Immunoglobulin G

Revision as of 16:27, 12 June 2010 by A.allison (talk | contribs) (Text replace - 'Immunoglobulin M - WikiBlood' to 'Immunoglobulin M')



Shortened to IgG

IgG
IgG - B. Catchpole, RVC 2008

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.

Structure

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
    • G1-G3
    • IgG1 is the major antibody in ruminant mucosal secretions and colostrum
  • Dogs, rodents (and cats?) have four subclasses
    • Dogs: G1-G4
    • Rodents: G1-G3 (G2a, G2b)
  • Pigs have five subclasses
    • G1-G4 (G2a, G2b)
  • Horses have six subclasses
    • G1-G6

Production

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

Function

  • Some IgG subclasses can activate complement via the classical pathway
  • Some subclasses act as targets for macrophages, eosinophils and neutrophils
    • It is therefore the major antibody in tissue fluids and lymph
  • IgG specifically binds to antigens on bacteria
    • Causing agglutination and opsonisation



Immunoglobulins: Immunoglobulin A, Immunoglobulin D, Immunoglobulin E, Immunoglobulin G & Immunoglobulin M