Antibodies play a key role in immune system functioning within the body. Antibodies work by binding specific factors called antigens, and there are a range of antibodies in the body that target a range of antigens. Each antibody contains two heavy chain proteins bound to two light chain proteins, which contain a variable region that differs from antibody to antibody, and governs which antigen the antibody can bind to. There are a number of types of antibodies in the human body, each with specific roles in the immune system.
IgG
Immunoglobulin G, or IgG, antibodies play a major role in protecting against infection and disease. IgG antibodies are found throughout the whole body, and they are prevalent in blood serum, accounting for around 80 percent of the total antibodies found in serum, reports Miami University. IgG antibodies can bind to foreign bacteria and viruses and target the foreign microbes for destruction by the immune system. IgG antibodies also have the ability to move into the placenta and fetus during pregnancy, so the mother's IgG antibodies can also protect the fetus from infection.
The levels of IgG in the blood are regulated by the body. High levels of IgG in the blood can indicate the presence of infection, and unexplained high IgG levels may occur as a result of another underlying disease. Low levels of IgG in the blood may leave a patient vulnerable to infection, due to a lack of antibodies available to stimulate the immune system.
IgE
Another common type of antibody is immunoglobin E, or IgE, antibodies. Unlike IgG, which activates the immune system in response to pathogens, IgE activates the immune system in response to allergens. The variable region of IgE antibodies allows for selective binding between specific IgE antibodies and specific allergens.
IgE antibody production leads to allergen sensitization, reports the World Allergy Organization. Upon initial exposure to an allergen, immune system cells produce and secrete IgE antibodies, stimulating a modest immune response. Upon re-exposure to an allergen, IgE antibodies bind the allergen and stimulate a larger immune response, leading to inflammation and other allergy symptoms.
IgA
Immunoglobulin A, or IgA, antibodies play a role in immune system functioning in mucosal tissue. Mucosal membranes line the nasal and oral cavities, respiratory system and digestive tract along with several other tissues. IgA antibodies are secreted within the mucosal lining and released to protect the mucosal lining by binding to and neutralizing foreign particles before they reach the cells within the mucosal cells. IgA antibodies may enter the bloodstream and circulate throughout the body.
IgA production can lead to the development of autoimmune diseases. IgA nephropathy occurs when IgA antibodies accumulate within the kidneys, obstructing kidney function and causing blood and protein to leak into the urine. The National Kidney and Urologic Diseases Information Clearinghouse indicates that IgA nephrology is a progressive and incurable disease, which can lead to complications such as high cholesterol.
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