Structure of an immunoglobulin molecule.Tizard IR, Veterinary Immunology. An Introduction, Saunders, 2001
1. Immunoglobulin G (IgG)
Immunoglobulin G (IgG) is the most abundant immunoglobulin found in the serum and is composed of two light and two heavy chains and has two binding sites. IgG also contains subunits (IgG1, IgG2, IgG3, and IgG4). It has the capacity to fix subunits of complement and the capacity to agglutinate cells. It reacts against microorganisms and toxins in extracellular fluids. It is produced later in the immune response and has a long life.
2. Immunoglobulin M (IgM)
Immunoglobulin M (IgM) is made up of five structural units formed in a circle. The five units are linked together by a chain (J chain). The immunoglobulin M has 10 binding sites. It has the capacity for strong agglutination and complement fixation. It is produced early in the immune response but stops production within a few weeks.
3. Immunoglobulin A (IgA)
Immunoglobulin A (IgA) has two distinct forms. Some IgA is found in the serum and some in secretions. 90% of serum IgA has two antigen or binding sites. The other 10% exists with four or six binding sites. Secretory IgA is found in saliva, tears, and mucuos membranes. It plays an important role in the first line of defense of the body against invading microorganisms and other foreign macromolecules.
4. Immunoglobulin D (IgD)
Immunoglobulin D (IgD) is composed of two light chains and two heavy chains. It has two binding sites. Very little is known about the function of IgD. It is found at times on the surface of B lymphocytes.
5. Immunoglobulin E (IgE)
Immunoglobulin E (IgE) is associated with allergic reactions. It is often found in elevated quantities in patients with parasitic infections. In allergic reactions IgE will be elevated from the more severe anaphylactic reactions to milder forms of allergies.
source: Immunology / Juanita A. Smith. 1995
Immunoglobulin G (IgG) is the most abundant immunoglobulin found in the serum and is composed of two light and two heavy chains and has two binding sites. IgG also contains subunits (IgG1, IgG2, IgG3, and IgG4). It has the capacity to fix subunits of complement and the capacity to agglutinate cells. It reacts against microorganisms and toxins in extracellular fluids. It is produced later in the immune response and has a long life.
2. Immunoglobulin M (IgM)
Immunoglobulin M (IgM) is made up of five structural units formed in a circle. The five units are linked together by a chain (J chain). The immunoglobulin M has 10 binding sites. It has the capacity for strong agglutination and complement fixation. It is produced early in the immune response but stops production within a few weeks.
The five subunits are held together by disulfide bonds (red). A single J chain, which has a structure similar to that of a single Ig domain, is disulfide-bonded between the tails of two μ heavy chains. The J chain is required for pentamer formation. The addition of each successive four-chain IgM subunit requires a J chain, which is then discarded, except for the last one, which is retained. Note that IgM molecules do not have hinge regions. (Source: http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mboc4&part=A4446)
Immunoglobulin A (IgA) has two distinct forms. Some IgA is found in the serum and some in secretions. 90% of serum IgA has two antigen or binding sites. The other 10% exists with four or six binding sites. Secretory IgA is found in saliva, tears, and mucuos membranes. It plays an important role in the first line of defense of the body against invading microorganisms and other foreign macromolecules.
4. Immunoglobulin D (IgD)
Immunoglobulin D (IgD) is composed of two light chains and two heavy chains. It has two binding sites. Very little is known about the function of IgD. It is found at times on the surface of B lymphocytes.
5. Immunoglobulin E (IgE)
Immunoglobulin E (IgE) is associated with allergic reactions. It is often found in elevated quantities in patients with parasitic infections. In allergic reactions IgE will be elevated from the more severe anaphylactic reactions to milder forms of allergies.
source: Immunology / Juanita A. Smith. 1995
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