Hypersensitivity
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Questions and Answers

Define hypersensitivity

  • A normal immune reaction to an antigen
  • An increased immune reaction to an antigen that causes tissue damage (correct)
  • A genetic inability to react to antigens
  • An immune response limited to bacterial infections

    • How are hypersensitivities classified?

  • Based on antigen size
  • By the pathogen involved in the immune response
  • By the Gell and Coombs classification: Types I, II, III and IV (correct)
  • By the location of the immune response

    • What is atopy?

  • Excessive IgG production
  • Failure of B cells to produce antibodies
  • A normal reaction to an allergen
  • Excessive production of IgE caused by TH2 immunity (correct)

    • Which cytokine profile is responsible for the generation of atopy?

    <p>IL-4 and IL-13 from TH2 cells</p> Signup and view all the answers

    Which T cells are activated to produce atopy?

    <p>TH2 cells</p> Signup and view all the answers

    What is the phenotype of helper T cells involved in hypersensitivity type I?

    <p>TH2 cells producing IL-4 and IL-13</p> Signup and view all the answers

    Explain the events occurring in the sensitization phase of hypersensitivity I

    <p>Antigens are presented by APCs to CD4+ T cells, leading to the TH2 differentiation and IgE production by B cells</p> Signup and view all the answers

    Which immunoglobulins is produced in large amounts in the sensitization phase of hypersensitivity?

    <p>IgE</p> Signup and view all the answers

    Compare the levels of immunoglobulin E in serum and tissues

    <p>IgE is low in serum but high in tissues bound to mast cells and basophils</p> Signup and view all the answers

    Where in tissues is IgE located?

    <p>Bound to Fc receptors on mast cells and basophils</p> Signup and view all the answers

    What is the half-life of IgE on mast cells?

    <p>Weeks to months</p> Signup and view all the answers

    Which Fc receptors are used for binding IgE to mast cells?

    <p>FcεRI.</p> Signup and view all the answers

    Besides IgE, which other isotype of immunoglobulins can mediate a hypersensitivity 1 reaction in dogs?

    <p>IgG (specifically IgG4)</p> Signup and view all the answers

    How many IgE molecules should be cross linked for degranulation of mast cells to occur?

    <p>Two</p> Signup and view all the answers

    What molecules are released during degranulation of mast cells?

    <p>Histamine, prostaglandins, leukotrines and cytokines</p> Signup and view all the answers

    How is IgE production regulated in hypersensitivity type 1?

    <p>Through IL-4 and IL-13 production by TH2 cells and CD40 co-stimulation</p> Signup and view all the answers

    In which phase of hypersensitivity type I does the allergic reaction occur?

    <p>Hypersensitivity reaction phase (upon re-encounter with the allergen)</p> Signup and view all the answers

    Apart from mast cells, which other cells can degranulation during a hypersensitivity type I reaction, thus contributing to the clinical presentation?

    <p>Eosinophils and basophils</p> Signup and view all the answers

    What role does histamine play in an allergic reaction?

    <p>Acts as a vasodilator and increases vascular permeability, causing symptoms like itching and swelling</p> Signup and view all the answers

    Why are allergies sometimes managed with administration of antihistamines?

    <p>To inhibit histamines effects on tissues, reducing symptoms like itching and swelling</p> Signup and view all the answers

    Why would you recommend a corticosteroid to manage some allergies?

    <p>To suppress the immune response and reduce inflammation caused by hypersensitivity</p> Signup and view all the answers

    Do memory responses exist in hypersensitivity type I?

    <p>Yes, memory B and T cells are involved, contributing to faster responses upon re-exposure</p> Signup and view all the answers

    What is anaphylaxis?

    <p>A generalized, potentially life-threatening allergic reaction involving multiple systems</p> Signup and view all the answers

    What events can lead to anaphylaxis?

    <p>Large does of antigens entering the body rapidly, often intravenously</p> Signup and view all the answers

    What is the anaphylactic shock organ in dogs?

    <p>Liver</p> Signup and view all the answers

    Outline the symptoms of anaphylaxis in animals

    <p>Difficulty breathing, collapse, vomiting, diarrhea and swelling of tissues</p> Signup and view all the answers

    How can allergic reactions to own milk develop in cattle?

    <p>By absorption of milk proteins like alpha-casein into the blood stream due to inadequate milking</p> Signup and view all the answers

    A dog owner claims their pet Fido developed an allergic reaction after drinking decaf coffee for a week. Do you agree? Why or why not?

    <p>No, allergic reactions typically require prior sensitization, and the symptoms might be due to food intolerance or another cause</p> Signup and view all the answers

    What is the difference between a food allergy and food intolerance?

    <p>Food allergies are immunological reactions, while food intolerance results from toxic effects of food metabolites</p> Signup and view all the answers

    Describe a diagnostic test you could perform to determine the allergen causing the allergy

    <p>Conduct intradermal skin testing with diluted allergen solutions</p> Signup and view all the answers

    If an animal is being treated for skin allergies with immune suppressants and anti-vascular permeability medicines, what precautions would you take to ensure that your allergy skin test works well?

