IgA

biochemistry

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Last updated

June 29, 2026

Quick Summary

IgA, or immunoglobulin A, is a class of antibodies crucial for the immune system, primarily found in bodily secretions like saliva, tears, and mucus. While IgG is the most abundant immunoglobulin in the blood, the body synthesizes more IgA daily than any other antibody class.12

IgA is produced by B cells located in the mucous membranes. These molecules are joined together and associated with a special protein, enabling them to be secreted across epithelial cells lining various ducts and organs. This "secretory IgA" plays a vital role in protecting the gastrointestinal tract and other mucosal surfaces from pathogens and toxins by adhering to and neutralizing viruses and bacteria. Although present in lower concentrations in the blood serum, IgA is essential for mucosal immunity.231

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immune system
Other antibody-mediated mechanisms
The protection conferred by IgA antibodies, which are transported to the surface of mucous-membrane-lined passages, is somewhat different. Complement activation is not involved; there are no complement proteins in the lining of the gut or the respiratory tract. Here the available immune defense mechanism is primarily the action of…
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The protection conferred by IgA antibodies, which are transported to the surface of mucous-membrane-lined passages, is somewhat different. Complement activation is not involved; there are no complement proteins in the lining of the gut or the respiratory tract. Here the available immune defense mechanism is primarily the action of…
Read More

immune system
Transfer of antibodies from mother to offspring
…is very rich in antibodies—mainly IgA but also some IgM and IgG—and during the first few days of life the newborn mammal can absorb these proteins intact from the digestive tract directly into the bloodstream. Drinking colostrum is therefore essential for newborn horses and cattle and required to a somewhat…
Read More
…is very rich in antibodies—mainly IgA but also some IgM and IgG—and during the first few days of life the newborn mammal can absorb these proteins intact from the digestive tract directly into the bloodstream. Drinking colostrum is therefore essential for newborn horses and cattle and required to a somewhat…
Read More