Types of hypersensitivity diseases

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Types of hypersensitivity diseases

• The type of immune response and immunologic
  mechanisms that causes tissue injury
• The nature and location of the antigen that is
  the target of this response.

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Types of hypersensitivity diseases

• Immediate H.S (Type I) caused by IgE
• Type II H.S caused by antibodies other than IgE
  can cause tissue injury and interfering with
  normal cellular functions.
• Type III H.S caused by deposition of circulating
  Immune complexes in tissues
• Type IV or Delayed type hypersensitivity caused
  by T cells and Macrophages

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Disease caused by Immune responses

• Activation of Th2 cells and production of IgE
• Allergen Activation of Th2 B
  cell activation IgE binding of IgE
  to Fc receptor reexposure to Allergen
• release of mediators pathologic
  reactions

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General features (1)
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Immediate hypersensitivity

• ?? ???? ????? ? ??????? B ?? ????????? ??? ??
  ???? ??? ? ???? ???? IgE ???? ?????? .

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General features(2)

• There is a strong genetic predisposition for the
  development of immediate hypersensitivity
• high level of IgE synthesis often run in
  families
• Class II MHC alleles
• One locus for atopy is on chromosome 5,near the
  site of gene cluster encoding the IL-3,IL-4,
• IL-5,IL-9,IL-13 and IL-4R

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General features

• ????? ?????? ?? ?????? ?? ????? ????? ???? ????
  ???? ????? ???????? ??? ????? ?? ????
  ??????(pollen) ? ???? ????? ? ?????? ??????? ??
  ????? ?? ???? ?????? ?? ???? Th2 ???? ??????
• ??????? ?????????? ??? ?????? ?? ?????? ????
• ????? ???? ?? ???? ??? ????
• ??????? ?? ???? ??????? ????
• ????????????? ????

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?Allergens

• Type I is dependent on the activation of Th2
  cells
• The clinical and pathologic manifestations of
  Type Iincreased vascular permeability,vasodilatio
  n,smooth muscle contraction,local inflammation

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Mast cell activation
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Eosinophil and Basophil

• ??? ?????? ????? ?????? ??? high affinity ????
  IgE ???? FC?R ?? ?????
• ?????????? ?????????? ?? ???? ????? ?? ? ????
  ?????????? ????????????

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Mast cell activation

• Rapid release of granule contents(degranulation)su
  ch as Histamine,tryptase,chymase,proteoglycans(hep
  arin and chondroitin sulfate)
• Synthesis and secretion of lipid
  mediators(prostaglandines ,Leukotrienes)
• Synthesis and secretion of cytokines(IL-3,4,5,6,TN
  F-?)

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Mediators actions

• Histamine bronchoconstrictor,vascular
  leak,intestinal hypermotility
• PGD2vasodilator and bronchoconstrictor , neut.
  Chemotaxis
• LTC4bronchoconstriction,inflammation
• PAFbronchoconstriction ,vasodilator,
• inflammation

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??Clinical and pathologic features

• Hay fever(allergic rhinitis)
• Increased peristalsis
• Bronchial asthma
• Anaphylaxis

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Wheal and Flare reaction
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Therapy

• Inhibiting mast cell degranulation
• Antagonizing the effects of mediators
• Reducing inflammation
• Desensitization

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Anti IgE as a therapy
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Drugs

• Cromolyn sodium
• Theophyllin blocks phosphodiesterase
• epinephrin

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Prick test
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Prick test
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