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Hypersensitivity - Introduction (view source)
Revision as of 13:12, 18 August 2010
, 13:12, 18 August 2010Created page with "==Introduction== Hypersensitivity is a hyperactive immune response to an antigen which leads to cell and tissue damage. It involves normal immune mechanisms directed towards har..."
==Introduction==
Hypersensitivity is a hyperactive immune response to an antigen which leads to cell and tissue damage. It involves normal immune mechanisms directed towards harmless environmental antigens (ie. [[:Category:Allergic Diseases|allergy]]) or directed at self antigens (ie. [[Autoimmune Diseases - Introduction|autoimmunity]]).
These reactions are antigen specific, occurring only after the immune system has already been sensitised to that antigen. This indicates the [[:Category:Adaptive Immune System|adaptive immune system]] is involved, and such responses can be either humoral or cell mediated. Those initiated by antibodies or antibody-antigen complexes are called ''immediate'' hypersensitivity, as the symptoms are seen within hours of exposure. Conversely, the response for ''delayed-type'' hypersensitivity [[Type IV Hypersensitivity - WikiBlood|(type IV hypersensitivity)]] is not seen for days and is generally cell-mediated.
It is important to note that these responses are part of normal immune defences- in the case of hypersensitivity however the keywords are ''exaggerated'' and ''damaging''.
==Classification==
Hypersensitivity reactions can be classified according to the type of immune mechanism involved, based on a scheme proposed by Gell and Coombs over 40 years ago.
There are four main types, although a fifth has recently been added.
Types I, II and III are antibody-mediated; type IV is cell mediated.
{| border="1" cellpadding="2"
!width="150"|Time of appearance
!width="50"|Type
!width="200"|Immune mechanism
|-
| 2-30 min || [[Type I Hypersensitivity|I]] || [[IgE]] mediated
|-
| 5-8 h || [[Type II Hypersensitivity|II]] || [[IgG]] mediated: fixed antigen
|-
| 2-8 h || [[Type III Hypersensitivity|III]] || [[IgG]] mediated: soluble antigen
|-
| 24-72 h || [[Type IV Hypersensitivity|IV]] || T cell mediated
|}
==References==
Books
* Gareth Kitchen '''Immunology and Haematology''' Mosby Elsevier 2007 3rd Edition
* D.C. Blood and V.P. Studdert'''Saunders Comprehensive Veterinary Dictionary''' Elsevier Science 1999 2nd Edition
[[Category:Hypersensitivity]]
Hypersensitivity is a hyperactive immune response to an antigen which leads to cell and tissue damage. It involves normal immune mechanisms directed towards harmless environmental antigens (ie. [[:Category:Allergic Diseases|allergy]]) or directed at self antigens (ie. [[Autoimmune Diseases - Introduction|autoimmunity]]).
These reactions are antigen specific, occurring only after the immune system has already been sensitised to that antigen. This indicates the [[:Category:Adaptive Immune System|adaptive immune system]] is involved, and such responses can be either humoral or cell mediated. Those initiated by antibodies or antibody-antigen complexes are called ''immediate'' hypersensitivity, as the symptoms are seen within hours of exposure. Conversely, the response for ''delayed-type'' hypersensitivity [[Type IV Hypersensitivity - WikiBlood|(type IV hypersensitivity)]] is not seen for days and is generally cell-mediated.
It is important to note that these responses are part of normal immune defences- in the case of hypersensitivity however the keywords are ''exaggerated'' and ''damaging''.
==Classification==
Hypersensitivity reactions can be classified according to the type of immune mechanism involved, based on a scheme proposed by Gell and Coombs over 40 years ago.
There are four main types, although a fifth has recently been added.
Types I, II and III are antibody-mediated; type IV is cell mediated.
{| border="1" cellpadding="2"
!width="150"|Time of appearance
!width="50"|Type
!width="200"|Immune mechanism
|-
| 2-30 min || [[Type I Hypersensitivity|I]] || [[IgE]] mediated
|-
| 5-8 h || [[Type II Hypersensitivity|II]] || [[IgG]] mediated: fixed antigen
|-
| 2-8 h || [[Type III Hypersensitivity|III]] || [[IgG]] mediated: soluble antigen
|-
| 24-72 h || [[Type IV Hypersensitivity|IV]] || T cell mediated
|}
==References==
Books
* Gareth Kitchen '''Immunology and Haematology''' Mosby Elsevier 2007 3rd Edition
* D.C. Blood and V.P. Studdert'''Saunders Comprehensive Veterinary Dictionary''' Elsevier Science 1999 2nd Edition
[[Category:Hypersensitivity]]