Hypersensitivity Reactions

Type 1) Immediate
1. Stage 1: Sensitization. Under normal curcumstances- IgM would be produced with APC production but release of IL4 (and some genetic predispositions) will promote an isotypic switch to IgE antibodies
  1. Stage 2: The activation stage: There is X reaction between the allergen and IgE which are located on MAST cells- degradation
    1. Stage 3: Effector stage: Degranualtion releases pharmocologically activ particles: chemokines, vasoactive and chemoactive molecules as well as enzymes which promote inflammation
2. Atopc dermatits, milk allergy in Jersey cows, Mites and Penicillins
Type 2
1. This is when there are Ig's binding to normal cells and causing destruction via ADCC and complement cascades.
  1. IgG bind to ACH receptors of the oesophagus causing MegaE (Myasthenia Gravis
  2. IgG bind to platelets causing thrombocytopenia
  3. Maiden mares who are exposed (and develop Ig) to their foal (father inherited) antbodies during pregnancy. These Ig's are then passed into colustrum and cause neonatal jaundice
Type 4) Delayed
1. **These DO NOT INVOLVE ANTIBODIES**- No B cells
2. This is when an antigen in inoculated into the skin and a SLOW (2-3d) inflammtory reponse is actvated
  1. 1) The antigen migrates to local LN and APC'S are activated as the pathogen is processed and presented
    1. 2) The T cells and NK cells travel to the inoculation site and induce inflammation
      1. Allergic contact dermatitis occurs when certain chemicals/ toxins are absorbed into the skin
      2. M. TB testing in cattle- a positive tuberculin test occurs if the animal has had prior exposure
Type 3
1. This is an immune COMPLEX mediated reaction where a large number of [Ig-Ab] activate the complement system
  1. In normal circumstances these complexes are either phagocytosed or taken up by liver kuppfer cells for destruction. In these cases the antigen is chronic via... 1) Persistent infection, 2) An auto-immune issue or 3) An inhaled antigen
    1. Rheumatoid arthritis
    2. The ARTHUS response to vaccinations- this is a local issue which is common in cats
    3. Serum sickness: This is a sytemic response to passive immunization which may induce vascuitism edema and swelling of joints/ LN's
These have been characterised into 4 types- all activated by an ALLERGEN, those that become systemic are anaphylactic.. Pollen, fish, penicillin, Brazil nuts etc
1. Benefits include the release of chitinases which degrade insects, fungi etc

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Hypersensitivity Reactions

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	Erstellt von rpbardoul vor fast 9 Jahre