    <p>Discontinue immune suppressants and anti-vascular permeability medicines before testing</p> Signup and view all the answers

    If you were considering serology for allergy diagnosis, which immunoglobulin would you target?

    <p>IgE</p> Signup and view all the answers

    What’s the best medicine that can completely cure an allergy?

    <p>Avoidance of the allergen</p> Signup and view all the answers

    What’s the principle behind the desensitization approach to managing allergies ?

    <p>Gradually increasing allergen exposure to reduce IgE levels and increase IgG production</p> Signup and view all the answers

    What’s the mechanism of hypersensitivity type II?

    <p>IgG and IgM antibodies bind to antigens on cell surfaces, leading to cell destruction via complement, ADCC, or phagocytosis</p> Signup and view all the answers

    Which immunoglobulins play an important role in Type II hypersensitivity?

    <p>IgM and IgG</p> Signup and view all the answers

    Describe three ways tissue destruction can occur during type II hypersensitivity

    <p>Complement activation, ADCC by NK cells, and phagocytosis by macrophages</p> Signup and view all the answers

    How does the hemolytic disease of the newborn (HDN) develop in horses?

    <p>When maternal antibodies against fetal RBCs are transferred to the foal through colostrum</p> Signup and view all the answers

    What conditions must be met for HDN to occur in a newborn foal?

    <p>The fetus must inherit antigens not present in the mother, the mother must be sensitized to these antigens and the foal must ingest colostrum containing anti-RBC antibodies</p> Signup and view all the answers

    A horse is treated with trimethoprim for a respiratory infection. Four weeks later, it develops a bleeding condition with anemia. Diagnostic tests reveal high levels of antibodies against platelets and RBC. What this the likely cause and mechanism?

    <p>Drug-induced type II hypersensitivity, where the drug modifies RBC and platelet surfaces, triggering antibody-mediated destruction</p> Signup and view all the answers

    Do you know any infections that can lead to a hypersensitivity type II reaction?

    <p>Streptococcus spp, infectious anemia virus, Aleutian disease virus, Rickettsia, Trypanosomes</p> Signup and view all the answers

    In dogs and horses, how does rheumatic heart disease develop after infection with streptococcus spp?

    <p>Through cross-reactivity where antibodies against Streptococcus spp antigens attack heart tissue antigens, leading to chronic inflammation and damage</p> Signup and view all the answers

    When too many antigen-antibody (Ag/Ab) complexes accumulate in the body, what inflammatory condition results?

    <p>Type III hypersensitivity, leading to tissue damage from immune complex deposition</p> Signup and view all the answers

    Give examples of diseases associated with hypersensitivity type III

    <p>Immune complex glomerulonephritis, Rheumatoid arthritis, serum sickness, subacute bacterial endocarditis, symptoms of malaria, systemic lupus erythematosus and Arthus reaction</p> Signup and view all the answers

    Which immunoglobulins are responsible for hypersensitivity type III?

    <p>IgG and IgM</p> Signup and view all the answers

    Depending on the lactation of Ag/Ab complex deposition, what two types of hypersensitivity type III can be differentiated?

    <p>Localized (antibody excess) and generalized (antigen excess)</p> Signup and view all the answers

    What type of lesions would you expect to see in the skin with local reaction of a hypersensitivity type III?

    <p>Redness, edema, bleeding, and thrombosis at the injection site</p> Signup and view all the answers

    What is the phenomenon : Arthus reaction?

    <p>A localized, painful, swollen area that occurs under the skin after an injection</p> Signup and view all the answers

    What can be the cause of “blue eye” in dogs?

    <p>Deposition of immune complexes in the cornea following infections with canine adenovirus type 1 or vaccination with live adenovirus vaccine</p> Signup and view all the answers

    What is serum sickness ?

    <p>A type III hypersensitivity resulting from antibodies against serum proteins introduced intravenously</p> Signup and view all the answers

    What important disease is associated with serum sickness?

    <p>Membranoroliferative glomerulonephritis</p> Signup and view all the answers

    What type of hypersensitivity is purpura hemorrhagica?

    <p>Type III hypersensitivity</p> Signup and view all the answers

    Is it possible for dietary hypersensitivity type III to develop? How does it develop?

    <p>Yes, it develops when food proteins are absorbed into the bloodstream and form immune complexes, causing tissue damage</p> Signup and view all the answers

    What’s the hallmark of Type IV hypersensitivity?

    <p>T-cell mediated delayed inflammation, typically occurring in 48-72 hours after antigen exposures</p> Signup and view all the answers

    What is delayed type hypersensitivity (DTH)?

    <p>A hypersensitivity reaction mediated by T cells and macrophages occurring 24-72 hours after exposure</p> Signup and view all the answers

    How long does it take for hypersensitivity type IV to develop?

    <p>24-72 hours</p> Signup and view all the answers

    What is tuberculin used for in animal and human diagnostics?

    <p>As a skin test to diagnose tuberculosis via a type IV hypersensitivity reaction</p> Signup and view all the answers

    Contact hypersensitivity is important in dogs. Mention the possible causes of this condition

    <p>Chemicals such as formaldehyde, dyes, flea collars, and shampoos acting as haptens</p> Signup and view all the answers

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