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[[Image:LH IgG.png|thumb|150px|right|'''IgG''']]

[[Image:LH IgG.png|thumb|250px|right|'''IgG''']]

[[Image:IgG.jpg|thumb|right|150px|IgG - B. Catchpole, RVC 2008]]

[[Image:IgG.jpg|thumb|right|250px|IgG - B. Catchpole, RVC 2008]]

<p>IgG is the major antibody in blood plasma and constitutes at least 80% of all antibody in the body. It is the smallest immunoglobulin so it can readily leave the blood plasma and enter tissues.</p>

 

 

IgG is the major antibody in blood plasma, and constitutes at least 80% of all antibodies in the body. It is the smallest immunoglobulin, so can readily leave the blood plasma and enter tissues. They can also cross the placenta, providing adaptive immunity to the foetus when the mother is under attack. IgG is also present in breast milk.

 

==Structure==

==Structure==

<p>IgG is Y-shaped with three constant regions and a heavy chain subunit type γ. There are several different IgG subclasses depending on the species coded for by the IGHG gene.  

 

*Ruminants have three subclasses

IgG is Y-shaped, with three constant regions and a heavy chain subunit type γ. There are several different IgG subclasses, depending on the species coded for by the IGHG gene.  

**G1-G3

 

**IgG1 is the major antibody in ruminant mucosal secretions and colostrum

'''Ruminants'''

* Dogs, rodents (and cats?) have four subclasses

 

**Dogs: G1-G4

Have three subclasses, G1-G3. IgG1 is the major antibody in ruminant mucosal secretions and colostrum.

**Rodents: G1-G3 (G2a, G2b)

 

*Pigs have five subclasses

'''Dogs, rodents and cats'''

**G1-G4 (G2a, G2b)

 

*Horses have six subclasses  

Have four subclasses. Dogs: G1-G4; Rodents: G1, G2a, G2b, G3. Cats are unknown.

**G1-G6</p>

 

'''Pigs'''

 

Have five subclasses, G1-G4 (G2a, G2b).

 

'''Horses'''

 

Have six subclasses, G1-G6.

 

==Production==

==Production==

<p>IgG is produced by plasma cells in the spleen, bone marrow and lymph nodes.</p>

 

IgG is produced by [[B cell differentiation|plasma cells]] in the spleen, bone marrow and lymph nodes.

 

==Function==

==Function==

 

*Some IgG subclasses can activate complement via the classical pathway

Some IgG subclasses can activate complement via the classical pathway. Some subclasses act as targets for [[Macrophages|macrophages]], [[Eosinophils|eosinophils]] and [[Neutrophils|neutrophils]]. It is therefore the major antibody in tissue fluids and lymph. IgG specifically binds to antigens on bacteria, causing agglutination and opsonisation.

*Some subclasses act as targets for macrophages, eosinophils and [[Neutrophils|neutrophils]]

 

** It is therefore the major antibody in tissue fluids and lymph

*IgG specifically binds to antigens on bacteria

 

**Causing agglutination and opsonisation</p>

[[Immunoglobulins|Immunoglobulins]]

 

[[Immunoglobulin A|Immunoglobulin A]]

<center><b>^{[[Immunoglobulins|Immunoglobulins]]: [[Immunoglobulin A|Immunoglobulin A]], [[Immunoglobulin D|Immunoglobulin D]], [[Immunoglobulin E - WikiBlood|Immunoglobulin E]], [[Immunoglobulin G - WikiBlood|Immunoglobulin G]] & [[Immunoglobulin M - WikiBlood|Immunoglobulin M]]}</b></center>

 

[[Immunoglobulin D|Immunoglobulin D]]

 

[[Immunoglobulin E|Immunoglobulin E]]

 

[[Immunoglobulin M|Immunoglobulin M]]

 

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