Definition of Immunoglobulin A

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Immunoglobulin A: A major class of immunoglobulins (antibodies) found in serum and external body secretions such as saliva, tears, and sweat, as well as in the gastrointestinal, respiratory, and genitourinary tracts. Abbreviated IgA. About 10 percent to 15 percent of the antibodies present in the body are IgA antibodies.