Antibodies or immunoglobulins are present in blood and other bodily fluids, where they play a central role in the immune system. These molecules bind to foreign invaders such as bacterial proteins or toxins with incredibly high affinity and selectivity, targeting them for destruction. Antibodies are central to the body’s allergic responses and are also involved in various autoimmune diseases. Five types of antibodies have been categorized in the human body.
IGA
Mucous membranes, such as those found in the mouth, anus, ears and genital area have higher concentrations of IGA than all other antibody classes combined, according to the journal “Immunology.” There are two further subclasses of IGA: IGA1 and IGA2. IGA1 is found predominately in serum, whereas IGA2 is secreted in tears, sweat and maternal milk. IGA antibodies are involved in inflammation reactions, according to an article published in 2006 in “Veterinary Research.”
IGD
Cell membranes of a particular class of immune cell known as B-lymphocytes contain a large amount of IGD, and very small amounts of IGD are also present in blood serum. IGD is thought to play a role in activating immune cells, thereby helping the body fight pathogens, according to an article published in “Nature Immunology” in 2009.
IGE
The least abundant antibody subclass is IGE, which is found in blood serum at only 0.05 percent of IGG levels in humans, according to The University of South Carolina School of Medicine. IGE is known to play an important role in the body’s allergic response system, and abnormalities in production of this molecule are associated with a number of conditions in which the immune system becomes hypersensitized, including asthma and anaphylaxis, according to an article published in the “Journal of Allergy and Clinical Immunology” in 2009.
IGM
The primary line of defense for the immune system against pathogens in the body is IGM antibodies. These molecules are present on B-lymphocyte immune cells and are the first class of antibody to be generated when the body is exposed to an internal foreign invader such as bacteria, according to The University of South Carolina School of Medicine. IGM is found primarily in blood serum and does not diffuse into other areas of the body in large amounts due to its comparatively large size, according to an article published in the “Journal of Allergy and Clinical Immunology” in 2009.
IGG
IGG is highly abundant, comprising 75 percent of antibodies in human blood serum. These molecules are distributed evenly between tissues and the bloodstream, and are produced and secreted by blood plasma cells. IGG is part of the body’s secondary line of defense to an invading pathogen, and is synthesized in large quantities in response to immune system challenges, according to The University of South Carolina School of Medicine.
References
- PubMed; “Nature Reviews in Immunology”; Intestinal IgA Synthesis: Regulation of Front-Line Body Defenses; S. Fagarasan, T. Honjo; January 2003
- PubMed; “Veterinary Research”; The IgA System: A Comparison of Structure and Function in Different Species: V. Snoeck et al.: May 2006
- PubMed; “Nature Immunology”; Immunoglobulin D Enhances Immune Surveillance by Activating Antimicrobial, Pro-Inflammatory and B Cell-Stimulating Programs in Basophils.: K. Chen K et al.: August 2009
- PubMed; “J of Allergy and Clinical Immunology”; Immunoglobulins; Schroeder HW et al: Feb 2010
