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Where is IgA commonly found in the body?
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antibody
The four-chain structure of an antibody, or immunoglobulin, molecule. The basic unit is composed of two identical light (L) chains and two identical heavy (H) chains, which are held together by disulfide bonds to form a flexible Y shape. Each chain is composed of a variable (V) region and a constant (C) region.
IgA is the primary class of antibody found in various body secretions, serving as a critical component of the immune system at the body's interfaces with the environment. It is commonly found in:1
- Secretions: Tears, saliva, and respiratory and intestinal secretions.1
- Colostrum: The initial milk produced by lactating mothers, which provides essential protection to newborn infants.12
- Mucous Membranes: IgA is produced by B cells located within the mucous membranes and is transported to the surfaces of passages lined by these membranes, such as the gut and the respiratory tract.13
While IgA is synthesized in greater daily quantities than any other antibody class, it is present in only very low amounts in the serum. In the gastrointestinal and respiratory tracts, IgA functions by binding to microbes and toxins, preventing them from entering cells and facilitating their removal from the body. To survive the environment of the digestive tract, secretory IgA is protected from digestion by enzymes through its association with a special glycoprotein.132