-mediated hypersensitivity (delayed-type or cell-mediated hypersensitivity) |
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Definition
-reactions are mediated via T-cells rather than AB's (unlike types 1-3)
-occurs when T-cells become sensitized to an Ag and release certain cytokines which activate Mo and WBC's, which release even more cytokines further perpetuating inflammation and resulting in chronic inflammation.
-require 24-48 hours to develop (due to T-cell sensitization)
-examples:
1.TB skin test: if the animal has been previously infected or is presently infected then and inflammation response will develop around the inoculation site =hyperaemic lump
2.allergic contact dermatitis: occurs in dog, horses, people and sometimes cats. The initiating chemicals are called haptens (not immunologic) but bind to Langerhans and epithelial cells = hapten-carrier complex, which are seen as foreign and attacked. (ex. plastic in food bowls and collars)
3.Tuberculosis and Johne's disease |
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Term
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Definition
-results from the loss of "self-tolerance," = immune responses mounted against "self" Ag's.
-can be: organ specific, localized or systemic.
-example = SLE (already discussed in Type 3 hypersensitivity) |
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Term
| Immunodeficiency- category 1 |
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Definition
-results when an animals' immune system fails to protect it from infectious organisms or neoplasia.
-is a result from a defect in any of the mechanisms involved in an immune response.
-Divided into 4 categories:
1.Neutrophil and macrophage defects
a.Leukocyte adhesion deficiency (LAD): autosomal recessive primary immunodeficiencies. Results in impaired expression of the recptor required for WBC diapedesis. Symptoms include, neutrophilia, impaired healing, stunted growth and recurrent bacterial infection.
b.aquired mononuclear phagocytic defects: any disorder which destroys lymphoreticular tissues (ex. viral agents and/or bone marrow)...anti-cancer drugs for one. |
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Term
| Immunodeficiency- category 2 |
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Definition
1.B-cell defects:
a.Inherited: IgA deficiency in dogs (GS's, Shar-peis, beagles) which causes increased eczema, chronic respiratory infections and allergies.
b.Aquired: lack of colostrum in neonates |
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Term
| Immunodeficiency- category 3 |
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Definition
| 1.T-cell defects: thymic aplasia will produced a defect in cell-mediated immunity and occasionally occurs in some inbred lines of dogs and cattle |
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Term
| Immunodeficiency- category 4 |
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Definition
1.Combined Immunodeficiency (B and T cells):
a.Inherited: Severe combined immunodeficiency (SCID) is an autosomal recessive disorder in which affected animals present with recurent infections (usually respiratory) as maternal Ab wanes. Symptoms include: marked peripheral lymphopenia (due to the inability to produce T and B cells) and the lack of detectable Ab in precolostral samples. Lymphoid tissues are virtually nonexistant grossly. Death occurs after a few months.
b.Acquired: caused by verious different agents, mostly viral. Includes: FeLV, Parvovirus, FIV, BVD and EHV-1. |
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Term
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Definition
-Amyloid is a pathologic proteinaceous substance which accumulates in the extracellular space.
-2 types distinguished by the type of amyloid protein:
1.Amyloid associated (AA) amyloidosis: also called "reactive systemic amyloidosis." AA protein is made in the liver and is associated with chronic inflammatory diseases.
2.Amyloid light chain (AL) amyloidosis: also called "primary amyloidosis" AL is formed from Ig light chains produced by the plasma cells and is associated with monoclonal B-cell proliferation. |
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