Difference between revisions of "Type I Hypersensitivity"

From WikiVet English
Jump to navigation Jump to search
 
(31 intermediate revisions by 6 users not shown)
Line 1: Line 1:
−
{{toplink
 
−
|backcolour = FFE4E1
 
−
|linkpage =Immunology - WikiBlood
 
−
|linktext =IMMUNOLOGY
 
−
|sublink1 =Hypersensitivity - WikiBlood
 
−
|subtext1 =HYPERSENSITIVITY
 
−
|pagetype =Blood
 
−
}}
 
 
==Introduction==
 
==Introduction==
  
−
* Also known as IgE-mediated or anaphylactic hypersensitivity.
+
* Also known as [[Immunoglobulin E|IgE]]-mediated or anaphylactic hypersensitivity.
 
* Ranges from mild cases, such as hayfever, to life-threatening reactions, such as bee-stings.  
 
* Ranges from mild cases, such as hayfever, to life-threatening reactions, such as bee-stings.  
 
* Antigens that induce a type I reaction are known as allergens.
 
* Antigens that induce a type I reaction are known as allergens.
−
* Affects face, eyes, nose and feet
+
* Generally affects face, eyes, nose and feet
−
* IgE has a high affinity to IgE receptors on mast cells and basophils, and so binds these receptors.
+
* [[Immunoglobulin E|IgE]] has a high affinity to IgE receptors on [[Mast Cells|mast cells]] and [[Basophils|basophils]], and so binds these receptors.
−
* The individual mechanisms of cell degranulation may only have a marginal effect, but the combination can be highly effective in removing parasite infection
 
−
* Eosinophils can also target IgE bound to helminths.
 
−
** May either be attracted to the site of inflammation or produced de novo in response to cytokines.
 
−
** Binding triggers their degranulation.
 
−
*** Potent biological molecules are released.
 
−
**** Eosinophil peroxidase.
 
−
**** Eosinophil basic protein.
 
−
* This system can be invoked with inappropriate and innocuous antigens.
 
−
** E.g. pollen.
 
−
** Under these circumstances we get hay fever.
 
  
−
 
+
==Common allergens which elict a type I hypersensitivity reaction:==
−
==Common allergens:==
 
  
 
* Proteins : Foreign serum
 
* Proteins : Foreign serum
Line 38: Line 19:
 
[[Image:Sensitisation phase1.jpg|right|thumb|150px|IMAGE 1: Sensitisation phase1.jpg
 
[[Image:Sensitisation phase1.jpg|right|thumb|150px|IMAGE 1: Sensitisation phase1.jpg
 
-Brian Catchpole RVC 2008]]
 
-Brian Catchpole RVC 2008]]
−
[[Image:Immediate-type hypersensitivity.jpg|right|thumb|150px|IMAGE 2: Immesdiate-type hypersensitivity-Brian Catchpole/M Maidment RVC 2008]]
+
[[Image:Immediate-type hypersensitivity.jpg|right|thumb|150px|IMAGE 2: Immediate-type hypersensitivity-Brian Catchpole/M Maidment RVC 2008]]
  
  
Line 44: Line 25:
 
* Allergen exposure causes IgE  production.
 
* Allergen exposure causes IgE  production.
 
* IgE coat mast cells by binding to Fc receptors.
 
* IgE coat mast cells by binding to Fc receptors.
 +
* Mast cells are now sensitised to this particular allergen.
  
  
 
'''2. Subsequent exposure to the specific allergen (Image 2):'''
 
'''2. Subsequent exposure to the specific allergen (Image 2):'''
−
* mast cell degranulation.
+
* [[Mast Cells|Mast cells]] degranulate.
−
* basophils with IgE receptors are recruited and also degranulate.
+
* [[Basophils|Basophils]] with [[Immunoglobulin E|IgE]] receptors are recruited and also degranulate.
  
  
−
Mast cells secrete mediators which cause:
+
Mast cells secrete mediators:
−
* The release of inflammatary cytokines
+
* The release of inflammatary [[Cytokines|cytokines]] which can cause the dog to become itchy.
 
**Steroid mediators, e.g. prostaglandins and leukotriens
 
**Steroid mediators, e.g. prostaglandins and leukotriens
−
*Chemoattractants (attracts mainly neutrophils but also eosinophils, monocytes and basophils and plasma)
+
1. Chemoattractants (attracts mainly [[Neutrophils|neutrophils]] but also [[Eosinophils|eosinophils]], [[Monocytes|monocytes]] and [[Basophils|basophils]] and plasma)
−
*Some mast cell cytokines (especially eosinophils) release factors which promote growth and maturation of leukocytes
+
 
−
*Vasoactive and inflammatory peptides (e.g. histamine and serotonin) which causes acute contraction of smooth muscle fibres  
+
2. Vasoactive and inflammatory peptides (e.g. histamine and serotonin) which causes acute contraction of smooth muscle fibres  
−
**Leading to bronchoconstriction and vasoconstriction
+
*If the allergen is inhaled (locally) it can lead to bronchoconstriction.
−
**Violent constriction can lead to the expulsion of parasites
+
 
−
*The release of mast cell proteases
+
3. Mucus production - due to the release of mast cell proteases
−
**Promotes mucous production
+
 
−
**Inhibits parasite interactions with the epithelial surface
+
4. Vasodilation (leads to redness and heat).
−
* Vasodilation (leads to redness)
+
 
−
* Oedema (from leaky blood vessels)
+
5. Oedema (from leaky blood vessels).
  
