Antibodies, also known as immunoglobulins (Ig) are a form of protein. The body produces antibodies when antigens, which are substances that can cause damage are present. Parasites, bacteria, cancer cells and viruses are examples of antigens.
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According to Medline Plus, autoimmune disorders, when the immune system accidentally attacks and destroys healthy body tissue, also result in the production of antibodies. The four types of antibodies, IgA, IgG, IgM, and IgE, all have specific functions to combat antigens in the body.
IgA antibodies protect the surfaces of the body susceptible to foreign substances. They are located in areas such as in the nose, eyes, ears, digestive tracts, tears, saliva and blood. IgA antibodies are also present in breast milk, where they are passed along to babies to help strengthen their immune system. Ten to fifteen percent of antibodies in the body are IgA.
All body fluids contain the IgG antibody. Between 75 percent and 80 percent of the antibodies in the body are IgG, yet they are the smallest. They are vital in warding off both bacterial and viral infections. IgG antibodies are the only antibodies that may pass through the placenta in pregnant women to protect the fetus.
IgM antibodies are the largest antibody, accounting for 5 percent to 10 percent of antibodies. They are found in the lymph fluid and blood. IgM antibodies are the first line of defense when an infection is detected. They help stimulate the immune system to combat foreign substances.
IgE antibodies trigger the body to respond against foreign matter like pollen, spores, pet dander and fungus. They are present in the lungs, skin and mucous membranes. IgE levels are typically high in people with allergies. They may also be present where there are allergic reactions to medicines and milk.