  
 
'''3. The late phase response:'''
 
'''3. The late phase response:'''
−
* Mediated by eosinophils.
+
* Mediated by [[Eosinophils|eosinophils]].
 
* Takes longer (several hours) as the eosinophils are mobilised from the bone marrow.
 
* Takes longer (several hours) as the eosinophils are mobilised from the bone marrow.
  
Line 73: Line 55:
 
===Examples of Type I hypersensitivity===
 
===Examples of Type I hypersensitivity===
  
−
* Atopy
+
* [[Atopic Dermatitis|Atopy]]
−
* Flea allergic dermatitis
+
* [[Flea Allergic Dermatitis|Flea allergic dermatitis]]
−
* Sweet itch
+
* [[Culicoides Hypersensitivity|Sweet itch]]
 +
 
 +
 
 +
==From Pathology==
 +
 
 +
*Mediated by pharmacologically active substances from [[Mast Cells|mast cells]] and [[Basophils|basophils]]
 +
**Due to antigen-antibody (usually [[IgE]]) binding to receptors on those cells
 +
*Substances include histamine, serotonin, leukotriens, prostaglandins
 +
*Can be systemic or local
 +
*Skin becomes pruritic, raised erythematous borders of wheals
 +
*Immediate reaction
 +
*Includes:
 +
**[[Atopy|Atopic dermatitis]]
 +
**[[Urticaria]]
 +
**Angioedema
 +
**Fly bite hypersensitivity
 +
**Gastrointestinal parasites
 +
**Food
 +
*Microscopically:
 +
**Capillary dilation, oedema, mast cell degranulation, eosinophil infiltration
 +
 
 +
 
 +
{{review}}
 +
<br><br>
 +
{{Jim Bee 2007}}
 +
[[Category:Hypersensitivity]]

Latest revision as of 17:13, 17 March 2012

Introduction

  • Also known as IgE-mediated or anaphylactic hypersensitivity.
  • Ranges from mild cases, such as hayfever, to life-threatening reactions, such as bee-stings.
  • Antigens that induce a type I reaction are known as allergens.
  • Generally affects face, eyes, nose and feet
  • IgE has a high affinity to IgE receptors on mast cells and basophils, and so binds these receptors.

Common allergens which elict a type I hypersensitivity reaction:

  • Proteins : Foreign serum
  • Plant pollens : Rye grass, ragweed, timothy grass, birch trees
  • Drugs : Penicillin, sulphonamides, local anaesthetics, salicylates
  • Foods : Nuts, seafood, eggs, milk
  • Insect products : Bee venom, wasp venom, dust mites faeces, flea saliva

Mechanism

IMAGE 1: Sensitisation phase1.jpg -Brian Catchpole RVC 2008
IMAGE 2: Immediate-type hypersensitivity-Brian Catchpole/M Maidment RVC 2008


1. Initial antigen exposure sensitises immune system (Image 1):

  • Allergen exposure causes IgE production.
  • IgE coat mast cells by binding to Fc receptors.
  • Mast cells are now sensitised to this particular allergen.


2. Subsequent exposure to the specific allergen (Image 2):


Mast cells secrete mediators:

  • The release of inflammatary cytokines which can cause the dog to become itchy.
    • Steroid mediators, e.g. prostaglandins and leukotriens

1. Chemoattractants (attracts mainly neutrophils but also eosinophils, monocytes and basophils and plasma)

2. Vasoactive and inflammatory peptides (e.g. histamine and serotonin) which causes acute contraction of smooth muscle fibres

  • If the allergen is inhaled (locally) it can lead to bronchoconstriction.

3. Mucus production - due to the release of mast cell proteases

4. Vasodilation (leads to redness and heat).

5. Oedema (from leaky blood vessels).


3. The late phase response:

  • Mediated by eosinophils.
  • Takes longer (several hours) as the eosinophils are mobilised from the bone marrow.


Examples of Type I hypersensitivity


From Pathology

  • Mediated by pharmacologically active substances from mast cells and basophils
    • Due to antigen-antibody (usually IgE) binding to receptors on those cells
  • Substances include histamine, serotonin, leukotriens, prostaglandins
  • Can be systemic or local
  • Skin becomes pruritic, raised erythematous borders of wheals
  • Immediate reaction
  • Includes:
  • Microscopically:
    • Capillary dilation, oedema, mast cell degranulation, eosinophil infiltration


 This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing.




LIVE logo Originally funded by the RVC Jim Bee Award 2007
Retrieved from "https://en.wikivet.net/index.php?title=Type_I_Hypersensitivity&oldid=136025"